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Abstracts - Nice 2006
Antenna mutual coupling effects on correlation, efficiency and Shannon capacity in MIMO wireless systems
A. Stjernman
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MIMO (multiple-input-multiple-output) systems make use of multiple antennas at both ends of a communication link to exploit the spatial dimension for increasing the capacity. Correlation of the antenna signals has an affect on the capacity of a MIMO implementation. High correlation levels occur mainly for compact antenna realizations, where the separation of the antenna elements is small and the mutual coupling is strong. The antenna mutual
coupling distorts the antenna radiation patterns and the input impedances, and therefore affects the correlation level and the efficiency. The correlation level is decreased by coupling, which would improve the Shannon capacity, but the effiency of the antenna system is also decreased, which leaves the Shannon capacity nearly unchanged as compared to the case when neglecting coupling effects. The Shannon capacity is increased in a interference limited receiving situation and can also be increased in a transmitting situation in a narrow frequency band by using a decoupling network.
Low profile mobile scanning phased array antenna system for DBS reception
M. Gachev, S. Kamenopolsky, E. Totomanov, V. Boyanov, B. Marinov, I. Ivanov
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The paper presents circularly polarized scanning phased array antenna terminal, developed for ground DBS reception in the frequency band 12.2 – 12.7GHz. Design of the antenna utilizes microstrip printed circuit technique to achieve thin flat profile of the product, easy manufacturing and compatibility with MMIC phase control devices. The array is electronically steerable in elevation, as the phase control is realized with 5-bit phase shifters. Scanning in azimuth angles is mechanical. Amplitude control is not applied. The grid shape and spacing are considered to cover large tilt
angles (up to 65deg). Radiating elements are circular probe-fed patches. The antenna is purposed to the ground mobile users and provides hand over from beam to beam, depending on which particular beam provides the best link margin. Main components and blocks of the antenna terminal are discussed in the proposed paper, including radiating element, feed network, vertical structure, microstrip layers, LNA design, beam coverage.
Measured antenna patterns and parameters are presented.
Multireflector dipole antennas
I. Hertl, Z. Raida, L. Oliva
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The paper presents principle and design of multireflector antennas. The structure consists of printed dipole antenna and cascaded planar reflectors made with the technology of frequency selective surfaces. Several types of frequency selective surfaces used as reflectors are compared in the paper to achieve best suiting properties. Also different modifications of printed dipole antenna including one with fractal elements are described and discussed. Feeding and the impedance matching are performed using standard wideband balun.
Ultra-wideband antenna with switchable band-notched behavior
E. Antonino-Daviu, M. Ferrando-Bataller, M Suarez-Fabres, C. Suarez-Fajardo
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In this paper, a compact ultra-wideband (UWB) planar monopole antenna with a switchable band-notched behaviour is proposed. The antenna switching performance is achieved by means of a square loop slot loaded with a silicon PIN diode. An initial prototype with a switchable band reject function at 5.8 GHz has been fabricated and evaluated, obtaining good results.
Transient response optimization of ultra wideband antennas (using Particle Swarm Optimization)
P. Cerny
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For some ultra wideband applications (i.e. radar, positioning, etc.), it is crucial to know the transient responses of antennas. Optimization process searches for the dipole shape, which accomplishes two required parameters - namely good matching and minimal distortion. The dipoles have derivative characteristics. The distortion is evaluated from the derivative of the excitation impulse with the radiated impulse. The particle swarm optimization method was used in the process of optimization. This method was implemented in MATLAB®, where the antenna structure is generated. The antenna is subsequently simulated in the CST Microwave Studio®. The optimized ultra wideband dipole is perfectly matched and minimally distorts the applied signal.
Lumped high-low pass balun for ultra wide band printed balanced antennas
V. González-Posadas, D. Castro-Galán, J.L. Jiménez-Martín, D. Segovia-Vargas, C. Martín-Pascual
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A semi-lumped balun transformer for UHF dipoles is reported in this paper. The proposed structure utilizes two filters plus one small transmission line. This circuit does not require any multilayer either suspended substrates techniques. Its broadband behaviour is due to the use of lumped elements; this is particularly useful for low microwave band. The key idea is to use a geometrical progression for the characteristic line impedance and extract the values of the lumped elements from those values. Several baluns have been built to demonstrate the electrical feasibility in wideband UHF dipoles. Finally, a broadband monopole is attached to the balun to show its performance.
Application of Vilenkin's addition theorem in the analysis of spherical antennas and periodic structures
Z. Sipus, S. Skokic
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This article demonstrates a novel approach to the mutual coupling calculation within the Moment Method (MoM) analysis of spherical arrays. By expressing the patch/dipole current in terms of two suitable potentiallike auxiliary functions, it is possible to avoid the use of Euler’s formulas for coordinate system rotation and the related lengthy integrations. Instead, the rotation in ?- direction can be done in closed form with the help of
Vilenkin’s additional theorem for associated Legendre functions. It is shown that the new approach results in significant acceleration of the analysis of both spherical antenna arrays and frequency selective surfaces. The algorithm is validated by comparing the results to the measurements performed on the developed laboratory model.
Monopulse scanning beam planar array for signal identification system
C. Domínguez-Grano-De-Oro, J.L. Masa-Campos and M. Sierra-Pérez
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An antenna for a Signal Identification System has been designed. The objective of this design is to detect the angle of the arrival signal by electronic sweeping and a monopulse system in the horizontal plane. The antenna frequency performance is fixed at 1.06 GHz with an 80 MHz bandwidth (7.54 %). A ±60º sweeping of the aiming angle signal with a 3 dB loss level in the edges is desired, as well as a 22 dB maximum gain of the total antenna, but the minimum coverage is ±45º. For all these reasons, a planar array antenna is designed with a number of 40 radiating elements and divided into 10 columns and 4 rows. Each column is connected to a phase shifter and all columns are fed through a hybrid stripline network.
Slot array fed by an oversized TEM waveguide
E. Alfonso, A.-V. Nogueira, J.I. Herranz, V.-M. Rodrigo-Peñarrocha
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We propose a novel slot-array antenna fed by a new guiding structure which forces a quasi-TEM mode within an oversized rectangular waveguide using a hard surface on the bottom face of the waveguide. In this paper, our objective is the evaluation of the order of magnitude of slot internal mutual coupling, as well as its interaction with the propagating quasi-TEM mode. This study can allow us to use a simplified model to analyse the whole slot array. Simulation results are shown.
Circular array for GSM-UMTS application
C. Suárez-Fajardo, M. Ferrando-Bataller, E. Antonino-Davio, F. Vico-Bondia
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The switched beam antenna, a smart antenna technology, consists of an array of antennas, a beamforming network and a switching matrix. It may be used to generate n beams to improve the carrier to interference ratio (CIR) and the reuse of frequency in cellular systems, increasing system capacity.
New topologies of radial-line slot-dipole array antennas
J.I. Herranz-Herruzo, A. Valero-Nogueira, E. Alfonso-Alós, D Sanchez-Escuderos
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This paper proposes new topologies of linearly polarized radial-line slot-array antennas (LP-RLSA) which uses slot-dipole pairs as radiating elements. Firstly, the basic design of the antenna with cancelling slots is considered and its benefits and drawbacks are highlighted. The evolution of this configuration leads to more convenient arrangements of the radiating and cancelling elements. Finally, a LP-RLSA composed of doubled rings demonstrates to be the most suitable topology for this kind of antennas.
A dual-band dual-polarized Ka-Ku printed array
E. Arnieri, L. Boccia, G. Amendola, G. Di Massa
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This paper investigates the possibility to realize dual band Ka-Ku arrays using low cost PCB technology. As a possible solution, a dual band array composed of Inverted Shorted Annular Patch antennas interleaved with circular waveguides is here presented. Full wave simulations are presented to prove the validity of the proposed solution.
Optimization of Resonant-Cavity Antenna
A.R. Djordjevic, A.G. Zajic
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An optimized low-profile antenna that consists of a rectangular resonant cavity and nonuniform radiation slots is presented. The antenna has a pencil-beam radiation pattern, low sidelobes, and can handle two orthogonal polarizations. The antenna design is verified by simulations and experimental results.
