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Circular antenna arrays (CAAs) find extensive utility in a range of cutting-edge communication applications such as 5G networks, the Internet of Things (IoT), and advanced beamforming technologies. In the realm of antenna design, the side lobes levels (SLL) in the radiation pattern hold significant importance within communication systems. This is primarily due to its role in mitigating signal interference across the entire radiation pattern's side lobes. In order to suppress the subsidiary lobe, achieve the required primary lobe orientation, and improve directivity, an optimization problem is used in this work. This paper introduces a method aimed at enhancing the radiation pattern of CAA by minimizing its SLL using a Hybrid Sooty Tern Naked Mole-Rat Algorithm (STNMRA). The simulation results show that the hybrid optimization method significantly reduces side lobes while maintaining reasonable directivity compared to the uniform array and other competitive metaheuristics. [ABSTRACT FROM AUTHOR]

Introduction. Unmanned aerial vehicles (UAVs) are rapidly gaining in popularity. The UVA development requires active antenna systems capable of forming a narrow beam of the main lobe of the radiation pattern. Although numerous studies have considered specialized antenna arrays with a wide range of scanning angles, the location of such systems on UAVs remains under-investigated. The development of such arrays for UAVs will enable the creation of a secure relay broadband channel with a few repeaters.Aim. Development of a broadband antenna array for UAVs with the possibility of setting the main lobe of the radiation pattern in any direction of the azimuthal plane, for use in relay tasks.Materials and methods. An emitter model and a circular antenna array on its basis was developed in the Ansys HFSS electromagnetic modeling package.Results. The dependence of the directional coefficient and the gain for an array consisting of 8 and 16 elements was shown. Voltage standing-wave ratio dependences and directivity patterns that satisfy the conditions of retransmission in a wide-frequency band using UAVs were obtained. Recommendations on the number of active elements in a circular antenna array that ensure the maximum gain (directivity) were formulated.Conclusion. Technical solutions that can be used in the development of UAVs are proposed. The system can be further improved by optimizing the antenna array elements and using a cylindrical or hemispherical array.

Circular antenna arrays (CAAs) find extensive utility in a range of cutting-edge communication applications such as 5G networks, the Internet of Things (IoT), and advanced beamforming technologies. In the realm of antenna design, the side lobes levels (SLL) in the radiation pattern hold significant importance within communication systems. This is primarily due to its role in mitigating signal interference across the entire radiation pattern’s side lobes. In order to suppress the subsidiary lobe, achieve the required primary lobe orientation, and improve directivity, an optimization problem is used in this work. This paper introduces a method aimed at enhancing the radiation pattern of CAA by minimizing its SLL using a Hybrid Sooty Tern Naked Mole-Rat Algorithm (STNMRA). The simulation results show that the hybrid optimization method significantly reduces side lobes while maintaining reasonable directivity compared to the uniform array and other competitive metaheuristics.

A high gain antenna array with reduced side lobe level (SLL) needs to be optimized and designed to meet the requirement of modern wireless communication systems. To achieve this goal, a newly developed natural heuristic algorithm namely sparrow search algorithm (SSA) and its modification are introduced and utilized to the field of electromagnetic optimization for the first time in this paper. Simulation results over several different examples of the linear antenna array (LAA) and circular antenna array (CAA) design problem have been presented to demonstrate the effectiveness and superiority of the modified SSA. The design results obtained by modified SSA showed greater advantages than those certain classical and well-known algorithms like particle swarm optimization (PSO), whale optimization algorithm (WOA) and grasshopper optimization algorithm (GOA), in a statistically meaningful way. [ABSTRACT FROM AUTHOR]

The pattern synthesis of antenna arrays is a substantial factor that can enhance the effectiveness and validity of a wireless communication system. This work proposes an advanced marine predator algorithm (AMPA) to synthesize the beam patterns of a non-uniform circular antenna array (CAA). The AMPA utilizes an adaptive velocity update mechanism with a chaotic sequence parameter to improve the exploration and exploitation capability of the algorithm. The MPA structure is simplified and upgraded to overcome being stuck in the local optimum. The AMPA is employed for the joint optimization of amplitude current and inter-element spacing to suppress the peak sidelobe level (SLL) of 8-element, 10-element, 12-element, and 18-element CAAs, taking into consideration the mutual coupling effects. The results show that it attains better performances in relation to SLL suppression and convergence rate, in comparison with some other algorithms for the optimization case. [ABSTRACT FROM AUTHOR]