Experimental investigation of the mutual coupling reduction through cavity enclosure of patch antennas
I.E. Lager, M. Simeoni
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The mutual couplings between patch antennas printed on a common dielectric board is evaluated experimentally. Two variants of this type of radiators are taken into account: with and without a cavity enclosure of the patches. Experiments are conducted on patch antennas manufactured
in a standard printed circuit board (PCB) technology. The presence of cavities, fabricated by means of equally-spaced, metal-plated through-holes surrounding the antennas, reduces the amount of energy flowing from one radiator to another.
Gain enhancement methods for microstrip patch antennas
M. Kamaszuk
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This paper presents the results of my research on the use of gain enhancement methods for microstrip patch antennas. Special attention was given to novel material technology – photonic bandgap structures (PBG). I considered also stacked microstrip antennas with parasitic patch, with dielectric superstrate and antennas with slotted ground plane. Interest in concepts considered bulky, such as dielectric lenses, were abandoned during the course of the research. Comprehensive electromagnetic simulations were performed with the goal of a gain enhancement with a single patch element. The most interesting antennas were examined experimentally.
Microstrip patch antenna with compact feed to reduce harmonics
L. Inclan-Sanchez, J.L. Vazquez-Roy, E. Rajo-Iglesias
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In this work, a new method to suppress the harmonic radiation from an square electromagnetically coupled microstrip patch antenna is proposed. The goal of the design is the elimination of the resonances at the 2nd and 3rd harmonic frequencies to reduce spurious radiation due to the corresponding patch modes. The study shows the possibility of controlling the second harmonic resonance matching by varying the lenght of the feeding line. In addition a resonator is placed underneath the antenna’s feeding line order to suppress the third harmonic. It consists of a printed metallization with a via connected to the ground plane (mushroom type) in a multilayer configuration. This feature could be advantageous in a transmitting active patch antenna to eliminate the harmonic radiation.
Evaluation of MIMO arrays using antenna patterns, reverberation chamber, and channel measurements
B. Lindmark, L. Garcia-Garcia, N. Jaldén, C. Orlenius
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We have compared different methods of evaluating arrays for MIMO systems. We calculated the MIMO capacity of a compact antenna array for mobile or WLAN applications at 1766 MHz and compared it to a large reference array of 4 monopoles. Three different methods were used: evaluation using radiation patterns and a channel model, measurements in a reverberation chamber, and simultaneous measurement of radio channel data using the two arrays. We conclude that the main difference in the to arrays is the 1.3 dB lower efficiency of the compact array.
Design of compact loop-wire medium at radio frequencies for magnetic resonance imaging
X. Radu, S. Massaoudi, D. Dancila, I. Huynen, C. Craeye
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In this paper we show how a loop wire medium can allow to tune the index of refraction of metamaterial. The principle and a equivalent circuit are presented in a first time. Then, in order to show the influence of the helix geometric parameters on the plasma frequency, simulations of loop wire medium based on the method of moments (MoM) are carried out. Comparisons with the classical wire medium show a decrease of the plasma frequency. In a second step, simulations of the loop wire medium, combined with a negative permeability structure are carried out, to show their influence on the negative index of refraction: extraction of the negative index of refraction shows a decrease of this one, in the presence of medium with high inductance.
Design of a non-periodic artificial magnetic conductor to obtain a high-gain low-profile antenna
R.M. Mateos, C. Craeye, G. Toso
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The narrow bandwidth of artificial magnetic conductors (AMC’s) limites their use in broadband applications. Besides this, when trying to increase the bandwidth of antennas based on high-impedance surfaces, the radiation pattern tends to split at broadside when approaching the resonance frequency of the AMC used as a ground plane. A study on the surface currents on the patches evidences that the currents induced on contiguous patches are not in phase, which may lead to the cancelation of their E- field contributions. In this paper, the dependence of this phase shift versus frequency and patches dimensions is analyzed with the help of an eigenmode analysis based on the Method-of-Moment (MoM) technique. Reducing
the size of the AMC in the E-plane and breaking its periodicity in the H-plane improves the broadside directivity.
Miniaturisation of conventional radio-link reflector antennas by using of active arrays
D. Segovia-Vargas, J. Segador, L. Fernandez-Martinez, L. Inclan, V. Gonzalez-Posadas
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Using of active array antennas has been shown as a suitable technique to improve the figure of merit (G/T) of a radio-link, increase the effective gain or make a better distribution of the power what can reduce the number of amplifiers used in the feeding network [1]- [2]. As one of the characteristics of active antennas is that it can improve the effective gain, a trade-off between the increase of effective gain and the reduction
of antenna size can be done. The effect of including active elements to increase the effective gain while maintaining the radio-link gain implies a reduction in the antenna size. The paper presents the reduction that can be achieved in the antenna size by using of an active array. A study of the level of active element integration (patch level or subarray level) has been done to obtain the optimum situation between the size reduction factor and the power associated to any of the amplifiers in the active array.
Green's functions for planar structures in periodically skewed 2-D lattices using Ewald transformation
I. Stevanovic, J.R. Mosig
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In this paper, we apply the Ewald acceleration technique to the efficient evaluation of periodic Green’s functions (GFs) for 2-D skewed lattices. We develop the expression for the optimal value of the splitting parameter for 2-D skewed lattices, derive the gradient of the scalar potential GFs and address the extraction of singularity for both vector/scalar potential GF and their curl/gradient. Several numerical implementation issues are also discussed leading to further enhancement in computational speed, accuracy, and numerical stability.
Dual-band CRLH ring antenna with linear/circular polarization capability
A. Rennings, S. Otto, T. Liebig, C. Caloz, I. Wolff
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A dual-band metal-insulator-metal (MIM) composite light/left-handed (CRLH) ?-resonance ring antenna with multi-polarization (linear/circular) radiation capability is demonstrated by way of full-wave simulations. The theory, design guidelines, parameter extraction procedure and feeding structure of this antenna are presented and discussed.
New toroidal antennas for WLAN communications: Validation of two prototypes
J.C. Brégains, G. Franceschetti, A.G. Roederer, F. Ares
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Some new antennas that radiate linearly polarized toroidal beams are presented. Two prototypes have been constructed. Their design procedure is based on the use of a Method of Moments commercial software tool. Very accurate toroidal beams are obtained with large operating relative bandwidths -up to almost 24% in one of the models. Fairly good agreement between calculations and measurements were obtained.
Design of high gain slotted waveguide antenna using metamaterials
X. Dardenne, C. Craeye, A.O. Boryssenko
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Numerical simulations of antennas based on periodic metamaterials fed by a slotted waveguide can be excessively time consuming because of the large number of unknowns involved in such structures. This paper depicts how the analysis of the metamaterial can be carried out separately from the waveguide by defining interior and exterior equivalent problems. Moreover, we will show how the combination of both equivalent problems allows a fast computation of the antenna impedance properties. Finally, a method resorting to infinite array simulations and the Array Scanning Method (ASM) is presented that allows a very efficient analysis of the periodic superstrate in the exterior problem.
A unified approach to model planar multilayered structures with lateral perfect electric/magnetic and periodic boundary conditions
P. Crespo-Valero, I. Stevanovic, J.R. Mosig
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This communication proposes a simple approach to model planar multilayered structures based on an Integral Equation technique. This method is applicable to a wide range of practical boundary conditions and basis functions while keeping a simple formulation in all cases. The technique is based on the modal representation of the Green’s function in a laterally bounded media (e.g. waveguides or periodic structures) and reduces the surface integrals to simple line integrals over contour of the basis function’s domain. The final formulation presents important advantages due to its generality, simplicity and efficiency.
Quick SAR assessment using dual-plane amplitude-only measurement
J. Fridén, M. Siegbahn, B. Thors, L. Hamberg
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Current standardized procedures for measurements of the Specific absorption rate (SAR) of mobile phones and radio base station antennas include a volumetric scan of the electric field strength induced in a head or body phantom. Assessment of multi-band and whole-body SAR requires repeated volumetric scanning over a large part of the phantom and is time-consuming. In order to reduce the total evaluation time, different methods have been proposed to estimate the SAR from measurement data based on sparse volumetric scanning and surface scanning.
These methods rely on data fitting with underlying assumptions about the spatial distribution of the fields. In order not to be biased by previous or current antenna design, and to be able to use currently available assessment systems, a model-independent dual-plane-scan method is investigated based on amplitude measurements of the electric field components. The amplitude of the electric field components are measured in two planes close to the phantom surface, and the phase is recovered using an iterative process. The plane wave spectrum of the resulting
complex electric field components is then used to propagate the field into the phantom. The measurement time is typically reduced by a factor 5 and in some cases even more. Furthermore, the plane wave spectrum is utilized for fast calculation of the mass-averaged local SAR values.