Element failure in antenna arrays leads to severe degradation of the radiation pattern. It is significantly more complex in circular antenna arrays (CAA) considering its geometry and elements spatial distribution along the circumference of the circle. Several design parameters like the coefficient of current amplitude excitation, phase, and arc length are determined appropriately to obtain the desired parameters involved in the pattern restoration process. It is possible to rely on alternate desired parameters to restore the patterns without disturbing the actual design parameters involved in the optimization process. In this paper, such an attempt to optimize CAA using non-uniform amplitude distribution is considered. After enforcing multiple-element failure, the resultant defective pattern is restored by determining the non-uniform spatial distribution of four consecutive elements preserving the corresponding non-uniform amplitude distribution. Hence, it is justifying mentioning that the position-only technique is used to restore the pattern in terms of optimized SLL and BW. The spatial distribution of optimized CAA is determined using the latest modified Social Group Optimization Algorithm (MSGOA) and compared the results with the well-known Flower Pollination Algorithm (FPA). The MATLAB ® is used to carry out the simulations, and results are analyzed. [ABSTRACT FROM AUTHOR]

In this paper, equilibrium optimization algorithm (EOA), which is a novel optimization algorithm, is applied to synthesize symmetrical linear antenna array and non-uniform circular antenna array (CAA). The main purpose of antenna array synthesis is to achieve a radiation pattern with low maximum side lobe level (MSL) and narrow half-power beam width (HPBW) in far-field. The low MSL here is an important parameter to reduce interference from other communication systems operating in the same frequency band. A narrow HPBW is needed to achieve high directionality in antenna radiation patterns. Entering the literature as a novel optimization technique, EOA optimally determined the amplitude and position values of the array elements to obtain a radiation pattern with a low MSL and narrow HPBW. The EOA is inspired by models of the control volume mass balance used to predict equilibrium as well as dynamic states. To demonstrate the flexibility and performance of the proposed algorithm, 10-element, 16-element and 24-element linear arrays and eight-element, 10-element and 12-element CAAs are synthesized. The MSL and HPBW values of radiation pattern obtained with the EOA are very successful compared to the results of other optimization methods in the literature. [ABSTRACT FROM AUTHOR]

In this paper, an optimal far-field radiation pattern synthesis by using time modulation technique is carried out for a compact circular antenna array (CAA) design using a stochastic optimization method called krill herd (KH) optimization. A compact antenna array is achieved by reducing the inter-element spacing between the array elements, which leads to the miniaturization of the size of the array. On the other hand, an improved far-field radiation characteristic is achieved with a low side lobe level (SLL) and narrow first null beam width (FNBW). A low SLL is an essential requirement to reduce the interference with the other systems operating in the same frequency band. A narrow FNBW is necessary to obtain a high directivity. In time modulation technique, 'time' has the most significant role. It is considered the fourth-dimensional parameter, which plays the role of an additional degree of freedom to achieve an improved radiation pattern. The time-modulated antenna array (TMAA) radiates at various harmonic frequencies for the periodic switching time sequence. In this paper, the generation of the radiation pattern at the fundamental/central frequency only is considered. The KH algorithm is a flexible and robust search algorithm. It is applied here to find out the optimum sets of switching on-time duration for each array element and to determine the optimum inter-element separation between two array elements of the 20- and 36-element time-modulated circular antenna array (TMCAA). Particle swarm optimization (PSO) and differential evolution (DE) optimization techniques are also individually applied for the same design purpose to prove the superiority of the KH algorithm–based design. Finally, statistical analysis is performed to ensure the significance of the numerical results. [ABSTRACT FROM AUTHOR]

This paper applies time modulation to deal with the design of dual-band antenna arrays in a circular geometry using a micro-strip-fed slot antenna as an element in the frequencies of 2.4 and 5.5 GHz. The motivation for this paper is to exploit the properties and advantages of time-modulated arrays in a dual-band scenario considering a circular geometry. This design considers the optimization of the time switched sequences of the antenna elements in the circular geometry for both operation frequencies. The design process to find the optimal switch- ON intervals of the circular array is carried out by means of the method of differential evolution and particle swarm optimization. The main contribution to the field of this paper is the dual-band performance evaluation of circular antenna arrays considering time modulation and measurements of the antenna element pattern. The performance evaluation and the results and discussion are achieved in terms of the radiation pattern with the measured antenna element, sidelobe level, sideband levels, switching times and efficiency.

The pattern synthesis of antenna arrays is a substantial factor that can enhance the effectiveness and validity of a wireless communication system. This work proposes an advanced marine predator algorithm (AMPA) to synthesize the beam patterns of a non-uniform circular antenna array (CAA). The AMPA utilizes an adaptive velocity update mechanism with a chaotic sequence parameter to improve the exploration and exploitation capability of the algorithm. The MPA structure is simplified and upgraded to overcome being stuck in the local optimum. The AMPA is employed for the joint optimization of amplitude current and inter-element spacing to suppress the peak sidelobe level (SLL) of 8-element, 10-element, 12-element, and 18-element CAAs, taking into consideration the mutual coupling effects. The results show that it attains better performances in relation to SLL suppression and convergence rate, in comparison with some other algorithms for the optimization case.

This paper presents an efficient approach for the design of a non-uniform single ring circular antenna array (CAA) for the synthesis of the optimal far-field radiation pattern. A recently proposed meta-heuristic-based optimization technique known as ant lion optimization (ALO) is applied in this paper to determine the optimum set of current amplitude excitation weights and the inter-element distance among the array elements to reduce the side lobe level (SLL) and 3-dB beam width considering the mutual coupling effect. The results achieved by employing the ALO algorithm are compared with the uniform radiation pattern and with those of the recently reported literature containing equal sets of elements to prove the superiority of ALO algorithm. Three different design examples of 8, 10, and 12 elements CAA are presented, and their performances are compared to illustrate the capability of the ALO algorithm-based approach over those of the recently reported literature. [ABSTRACT FROM AUTHOR]

In this paper, a new metaheuristic, Electric Charged Particles Optimization (ECPO) algorithm, is developed. This algorithm is inspired by the interaction (forces exerted) between electric charged particles. It this algorithm not all the particles interact with each other, only selected ones. Then the way they interact with each other is defined by the selected strategy among the three available strategies. Therefore, there are several combinations possible between the number of interacting particles and strategies to find the most suitable one for the problem in hand which will help the algorithm to solve a wide range of optimization problems. The performance of the developed algorithm is first tested on the set of problems used for single objective real parameter algorithm competition that was held in the congress on evolutionary computation 2014. Then, the ECPO has been applied to optimal design of circular antenna array for sidelobe level reduction. The obtained results are then compared with other well-known metaheuristics using statistical tools. The analysis of the experimental results shows that the ECPO is a very competitive optimization algorithm. [ABSTRACT FROM AUTHOR]

A method of focused delivery of ultrasonic energy to a given point inside a biological object using a circular antenna array is proposed. The functional diagram of a multielement circular array with alternating emitting and receiving elements is presented. The channels of emitting elements contain controlled phase shift modules and all receiving elements are connected to the summator. The possibility of ultrasonic energy focusing is shown by means of modeling of the circular array operation with allowance for the wave propagation in two media. The result of focusing is estimated with allowance for the interface between two media. It is assumed that the two media differ in the propagation speed of the ultrasonic wave. The presence of two media on the propagation path of the ultrasonic wave leads to defocusing and shift of the focus position. [ABSTRACT FROM AUTHOR]

This paper considers circular antenna arrays comprised of symmetrical dipole radiators applied in communication, navigation and monitoring systems. Despite their widespread use, a number of significant issues is underinvestigated. Among them are frequency dependence of the antenna factor (the ratio of the electric field intensity module to the voltage amplitude at the load connected to the output terminals) of the circular antenna array elements in the correct electrodynamic setting. The purpose of this paper is to analyse the antenna factor frequency dependence of a single dipole antenna with different geometry and load both in free space and as circular antenna element. The estimation of phase difference error between the circular antenna array elements caused by their cross coupling is also of interest.Specific expressions are obtained for the antenna factor of the dipole antenna for single-mode and three-mode approximations. The limits of their applicability in frequency band are considered. The solution to the coupled integral equations is obtained using the Galerkin method with piecewise sinusoidal current distribution and with an arbitrary number of basis functions for eight- and four-element circular antenna array. This solution may be generalized to an arbitrary number of circular antenna array elements. It is demonstrated that to improve the antenna factor frequency dependence it is advisable to use dipole antennas with high-resistance load, as well as with large diameter. Phase errors for different circular antenna array element signals are considered with respect to the reference element. The dependence of these phase errors on the circular antenna array geometry is presented. It is concluded that there are significant oscillations of the antenna factor when the dipole is the part of the circular antenna array. They are caused by cross coupling between the circular antenna array elements, which significantly depend on the element spacing. The results presented may be of interest to phase direction finder development engineers.