A numerical tolerance study, using single and multipeak fields with relevant errors superposed, is performed to demonstrate the robustness of the method. The resulting errors in the estimated SAR values are below 1% for realistic positioning errors and signal to noise ratio. Comparisons
with measurements in a flat phantom are also made. Moreover, the underlying algorithm can be applied to curved surfaces.
A measurement system for determining radiation efficiency of a small antenna
P. Kabacik, A. Byndas, R. Hossa, M. Bialkowski
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The paper describes a system for measuring radiation efficiency of a small antenna operating alone or in the presence of objects similar to those as in an actual service. The system applies the direct approach to determining the antenna efficiency by measuring the radiated field over the entire sphere surrounding the tested antenna. In order to overcome problems associated with the conventional measuring equipment, the antenna under test is equipped with a miniature built-in VCO signal generator and supported by a low reflectivity dielectric positioner. The positioner is of sufficient size and strength to hold a human head phantom to investigate changes in radiation characteristics when the antenna operates in the presence of a human operator.
High fidelity radiation pattern measurement system for small antennas
P. Kabacik, A. Byndas, R. Hossa, M. Bialkowski
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The paper describes a high fidelity system for measuring a radiation pattern of an electrically small antenna. In this system, the Antenna Under Test (AUT) equipped with a battery powered signal generator is suspended by a dielectric foam in the centre of a pair of dielectric rings that are supported by a pedestal of a spherical positioning mechanical sub-system. Radiation patterns are obtained directly in spherical format using a suitably constructed probe antenna of linear or circular polarization. Measurements are controlled by a computer, which also stores and processes the measured data. The results reveal considerable differences between the radiation patterns of a small antenna obtained using the proposed wireless approach and the conventional one, in which the antenna is connected with a cable to the receiver.
Arbitrary footprint patterns obtained by circular apertures
J.A. Rodriguez, A. Trastoy, F. Ares, E. Moreno
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We describe an improved version of our previously published quasi-analytical method for the synthesis of antenna arrays radiating footprints with shapes that are star-shaped subsets of (?,f)-space.
Application of ant colony optimization based algorithm to solve different electromagnetic problems
O. Quevedo-Teruel, E. Rajo-Iglesias
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The aim of this work is to show the use of a well-known type of evolutionary computation optimization technique, the Ant Colony Optimization (ACO), in order to solve different electromagnetic problems: array synthesis both linear and planar and with different design criteria, design
of a monopolar Ultra Wide Band (UWB) microstrip antenna and reduction of E-plane mutual coupling in a multilayer patch antennas array. To this aim, an algorithm based on the fundamentals of ACO has been developed. The algorithm uses real numbers and binary ones (depending
on the structure to optimize). Some guidelines for the use of the algorithm, especially to create the desirability function, are supplied. The algorithm has demonstrated to be versatile and useful to resolve problems of different nature. Furthermore, the purpose of the work
is to show (via these particular applications) the flexibility and easy implementation of this algorithm family that make it suitable to be used in most of electromagnetic optimization problems.
Beam reconfiguration of linear antenna arrays by using parasitic elements and genetic algorithms
J.A. Rodriguez, G. Franceschetti, F. Ares
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An innovative method for linear arrays beam configuration is presented. In the proposed method, every element of the linear array is connected to its feed through a switch, so it can be active or passive. Pattern reconfigurability is achieved by appropriately switching on or off the array elements. The optimal configuration of the switches for each of the radiated patterns as well the common voltages of the active elements is calculated by using a genetic algorithm. For each configuration, the currents in the driven and parasitic elements are determined, via their self and mutual impedances, by inversion of the impedance matrix. In the presented example, the method has been applied to a linear array of parallel dipoles that switches the power pattern from a pencil to a flat-topped beam.
Transient analysis of microwave antennas by method of moments: feeding ports and efficiency of MOT and MOO methods
J. Lacik, Z. Raida, Z. Lukes
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The paper is focused on the time domain modeling of antennas by the method of moments. For this modeling, a scheme with weighted Laguerre polynomials is used. For efficient using of this scheme, the scaling factor of the time axis and the number of temporal basis functions has to be determined properly. Otherwise, the scheme is inaccurate and time-consuming. In this paper, several clues how those quantities could be chosen are proposed. Further, there is a discussion how to model feeding ports of symmetrical antennas to get a shorter transient response and so an analysis is less time consuming. Using of proposed approaches is shown on an symmetric strip dipole.
A general treatment for the electromagnetic modelling of composite structures with the method of moments
C. Craeye, M. Piette, Th. Gilles
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For more than twenty years, especially since the advent of the well known and extensively used Rao-Wilton- Glisson (RWG) subdomain functions, a lot of accurate electromagnetic modelling with the Method of Moments (MoM) has been accomplished, firstly and mainly for Perfect Electric Conductors (PEC), later also for dielectric bodies. Composite structures made of adjacent homogeneous PEC and dielectric bodies has received
much fewer attention so far [2]. To date, though quite general approaches have been presented [3], no full treatment of this problem has been given yet. The purpose of this paper to make new steps towards such a full treatment. First of all, the PEC bodies are presented along with their dual counterpart, the PMC bodies. Next, both volumic bodies and plates are combined in every possible ways. The concepts of singular edges and
branched bodies are introduced, and the importance of electrical continuity is emphasized. The essential notion of RWG sectors is identified, for which two important properties are demonstrated. The treatment of composite structures is made very general to allow the use the any
testing scheme, coupled to any redundancy reduction scheme. Finally, a new general approach based on the sector property table is proposed where perfect conductors appear as a special case of dielectrics.
Models of multilayer antenna radomes with anisotropic materials
V.N. Peshlov, P.I. Dankov, B Hadjistamov
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A modified Paris’ model [1] for computed-aided radome analysis is presented, which takes into account the dielectric material anisotropy of the radome layers. The analytical model is combined with a practically realized two-resonator method for characterization of the normal and parallel to the surface dielectric parameters of the radome layers. Finally, several examples are given, which illustrate the steps for introduction of appropriate radome models of reinforced and composite radome structures with anisotropy, which accurate represent all the layers formed in the practical radome construction – cores, skins, irregular epoxy glue fillets, protective coatings, etc.
Efficient analysis of cavity backed antennas
F.J. Nunez, I. Stevanovic, J.R. Mosig, A.K. Skrivervik
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The efficient analysis of shielded environments, and more specifically rectangular cavities coupled to radiating elements is treated in this paper. The technique presented uses an MPIE/EFIE formulation for the part located outside of the cavity (antenna for instance), where full 3-D conductors and finite dielectrics embedded in a traditional multilayered structure can be taken into account. Inside the cavity, we use also an
MPIE formulation, where the cavity Green's functions are used.
Comparing two methods to solve the layered sphere problem, application to electromagnetic induction sensors
P. Druyts, C. Craeye, Y. Das, M. Acheroy
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The layered sphere problem can be solved by using a multipole expansion in each layer and imposing the appropriate boundary conditions. This direct approach has some drawbacks because it can be numerically badly conditioned. We show that a tranmission line (TL) formalism can be used to solve the problem and that this approach is better conditioned than the direct approach. The corresponding TL is inhomogeneous because it has a characteristic impedance which varies with the radius and which also depends on the direction. We show how the classical TL expressions can be generalized to take into account such an inhomogeneous TL. Both formalisms are applied to a configuration representative of a metal detector (MD) above a magnetic soil. For such a configuration, a large number of the terms is required in the expansion and the direct approach fails in computing the high order terms because of numerical saturations. In contrast, accurate results are obtained with the TL approach.
Resolution of Maxwell's equations in a non-staggered grid model
P. Pinho, S.M. Gomes, P.J. Ferreira, J. Rocha Pereira, M.O. Domingues, A. Gomide
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In this paper a scheme to obtain an adaptive method in space for the resolution of Maxwell’s equations is presented. Using interpolating wavelets it is possible to obtain an adaptive grid allowing an economy of the computational resources. Using the non staggered grid model the stability factor
is improved when compared with the classic FDTD and its value is greater that one. This factor is more limited with the increase of the interpolating polynomial. On the other hand the dispersion proprieties are more restricted, when compared with a staggered grid model.
Combination of multipole and macro basis function approaches for the analysis of finite arrays with dielectric elements
C. Craeye, Th. Gilles
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Scattering by finite arrays of dielectric elements is analyzed numerically. This is carried out efficiently with the help of a macro basis functions approach. We show how the reduced Method of Moments (MoM) matrix can be computed very fast with the help of multipole decompositions.
The complexity of the method is outlined, and simulation examples are shown for scattering by arrays of dielectric spheres.
Radar cross section of some simple and collected targets to be used for classification
I. Nicolaescu, M. Cernat
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The goal of this paper is to analyze the scattering properties of different kind of targets, from simple shapes to collected targets made up of several objects, from 400 MHz to 7400 MHz to be used as patterns in a Ground Penetrating Radar in the classification stage. The data have been collected in an anechoic chamber with a vector network analyzer (VNA) set to work as a Stepped Frequency Continuous Wave Radar (SFCW).
The data are analyzed in frequency and time domain in order to picture the radar cross section dependency of frequency, incident angle, polarization and target’s shape. The measurement have been carried out using a bistatic arrangement with two TEM horns for linear
polarization and two spiral antennas for circular polarization.
Currents reconstruction with high resolution using the FFT iterative method and spectrum replies
D. Sánchez-Escuderos, M. Baquero-Escudero, E. Alfonso-Alós,F. Vico-Bondía
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The construction of an antenna involves several steps, from its design until the final checking of its operation. This last step is the most critical of them because the manufacturing of an antenna is not as ideal as could be desirable. Errors occur and, sometimes, they are hard to detect so special techniques must be used. One of these techniques obtains the equivalent currents on the surface of the antenna from the measured field. There are many algorithms to make this inverse algorithm, although one of the most used is the spectral technique. The main problem of this technique is its poor resolution. In this paper we propose the combination of two methods, one an iterative algorithm and the other one the use of the periodicity of the spectrum, in order to improve this poor resolution.
Time-domain multi-objective optimization of antennas
Z. Raida, I. Hertl, P. Smid, J. Lacik, Z. Lukes
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A planar dipole antenna is analyzed using time-domain integral equation (TDIE) method. In order to compensate the influence of the shape of the excitation pulse and to suppress dispersion phenomena, an inverse filtering is applied in the time domain using the cyclic convolution. In order to keep computations in the time domain, an objective function is formulated in terms of time-domain parameters. A global optimum is sought by genetic algorithms and particle swarm optimization. The antenna is required to exhibit the maximum bandwidth, the maximum gain, and the minimum dimensions at the same time. Since these objectives are conflicting, a multi-objective approach is applied, and the set of Pareto optimum solutions is computed.
Enhanced neural modeling of planar antennas and filters
P. Smid, Z. Raida, J. Horak
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The paper deals with an enhanced neural modeling algorithm based on incorporation of both, global optimization method and local one. Proposed algorithm depresses disadvantages of classical neural modeling. A neural model of the low-pass filter is trained to behave as a numerical one, which is analyzed in Zeland IE3D. Both, the neural model and the numerical one are optimized using particle swarm optimization method (PSO). Finally, the results of optimization are compared.
Designing reverberation chambers for measurements of small antennas and wireless terminals: accuracy, frequency resolution, lowest frequency of operation, loading and shielding of chamber
P.-S. Kildal, C. Orlenius, J. Carlsson, U. Carlberg, K. Karlsson, M. Franzén
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The last five years the reverberation chamber has been developed to an accurate instrument for measuring the performance of small antennas and active mobile terminals in Rayleigh fading. The present paper gives an overview of the research done by the authors in relation to achieving an accuracy of 0.5 dB RMS or better, when measuring efficiency and radiated power. The accuracy has been verified by comparison with
measurements in anechoic chambers, and between reverberation chambers of different size, and from participation in benchmarking of measurement ranges done within ACE (Antenna Center of Excellence, a European Network of Excellence). There have also been developed procedures for measuring quantities that are specific for the Rayleigh environment, such as diversity gain, MIMO capacity, and static as well as
dynamic receiver sensitivity at certain data error rate (BER or FER). The paper will describe important topics related to the mode stirring and loading of the chamber, such as the accuracy, frequency resolution, average transfer function, and the system bandwidth when measuring active terminals. Numerical simulations play an important role in controlling the chamber performance.
Amplitude-only measurement technique on strategic near-field scanning surfaces
S. Costanzo, G. Di Massa
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The problem of near-field phase retrieval from amplitudeonly measurements is faced in this work. A novel hybrid approach is proposed which obtains phaseless information by two co-planar probes simultaneously scanning a single near-field surface. An interferometric procedure is then adopted in conjunction to a minimization technique for retrieving the unknown near-field phase. The proposed approach is experimentally validated on a cylindrical scanning surface with a X-band pyramidal horn used as test antenna. The phase retrieval procedure is also applied to the helicoidal scanning geometry and an efficient far-field transformation directly applied to near-field helicoidal data is developed and numerically validated.
Ultra wideband antenna of two bow-tie monopoles
M. Knezevic, T. Debogovic, J. Bartolic
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In this paper novel ultra wideband (UWB) antenna designs suitable for ceiling-mount base station and small terminal applications are presented. Two different designs of antenna arrays employing two triangular radiators above a ground plane have been investigated. In the first design, triangular unipoles are settled parallel one to each other at the distance of a half wavelength at the 3 GHz. In the second design the same radiators are tilted to form a conical like structure. The in-phase excitation of the unipoles was performed by a section of the microstrip line which is centrally fed by a coaxial probe from the opposite side of the ground plane. The input impedance and radiation patterns of both antennas are simulated and measured. In the frequency range 0.8– 5 GHz the VSWR was less than 2. have shown mobile base station and small terminal applications.
Design guidelines for the UWB pyramid antenna
S. Bruni, A. Neto, F. Marliani
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In this paper a novel UWB directive and non dispersive lens antenna is presented. It is based on the broad band leaky wave radiation occurring at a slot printed between different homogeneous dielectrics. This paper presents the guidelines for the UWB design, the hardware demonstrator and pertinent measurements. The main motivation for this work was the development of a field sensor for electromagnetic compatibility to be used in the range 4-40 GHz.
Double ridged structures mode study for broadband antennas design
Z. Hradecky, M. Mazanek, T. Korinek
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Knowledge of the cutoff frequencies of modes in nonstandard double ridged waveguides is extremely important for determination of operation bandwidth for design of broadband structures. It is shown that for nonstandard dimensions of the ridged waveguide the TE30 mode doesn’t exist or is degenerated or the higher mode skips the TE30 mode. Strategy of the complex broadband double ridged horn antennas design (coaxial
– waveguide transitions, impedance transformers, radiated ridged and horn structures etc.) is mentioned and as an example the 4-40GHz antenna is presented.
Ultra wideband spiral antenna - time delay removal
I. Nicolaescu, P. Van Genderen
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This paper deals with the time delay removal of an Archimedean spiral antenna which operates from 400 MHz to 4845 MHz. As it is known, spiral antennas show a dispersive behavior, thus, in time domain, a “chirp” pulse will be displayed at the output. For time delay removal two procedures are investigated: the first one uses an error-term flow graph for the frequency signal as for Vector Network Analyzers while the second one supposes to place a reference metallic plate at a certain distance in order to identify the phase dispersion given by the antenna. In the second case the received signal is passed in time domain by applying an ifft, the multiple reflection are removed and the phase variation due to the time propagation is subtracted. After phase correction the time domain response as well as the side lobes level are decreased. The antenna system made up of two Archimedean spirals is employed by a stepped frequency continuous wave radar (SFCW) which works with a frequency step of 35
MHz.
Shaped single-feed-per-beam multibeam reflector antenna
P. Balling, C. Mangenot, A.G. Roederer
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Current Ka-band multibeam satellite antenna systems often use one feed per beam, but involve a high number of reflector antennas (four for transmit and four for receive) to realise both acceptable crossover levels and spillover losses [1]. Several developments go on to reduce the number of reflectors to one for transmit and one for receive at the cost of much complexity in the feed array and beamforming. Orthogonal efforts aim at developing antennas that both receive and transmit. Here we present a new concept (patent pending) where a shaped reflector reduces both the number of feeds per beam and the number of reflectors to one (with separate receive and transmit antennas). The price paid is an oversizing of the reflector making the reflector area comparable to the total area of the conventional four-reflector solution.