This paper presents a new approach for circular array of parasitic dipoles composed by one active dipole for reduction of side lobe level with maximum directivity including mutual coupling. The desired goal is obtained by changing the spacing between the parasitic elements and length of the parasitic elements while the position and length of driven element is fixed. In addition to it, reflection coefficient (RC) of the driven element is kept closer to the specified value. Matlab based method of moment code is used to evaluate the performance of circular antenna designs generated by QPSO algorithm. Two examples are presented to show the effectiveness of this proposed approach.

This article shows the design of a non‐uniformly excited single ring circular antenna array (CAA) for the synthesis of optimal far‐field radiation characteristics. A recently proposed meta‐heuristic based optimization algorithm called gray wolf optimization (GWO) and state‐of‐the‐art swarm intelligence based evolutionary optimization technique known as particle swarm optimization with a distribution based update mechanism (PSOd) are individually applied to determine the optimum set of current excitation amplitude weights and the inter‐element spacing among the array elements to reduce the side lobe level and 3‐dB beamwidth considering the mutual coupling. The results obtained by employing PSOd and GWO are compared to those of the uniform radiation pattern and the recently published results of state‐of‐the‐art literature having equal sets of elements to show the superiority of employed approaches. Three different design examples of 8, 10, and 12 elements CAA are reported in this article to study the performances of PSOd and GWO algorithm‐based results over the results of other recently reported literature. [ABSTRACT FROM AUTHOR]

The method for reconstructing object images in cross-sections using a circular antenna array when sounding space by an ultrasonic monochromatic wave is proposed. The image reconstruction is carried out by scanning the internal structure of the object placed inside the circle controlled by the focus of the circular antenna array. An algorithm for controlling the phase shift modules in the elementary radiator channels of the circular antenna array for changing the focus position is presented. Model results of the reconstruction of the image of the simplest point objects are presented. The problems of implementation of a circular array are discussed. [ABSTRACT FROM AUTHOR]

An antenna array is developed to radiate angularly distributed multibeams. The proposed antenna utilizes a 2-D Luneburg lens as a beamforming network (LL-BFN) to produce rotationally symmetric excitations. The concept is to replace an equivalent circular aperture of Luneburg lens by a circular array of excitation output ports. Thus, in addition to the beam selection ports, antenna excitation ports are also established on the LL-BFN to extract the required phases to feed an external circular array of antennas. As a result, more flexible radiation characteristics can be achieved by the circular array. This concept is demonstrated by both simulation and measurement results of an antenna prototype to validate the feasibility. [ABSTRACT FROM AUTHOR]

In this article, a novel electrically controlled optical broadband phase shifter (ECO-BPS) is proposed and experimentally investigated for broadband microwave orbital angular momentum (OAM) mode generation. Based on the proposed ECO-BPS and a 17-element circular antenna array, the effect of the phase error on the OAM mode quality is studied by comparing the OAM modes respectively synthesized by three phase schemes: ideal phase shifts, ECO-BPS phase shifts, and optical true time delay phase shifts. In addition, the crosstalk caused by the phase error in applications of OAM modes multiplexing is investigated in a Dammann vortex grating based OAM modes demultiplexing system. All numerical simulation results demonstrate the feasibility of the ECO-BPS in broadband microwave OAM applications. [ABSTRACT FROM AUTHOR]

Ring antenna arrays find wide application in radio systems of various purpose. However, in many cases it is necessary to use quasi-ring antenna arrays when the emitters are not located in a circle. Such a transition leads to a change in the radiation pattern, i.e. to a shift in its main maximum, an increase in the level of the side lobes, and appearance of two maxima of the radiation pattern. Therefore, to ensure the formation of a directional pattern with specified parameters, it is necessary to correct the amplitude-phase distribution of the quasi-annular antenna array. In this paper, features are considered and an algorithm for the synthesis of the amplitude-phase distribution of a quasi-annular antenna array is developed. The possibilities of preserving the parameters of the directional pattern during the transition from the ring to the quasi-annular antenna array are analyzed.