Non-effective medium composite right/left handed transmission lines - design and applications
J. Perruisseau-Carrier, A.K. Skrivervik
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We present a method to design composite right/left handed transmission lines (CRLH-TLs) that exhibit a continuous phase shift around a given frequency of 0° degree phase shift and optimal matching within a large bandwidth. The developments are based on a Bloch wave formulation on general CRLH-TL unit cell circuits. The design method is exact based on these circuits and is therefore valid both for effective or noneffective
medium CRLH-TLs, which are shown to be also relevant realizations of CRLH-TLs. In particular, the benefits of the method are demonstrated in the case of different applications such as integrated phase shifters, leaky-wave antennas and low-impedance transmission lines.
Application of composite right/left handed transmission lines to antenna matching
A. Diaz Bolado, F. Bongard, J. Perruisseau-Carrier, J.R. Mosig
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This work concerns the application of Composite Right/Left-Handed Transmission Lines (CRLH TL) to antenna matching. First, general considerations are made regarding the advantages and limitations of realizing quarter-wavelength transformers (QWT) using CRLH TL instead of usual transmission line sections. In order to implement CRLH TL-based QWT (meta-QWT), a method to design CRLH TL sections with a given non-zero phase shift and impedance at the required frequency was developed. The method was then applied to the design of multisectional
QWT for the matching of CPW-fed slot loop antennas both in a printed technology with surface-mount technology (SMT) elements and in a fully integrated micromachining approach. It is shown that the use of CRLH TL can lead to some significant size reduction and bandwidth enhancement, but that the improvement is strongly dependent on the technology and frequency considered.
Characterization of metamaterial slabs in terms of scattering parameters under oblique plane wave incidence
F. Bongard, I. Stevanovic, O.J.F. Martin, J.R. Mosig
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In this work, a retrieval procedure which allows the determination of equivalent dyadic permittivity and permeability of metamaterials from reflection and transmission coefficients obtained for several incidence directions and polarizations is presented. The main goal is to determine to which extent a model of anisotropic homogeneous material can be applied to specific metamaterials. Preliminary results on wire media and arrays of magnetic resonators show that a certain level of symmetry in the unit cell is required to avoid bianisotropy, and that small unit cells compared to the wavelength are favorable for such a homogenization.
Comparison of bandgaps and bandwidths of mushroom-type EBG surface and strip-type soft surfaces when used as narrow ground planes
E. Rajo-Iglesias, L. Inclán-Sánchez, P.-S. Kildal
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The purpose of this work is to compare different striptype soft surfaces and mushroom-type EBG in different aspects. Firstly, strip-type soft surfaces are characterized in the same way as electromagnetic bandgap (EBG) surfaces, i.e. in terms of dispersion diagrams and bandgaps.
Secondly, they are also studied in terms of the bandwidth of a system related performance parameter; when they are used as narrow ground planes to reduce back radiation. To this aim a vertical electrical source is used. The results are in both cases compared with those of mushroom-type EBG surface. The strip loaded soft surface can be realized with periodic via holes (like in patch-type EBGs), in this case the via period is used as an extra parameter to optimize the bandgap. Also, the placement of the vias either in the centre or at the edge of the strip, both
for strips and for mushroom-type EBGs has been investigated. The lateral position moves the bandgap to lower frequencies, thus giving smaller period of the surface for a given frequency. When the surfaces are used as small (1.5?) ground planes both, strips and mushroom have similar performances for TM case (vertical polarization) whereas the strip surface has larger bandwidth for TE case (horizontal polarization).
Parameter identification of an equivalent circuit model via support vector regression for frequency selective surfaces
L. Fernandez-Martinez, E. de Lera-Acedo, E. García-Muñoz, A. Navia-Vazquez, D. Segovia-Vargas
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A method for the analysis and design of Frequency Selective Surfaces (FSS) based on Support Vector Regression machines is developed. FSS representation with an equivalent circuit composed of lumped elements is very useful in the design stage of systems, where it is desirable to know in a quick way if a FSS is able to give a fixed frequency response. A high number of equivalent circuit elements are necessary in order to
build the design model. The way to obtain these elements is often performed by an analysis procedure based on time -cost full-wave simulations.
The use of Support Vector Regression machines speeds up this procedure, making easier the analysis step. These machines are likely to bring good results also in the design step, instead of the complex equations typically used. The method will be validated with a periodic structure of metallic ring resonators on a dielectric substrate.
Reconfigurable slot antennas with fixed-fixed beam and cantilever type RF MEMS capacitors
E. Erdil, K. Topalli, M. Unlu, I. Istanbullnoglu, E.U. Temocin, H.I. Atasoy, O. Bayraktar, Ö. Aydin Civi, S. Demir
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Design of a 1-metre reflectarray for DBS application with 15% bandwidth
J.A. Encinar, M. Arrebola, M. Dejus, C. Jouve
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A one-meter reflectarray has been designed for a DBS European coverage in a 15% frequency band (10.95- 12.75 GHz). The reflectarray is made of three stacked layers of printed arrays with rectangular patches. The dimensions of the staked patches are optimised in each element to ensure the required coverage at five frequencies in the working band. The radiation patterns fulfil the contour requirements for both H- and Vpolarisation
in the required frequency band.
Suitable planar transmit-array in X-band
M. Barba, E. Carrasco, J.A. Encinar
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This paper presents two planar transmit-array configurations with one ground plane. The requirements of the radiating elements are discussed and the design of two patch based radiating elements, which are considered suitable for a X-Band Transmit-Array, is presented. The measurements of the manufactured prototypes are included.
Advances in reflectarray bandwidth enlargement
G. Di Massa, S. Costanzo, F. Venneri
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An aperture coupled reflectarray element, with smooth and linear phase variations, is proposed for bandwidth enhancement by exploiting the spacing between adjacent elements in the array grid. The comparison of phase curves computed at various frequencies for some test cases is used to prove reflectarray bandwidth enlargement. As further validation, radiation pattern measurements have been performed to compare
bandwidth features of two 20 GHz reflectarray prototypes with different cell size.
Design of planar antennas for GALILEO using EBG structures
R. Baggen, M. Martínez-Vázquez, J. Leiss, S. Holzwarth
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The design presented in this paper is a dedicated antenna for geodetic applications using the future GALILEO system. It is characterised by an ultra-low multi-path behaviour resulting in a very stable phase centre. In the past, choke ring structures have been used to obtain this effect, yet they are heavy and bulky. The antenna presented here uses instead Electronic Band Gap technology. The resulting printed structures are low-weight, low-cost and low-profile, which results into a very compact and commercially interesting antenna module with good performance.
Tolerance analysis of S-band inflatable antenna arrays
P. Kabacik, M. Preisner
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The paper is concentrated on tolerance analysis required to develop antennas made with pressurized structures. Inflatable antennas are desired for many applications emerging in modern mobile, rescue and satellite communications and in some portable radar.
Lightweight conformal dual band antenna for spaceborne applications
P. Kabacik, G. Jaworski, M. Kamaszuk, P. Hornik, T. Maleszka
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The paper presents a dual-band integrated antenna for use onboard spacecraft. The L- and S-band antenna was developed in a course of our research we have carried on spacecraft antennas. The designed antenna features low profile which is more and more often desired in modern spacecraft. However, when antennas have low profile it is extremely difficult to generate high quality circular polarization over the wide spatial angle across the beam of the antenna element. The design of antenna electromagnetic and microwave circuits are meeting this expectation, so one patch is capable to serve well communication subsystem in one band across the entire radio horizon seen from the International Space Station (about 4000 km in diameter). Owing to conformality in the profile the antenna can be mounted on Earth and save significant efforts during attachment of the module.
Onto optimization of TTC patch antennas placed on minispacecraft
P. Kabacik, P. Opalka, T. Maleszka, P. Gorski
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This paper presents the approach to optimal TTC patch antennas placement onboard minispacrafts. The construction of the antennas is briefly discussed and chosen schemes of antennas placement are introduced. Influence of solar panels is also investigated and countermeasures against failure of their deployment are proposed. The results of the analysis were obtained with the use of Moment Method simulations and measurements. Alternative, computationally more efficient ray-tracing method is mentioned and compared with full-wave simulations.
On the optimal dimensions of helical antenna with truncated-cone reflector
D.I. Olcan, A.G. Zajic, M.M. Ilic, A.R. Djordjevic
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This paper presents optimization of a helical antenna with a truncated-cone reflector. We have found that the dimensions of the truncated-cone reflector and the dimensions of the helical antenna need to be optimized simultaneously to obtain the optimal design. Furthermore, we have found that the truncated-cone reflector can significantly increase the gain of the helical antenna compared to a circular or a square flat reflector. A set of diagrams is made to enable simple design of helical antennas with truncated-cone reflectors. Finally, the results are experimentally verified.
Coupling among collocated loops
M.M. Nikolic, A.R. Djordjevic, A. Nehorai
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We analyze three orthogonal collocated loops using semi-analytical and numerical procedures. If a large number of terms is used, the currents in the loops converge to those of galvanically interconnected loops. The three loops are sensitive to positioning tolerances so that large coupling among them can occur in practice.
Planar monopulse antenna with radial line feeding at 37 GHz
P. Rodríguez Fernández, J.L. Masa Campos, S. Guillot Durán, M. Sierra Pérez
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A new feeding structure based on parallel plates radial line applied on planar arrays is shown in this paper. When a high gain antenna for a high frequency system is being designed, low losses feeding networks must be taken into account [1]. Typically waveguide feeding networks are being used in this kind of applications. In order to show how parallel plate [2][3] feeding networks works a planar array antenna working at 37 GHz frequency is presented. The system requires right hand side polarization (RHCP) with axial ratio under 3dB and modified circular patches are used as radiating element. To couple the power from the parallel plates guide to the radiating elements, properly designed microstrip coupling lines have be used.
Low-cost dual polarized feed for high resolution SAR reflector antennas
M. Viberg, P. Koch, J. Guijarro, K. van't Klooster
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SAR antennas on satellites are usually large arrays. Missions like Envisat and TerraSAR-X use active phased arrays with great flexibility and wide swath coverage. Despite the tremendous flexibility involved, such active array systems are however complex, bulky, heavy and hence fairly expensive. At the other end of the scale there is the single beam reflector antenna. The obvious advantages with these systems are the low
weight, the potentially large bandwidth and low cost. A SAR system based on a reflector antenna can thus provide high resolution at low cost and - opposed to active systems - at the expense of flexibility and swath coverage. However, this paper describes a feed system for a reflector antenna that will give two sets of multiple dual polarized beams (each set having prescribed beam characteristics), combining some of the flexibility and wide swath coverage of the phased array with the low cost and weight of the reflector system.
Optimization of prime-focus circular waveguide feed with septum polarization transformer for 1.296 GHz EME station
P. Hazdra, R. Galuscak, M. Mazanek
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We describe the reduction of polarization losses and other optimizations in the design of a septum polarizer antenna feed configured in a circular waveguide. The goal is to improve the overall efficiency of a parabolic dish antenna system which will be used for EME (Earth-Moon-Earth) microwave communication.
Leaky wave enhanced feeds to increase the edge of coverage gain in multi-beam reflector antennas
N. Llombart, A. Neto, G. Gerini, M. Bonnedal, P. de Maagt
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Present and next generation telecommunication satellite systems often require multiple beam capability. The three fundamental ways to achieve high coverage gain are overlapping feed arrays, with complicated feed networks, interleaved beams, with multiple apertures, and designs with a single aperture and a single feed per beam. This last approach typically requires small aperture feeds in order to obtain a small beam separation, however these small feeds have low gain which results in 2 or 3 dB of power lost in spill over from the reflector.
Simulated response of conic Fresnel zone plate reflectors (CFZPs)
J. Gutierrez-Rios, J. Vassal'lo
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Planar Fresnel Zone Plates (FZP) substitute the curved surfaces of a Fresnel Reflector for an stepped one, getting advantages concerning to manufacturing and prize. Besides, this technology provides the possibility of designing conformed beam antennas, as for example when a double beam is required. The main disadvantage of FZP is the inherent loss in gain of the stepped approximation, though, as we have been able to prove,
efficiency results to be very reasonable and equilibrated with the other advantages for many uses. Conic Fresnel Zone Plates (CFZP) consist of FZPs developed over a conic surface instead of a planar one. This change provides more efficiency preserving the advantages of FZPs without a noticeable increase in size or occupancy. The synthesis procedure of CFZPs drives to a new conception of reflector that we have called Fresnel Flat Zone Cone (FFZC) whose structure is very simple in comparison with FZPs and CFZPs, while the degree of approximation and, then, the performance is much better. A procedure for optimal synthesis of FFZCs is also presented.
Multimode hard horn antennas with partly corrugated walls for 20/30 GHz dual-reflector antennas with multiple beams - full 3D simulations and measurements
O. Sotoudeh, P.-S. Kildal, P. Ingvarson, S. Skobelev
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We introduce a partly corrugated hard horn, consisting of a smooth-walled horn with an attached longitudinally corrugated outer section. This is used and controlled to design better and shorter single-band horns than otherwise possible. Furthermore, it enables the design of dual-band horns with low crosspolarization and high gain, for multi function use at Ka-band with transmit and receive frequencies in the same antenna. A model of such a dual-band horn was manufactured at Saab Ericsson Space and measured. The design was done by using efficient in-house mode matching code based on homogenized asymptotic boundary conditions for the corrugations. This has been verified by heavy computations using a 3-D
FDTD code. The measured laboratory model had too large cross polar sidelobes, but the later extensive computations showed that these sidelobes would have been in agreement with the mode matching results if the number of corrugations was doubled.
Two-dimensional interpolation for the numerical estimation of the mutual coupling in large antenna arrays
M. Joghee Mehta, C.I. Coman, I.E. Lager
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A strategy to account for the effect of the mutual coupling in the case of the synthesis and the analysis of nonperiodic array antennas is discussed. It relies on a twodimensional interpolation of a reduced number of coupling admittances that can be evaluated by either computational
techniques or direct measurements. In view of its efficiency and robustness, the method is amenable to being included in design and optimisation procedures concerning large, non-periodic radiating structures.
Thermoregulatory response to electromagnetic plane-wave exposure at 900 MHz
M.A. García-Fernández, J. Valenzuela-Valdés, M.A. Martínez-González, D. Sánchez-Hernández
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In electromagnetic dosimetry the mobile phone antenna scenario is the typical problem and consequently farfield exposure has received less attention. International safety limits provide reference levels expressed in terms of EM field strengths, which are evaluated in the absence of a person and derived from plane-wave incidence and CW exposure, which is limited to farfield situations. The rationale for deriving basic restrictions and their associates safety margins is not fully standardized and diverse values are employed depending upon the thermal effect being considered. In this contribution, more realistic exposure scenarios and response effects are evaluated, including a 10W/cm2 plane-wave incident exposure. SAR is provided for all tissues, and the hybridization between EM field exposure and thermoregulatory response has provided interesting results, such as the additional thermal safety factor that the skull represents for the human body under EM field exposure. The described model could be
useful for surgery operations like DBS, etc.
ACE 2 activities on small terminal technologies and applications
M. Martínez-Vázquez
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This paper presents the work carried out in the ACE Network of Excellence regarding technologies for small terminal antennas. The aim is to identify the newest trends in antenna design for personal communications devices, and suggest novel solutions and design methodologies for various applications.
Optimal antenna placement for mobile terminals using characteristic mode analysis
J. Rahola, J. Ollikainen
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When an electrically small antenna element is placed on a small finite ground plane, as in mobile terminals, the ground plane resonances strongly affect the impedance and radiation characteristics of the antenna system. In this paper, we show how characteristic mode analysis can predict the optimal locations of antennas on finite ground planes. As patch-type antennas couple to the ground plane resonances mainly through the electric field, it is natural that the strongest coupling and thus the maximum impedance bandwidth is obtained when the antenna element is placed at the maximum of the electric field of a ground plane mode. This is verified by moving a small probe antenna at selected locations over a rectangular 100
mm by 40 mm ground plane and by computing the obtainable bandwidth at each point.
Results and experiences from two years of benchmarking of measurements facilities for small antennas and terminals within ACE
J. Carlsson
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This paper presents the test cases defined in ACE (European Antenna Centre of Excellence) for benchmarking of facilities for measuring small mobile terminals and antennas, as well as results and experiences of the round robin test. The emphasis is put on measurements in the most popular communication frequency bands. Several test cases for passive antennas as well as for active devices were defined and collected in a test kit that was sent to different test facilities around Europe in a round robin test. The measured parameters include radiation efficiency, total radiated power, diversity gain and receiver sensitivity. The test cases include different locations of the test devices relative to a lossy cylinder that has dielectric characteristics resembling that of a human head.
Mobile terminal antenna implemented by using direct coupling
J. Holopainen, J. Villanen, C. Icheln, P. Vainikainen
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The current trend in mobile terminals is an increasing number of systems. The volume occupied by the antennas of the radio systems is becoming more and more problematic and new low-volume antenna solutions are needed. Since the EMC shielding and the ground plane operate as the main radiating structure especially below 1 GHz, a very small antenna structure can be achieved by using a direct feed, i.e. galvanically inducing currents on the surface of the chassis. The feed can be placed over an impedance discontinuity, e.g. formed by a slot. Using this approach, an antenna structure for a small handheld digital television (DVBH) receiver is presented. The antenna gain exceeds the specification by a 4-dB margin. The introduced antenna structure can also be used for multi-system terminals.
Multiband patch antennas with edge perturbation elements optimized by genetic algorithm
M. Polivka, P. Hazdra, M. Drahovzal
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A multibandband patch antenna design based on the Genetic Algorithm (GA} control of the pseudorandom generation of the patch topology in a grid of conductive cells is presented. GA operates on subdomains of the basic grid forming an original rectangular patch and creates meander edge notches to modify the radiator for excitation of higher order modes with the required radiation properties. Matlab/IE3D software environment has been used for the design of optimization loop. Results of 2.4/5.8 GHz dualband patch antenna design are presented. The principle of the multiband behavior is further explained via a description of vector surface current distribution of operational modes.
Improving radiation pattern of microstrip antennas
M.M. Nikolic, A.R. Djordjevic
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It was shown in [1] that polarization currents in the dielectric substrate of microstrip antennas cause deterioration of the radiation pattern. We further study this effect analytically and numerically, with emphasis on techniques for improving the radiation pattern.
Reverberation chamber evaluation of multi-antenna handsets having low mutual coupling and high efficiencies
A. Diallo, C. Luxey, P. Le Thuc, R. Staraj, M. Franzén, P.-S. Kildal
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This paper presents the evaluation of the diversity performances of several multi-antenna structures in a reverberation chamber. Firstly, a two-antenna system having low isolation between the radiators is measured. Its performances are compared with a second structure which uses a neutralization technique to enhance the radiating element’s isolation. Then the performances of a four-antenna system with and without the neutralization method are measured and presented. Particularly, the total antenna efficiencies, the envelope correlation coefficients and the diversity gain of these systems are presented and discussed. We especially focus on the advantages of the neutralization technique.
Circularly polarized slot antenna with toroidal coverage
J. Bäck, J. Zackrisson
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Saab Ericsson Space has a long tradition in developing wide coverage antennas for satellites, see also [3] and [5]. We have recently developed a K/Ka-band antenna family. These antennas are used for satellite applications such as telemetry, command and beacon functions. This paper will describe the design and development and also present performance of one of the members, a dual mode biconical type antenna with circular polarization, toroidal coverage and a redundant waveguide feeding.
Evaluation of diversity and MIMO performance of antenna from phaseless radiation patterns
J. Krogerus, P. Suvikunnas, C. Icheln, P. Vainikainen
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We investigate the significance of phase information of radiation patterns for the performance estimates of diversity and multiple-input-multiple-output (MIMO) antenna configurations at 2 GHz band. We also propose a random-phasing technique for performance analysis when the phase information is not available. In the performance analysis we use the Experimental Plane- Wave Based Method (EPWBM) where 3-D radiation patterns of the antennas and measured 3-D signal distribution of the propagation environment are combined. The results show that use of phaseless radiation patterns leads to unacceptable underestimation of performance of multielement antenna systems. However, the use of a random phasing technique with phaseless radiation patterns is shown to be an attractive method for simplifying the antenna evaluation process.
User effect on total radiated power and 3-D radiation pattern of mobile handsets
J. Krogerus, J. Toivanen, C. Icheln, P. Vainikainen
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We investigate how the user’s body affects the radiation characteristics, i.e., 3-D radiation pattern and total radiated power (TRP) of mobile handsets. In previous studies up to 10 dB difference was found in TRP of a mobile handset between individual users. Our objective is to investigate the reasons for the large differences. Thirteen test persons were measured with an active GSM 900/1800 mobile phone. The standard deviation of the TRP results between the test persons was relatively low when the test persons held the phone in a predefined talk position. The variation in the corresponding results was much larger when the users could freely select the talk position. The variable hand position and the grip on the handset seems to be the major reason for the large differences whereas the anatomical differences between the users play only a smaller role.
Performance of MIMO systems with multiple multimode compact patch antennas
E. Rajo-Iglesias, Ó. Quevedo-Teruel, M.L. Pablo-Gonz´lez, M Sánchez-Fernández
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The purpose of this work is to study the performance of Multiple-Input Multiple-Output (MIMO) systems that use multi-mode antenna as basic elements. The design is focused to be a compact model, suitable for being used in relatively small terminals. Given the small size of the designs,
the idea is not to substitute the use multiple antennas for one element with multiple modes but to combine multiple compact multi-mode antennas. To this aim, the design of two small multi-mode patch antennas is presented as well as a study of channel spectral efficiency. Spectral efficiency is computed comparing several multielement- multimode antennas scenarios to alternative scenarios with single-mode antennas. For spectral efficiency studies it is necessary to model the MIMO channel taking into account that multiple-element-multiple-mode antennas will be used. The proposed model relies on a small set of parameters that fully characterizes spatial and modal correlation in terms of the antenna geometry, the radiation patterns and the angular spread in the channel.
Effect of smart antennas on CDMA uplink and cross-border mitigation
I. Simöes, I. Stevanovic, A.K. Skrivervik
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Zero-thickness wideband antennas for small radio transceivers
P. Kabacik, A. Byndas, R. Hossa, M. Bialkowski
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The paper presents investigations into compact zero-thickness wideband antennas capable of operating in many frequency bands within 800-3000MHz. Multi-band operation of these antennas is accomplished by suitable meandering of conducting segments that may be supported by a thin dielectric film. The antennas are capable of operating with a very small ground plane formed by an adjacent conducting surface or a feeding transmission line. Because of the use of flexible materials, these antennas can be conformed to planar or cylindrical structures. Their operation is tested experimentally in stand-alone configurations as well as in the presence of enclosures.
A model for the radiation resistance of a bent planar monopole antenna
L. Aberbour, C. Craeye
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In order to achieve a convenient small antenna size, often a monopole antenna is printed on a substrate sheet and bent into the shape of a so-called inverted L or inverted F antenna. In this paper we consider the perfectly electrical conducting half-sheet configuration, which is a
special case of a wedge, to derive an analytical representation for the radiation resistance of a miniaturized planar bent folded monopole antenna. This model is validated by simulations and compared to the case of a standard short monopole. Its higher radiation resistance than that of the conventional short monopole is put forward in this paper, which is due to its linear dependance on the antenna height.
Miniature microstrip fractal patch antenna working with crossed-diagonal
P. Hazdra, M. Mazanek
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Paper describes a novel type of miniature microstrip patch antenna based on fractal geometry. Miniature properties are achieved by the presence of unusual fundamental resonant mode which we call “crossed-diagonal” (CD) current.
A survey of small antennas design at the LEAT
C. Luxey, R. Staraj, G. Kossiavas, A. Papiernik
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Numerous small antennas have been designed at the Electronics, Antennas and Telecommunication Laboratory (LEAT) of the University of Nice Sophia-Antipolis. In this paper, we perform a detailed analysis of the best concepts. We especially focus on the different miniaturization techniques employed to reduce the size of these structures.
8x8 element digital beam forming antenna array for Ka-band
S. Holzwarth, O. Litschke
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LTCC multilayer modules are appreciated for their flexibility in realising an arbitrary number of layers with easy-to-integrate circuit components like via-holes, cavities, thick film resistors, SMT components and chip devices. For the frequency range of Ka-Band, manufacturing tolerances become however more critical with respect to the wavelength. Yet, the demand for high integration is especially increasing for this frequency range. For example, the increasing demand for mobile access to fast data services is one of the drivers for future broadband satellite systems in Ka-Band. Steerable antennas employing Digital Beam-Forming (DBF) provide fast and flexible reconfiguration capabilities required for such systems without any moving parts. The antenna presented in this paper is a circularly polarised, 8×8 element array, consisting of four 4×4 element building blocks. The array can be used for a digital beam forming terminal (transmit system) operating from 29.5 GHz to 30.0 GHz. In this paper, the EM modeling of the complete 4×4 array building block, including its feeding and calibration network, are presented. Thereafter, probe measurements and far field measurements on the building block prototypes are discussed. Subsequently, the far field behavior of an 8×8 antenna array is analyzed.
Electronically switchable multi-polarisation circular patch antenna for conformal arrays
T. Debogovic, S. Skokic, J. Bartolic
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A novel reconfigurable antenna structure allowing polarization rotation is proposed. The antenna is a linearly polarized aperture coupled circular patch antenna, with three independent radial feeding lines allowing to rotate the polarization in steps of sixty degrees. The desired polarization sense is achieved by turning on the PIN diode at the beginning of the appropriate feeding line. Measured results show good matching and low cross-polarization levels, and agree well with the theory. The proposed architecture can be advantageous for use in doubly curved antenna arrays, where the possibility to align element polarizations directly translates into an increased array gain.
Miniaturized circular patch antenna with metamaterial loading
F. Bilotti, A. Alù, N. Engheta, L. Vegni
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In this contribution, we present a possible implementation of a miniaturized circular patch antenna with metamaterial loading. In previous theoretical investigations we have already shown that it is possible to excite a resonant radiating mode in a circular patch by using an inhomogeneous substrate made of the combination of a regular dielectric and a metamaterial exhibiting a negative real part of the permeability. While in our previous works we have considered the metamaterial as an ideal isotropic material described by a Lorentz-like dispersion, here we propose a possible implementation of the same structure, employing proper resonant inclusions. A theoretical cavity-model analysis allows determining qualitatively the expected near field distribution of the antenna at its resonance and therefore optimizing the location and orientation of the inclusions. The final layout has been simulated through a full-wave commercial code and the resulting matching and radiation features, in good agreement with our previous theoretical investigations, demonstrate the possibility of realizing a resonant sub-wavelength patch exhibiting good matching and radiating features.
Development of three models of the Eleven antenna: A new decade bandwidth high performance feed for reflectors
P.-S. Kildal, R. Olsson
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The Eleven antenna is a novel dual polarized ultra wide band (UWB) feed with a decade bandwidth for use in both single and dual reflector antennas. The special name is associated with its basic 11 ? configuration of two parallel dipoles with 0.5 wavelengths spacing, and because it can be used over more than a decade bandwidth (and 11 > 10 ?) with 11 dBi ? directivity by making the dipoles logperiodic. The phase center has a constant location in the ground plane, so a high aperture efficiency of the reflector of 66% or better is available over the whole band. The return loss is better than 5 dB, but we believe that it is possible to achieve 11 dB ?. The feed has no balun as it is intended to be used with an active
180 deg balun and receiver. The Eleven antenna is about 11 times smaller ? than alternative end-fire logperiodic feeds.
EBG enhanced feed for high aperture efficiency reflector antennas
A. Neto, N. Llombart, G. Gerini, M. Bonnedal, P. de Maagt
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Reflector antenna systems have been thoroughly investigated for decades and represent a mature technology. Major improvements in their performances cannot be realistically expected. Typically the feeds of the reflectors are realized with high performance corrugated horns that can be optimized for high efficiency, high gain, low cross polarization, high or low focal to diameter (F/D) ratio etc..
Control of reflection and mutual coupling losses in maximizing efficiency of dense focal plane arrays
M.V. Ivashina, M. Ng Mou Kehn, P.-S. Kildal, R. Maaskant
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The FOV of a radio telescope fed by a cluster of conventional horns in a one-horn-per-beam configuration is limited to a few beamwidths due to the field distortions which appear for off-axis directions of observation. To overcome this limitation, it has been suggested to use dense Focal Plane Arrays (FPAs) of electrically small elements in which several of these elements contribute to each beam. The primary goal of the paper is to investigate the impact of reflection, coupling and dissipation losses in dense FPAs on the total aperture efficiency of the re- flector antenna. We present and discuss results obtained for two dense array realizations: one reference realization of miniaturized open-ended hard waveguides, and
another practical FPA of Vivaldi elements.
TTC patch antennas made in a conformal form with small radius
P. Kabacik, P. Opalka, P. Hornik
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Telemetry, Teleranging and Telecommand (TTC) communication is essential to maintain space missions. Antennas for TTC applications must feature wide – or even omnidirectional – radiation properties. In this paper we present results of our investigations on small size cylindrical arrays which can ensure such radiation properties. Due to small volume required they can be mounted at top and bottom of small spacecraft. Our interest is focused on the S-band, however, results can be extended onto upper microwave frequency bands. We attempted to optimize radiation and impedance properties of patch elements conformal to a small radius cylindrical surface, which is about a wavelength in diameter. The considered cylindrical arrays consist of three to seven probe-fed patches. As a further upgrade to the investigated cylindrical antenna we propose to use a spherical patch on a top of such cylindrical arrays. With use of less expensive materials, the proposed antenna concepts can be applied in wireless communication and in electronic instruments.
Multi-polarized high-gain omni directional arrays
N. Herscovici, Z. Sipus
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In recent years, the need for high gain omnidirectional antennas increased considerably. The antennas are used in a variety of bands anywhere from VHF to millimeter waves bands, in different configurations which mainly differ in gain. The omnidirectionality is mostly obtained using back-to-back elements or simply using dipoles in different collinear-array configurations. The antenna proposed in this paper is an array of cylindrical patches which generates an omnidirectional pattern in the azimuthal plane. The polarization can be either linear or circular.
Design of a triple patch antenna element for double curved conformal antenna arrays
P. Knott
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The number of antenna elements on a planar or curved antenna aperture required for high directivity and twodimensional beam steering can easily become very large, especially if an element spacing around half the free space wave length is required. The present paper describes the design of an antenna sub-array carrying 3 circularly polarized patch antennas at a centre frequency of f = 9.5 GHz and a phase corrected feed network on a common substrate. The sub-array is suited for easy integration into antenna arrays with double curved aperture and can be seen as a trade-off between antenna gain vs. beam granularity. The application of the triple patch antenna to the development of a spherical antenna array with 95 subarrays, a diameter of 300 mm and an opening angle of 112° is also shown. Experimental results on antenna matching and radiated far field patterns as well as numerical beam forming results are presented.
Hybrid spectral domain - UTD method applied to conformal antenna analysis
M. Bosiljevac, P. Persson, Z. Sipus
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A hybrid spectral domain – UTD method (Uniform Theory of Diffraction) developed for the analysis of conformal antennas is presented in this paper. The basic idea behind the hybrid method is to combine different analysis methods for conformal antennas and, at the same time, preserve the advantages of the considered methods. More specifically, the considered hybrid SD – UTD method joins the possibility of analyzing multilayer structures (spectral domain method) and the possibility of analyzing electrically large structures (UTD method). Hence, using the developed method it is possible to analyze large multilayered conformal antennas with high accuracy and speed. This work has been made possible by the ACE program for structuring the research on conformal antennas in Europe. The developed method is a result of joining research activities of University of Zagreb, Croatia and the Royal Institute of Technology, Sweden.
Optimal design of switched beam antenna arrays using Particle Swarm Optimization
K.A. Papadopoulos, C.A. Papagianni, I.E. Foukarakis, D.I. Kaklamani, I.S. Venieris
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Adaptive antennas techniques are emerging as a promising solution to a number of problems in applications related to mobile communications. This
paper presents a method for optimal design of switched beam planar antenna arrays based on the particle swarm optimization (PSO) algorithm. Switched beam antenna arrays are a subset of smart antennas that that can enhance the capacity of a cellular system. PSO is a population based algorithm that exploits a set of potential solutions to the optimization problems which are determined on the basis of social interactions between independent agents. The synthesis problem addressed is to find spatial and feeding configuration of array elements that conform to certain design
constraints enforced on multiple diagrams of differentiated directive gains and values (beam forming). Two different fitness functions were evaluated on this basisC results obtained were correlated to requirements of vertical system integration. The proposed methodology is very flexible allowing the incorporation of additional factors such as coupling characteristics and feeding network constraints.
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