The characteristics of different architectures antenna arrays with switchable radiation pattern (RP) are investigated. The results of design and development of S-band antenna systems with switchable RP based on planar emitters are presented. The obtained solution minimizes the size and the irregularity of RP in the azimuth plane while providing the required antenna gain. The results of measurements of a prototype are given that demonstrate the possibility of Wi-Fi router input signal increasing up to 10 dB compared to standard antennas.

The resonance type radial slot antenna as a high efficiency Bessel beam launcher was designed and investigated in wide band of operation frequencies. The analytical method to determine resonant frequencies of short-circuit radial line was evaluated and applied to calculation of the resonant frequencies of the radial resonators with different modes number, dielectric permittivity and sizes. The experimental results are in good agreement with calculation once. The expression for E and H are obtained and applied to the calculation of both electric and magnetic fields distributions. The impedance, voltage and current of radial line are investigated and related diagrams of intended modes are plotted. The circular slots are located on the top plate of radial line and are excited by the radialy inward traveling transverse electromagnetic (TEM) mode in the upper part of line. The slots are arrayed on top plate which they can couple with the radial current flowing over the line to produce a radially polarized broadside beam. The position of these radiating slots is estimated from the maximum values of current distribution of line. It was founded that the observe at the distance up to 70λ. [ABSTRACT FROM AUTHOR]

This article presents a versatile pattern synthesis algorithm for controlling the sidelobe level and nulling region for circular antenna arrays. Nonuniform fast Fourier transform using the min-max interpolation method is utilized to overcome the nonlinear feature of circular arrays. The major advantage of the proposed algorithm is low complexity, which is key for hardware implementation. Moreover, the proposed algorithm functions well in amplitude-only pattern synthesis, which may be required for low-cost array systems using attenuators instead of complete amplitude and phase adjustment modules. Additionally, element failure of antenna arrays can be minimized in practical operations by resynthesizing the pattern by using the remaining antennas to achieve satisfactory performance. Simulation results indicate the lower complexity and higher versatility of the proposed algorithm compared with the conventional methods. [ABSTRACT FROM AUTHOR]

Synthesis of non-uniform circular antenna arrays using a hybrid invasive weed optimization is introduced in this paper. The excitation weights and positions of array elements are optimized to reduce the peak side lobe level (PSLL) of the radiation pattern. The method proposed in this paper can effectively constrain the number of the array elements, size of the array, and the angular spacing of the adjacent element simultaneously. The radiation pattern has the constraint of a fixed major lobe beamwidth. Synthesis results of three different circular antenna arrays are given. The results show the effectiveness and feasibility of the proposed synthesis method in non-uniform circular antenna arrays. [ABSTRACT FROM AUTHOR]

In this paper, a uniform circular antenna array (UCAA) combining genetic algorithm (GA) or asynchronous particle swarm (APSO) for finding out global maximum of multi-objective function in indoor ultra-wideband (UWB) communication system is proposed. The algorithm is used to synthesize the radiation pattern of the directional UCAA to reduce the bit error rate (BER), to increase received energy and channel capacity in indoor UWB communication system. Using the impulse response of multipath channel, the BER of the synthesized antenna pattern on binary antipodal-pulse amplitude modulation system can be calculated. Based on topography of the antenna and the shooting and bouncing ray/image techniques, the synthesized problem can be reformulated into a multi-objective optimization problem which would be solved by the GA and APSO. Numerical results show that the fitness value and convergence speed by APSO is better than those by GA. The results also show that for multi-objective problem APSO compared to GA can reduce the BER substantially. Moreover, APSO can get better results for both line-of-sight and non line-of-sight cases. [ABSTRACT FROM AUTHOR]

This paper is aimed at assessing the effectiveness of the phase-only control strategy based on a customized Taguchi method when applied to Uniform Circular Arrays (UCA). The objective of this paper consists to contribute the main lobe optimization of the smart antenna using Taguchi's method. We used the cited method in order to determine phase's weights for each element of the circular antenna array in order to steer the principal lobe from -65° to 65° covering all angular space. After that, we made an electronic platform using the microcontroller STM8S in order to implement an intelligent system. The architecture of this work had used a digital phase shifters, a demodulator AD8347, a modulator AD8349, an array antenna, cards STM8S-Discovery. [ABSTRACT FROM AUTHOR]

The Geostationary Interferometric Microwave Sounder (GIMS) is a new concept of atmospheric microwave sounder for China's future geostationary Earth orbit meteorological satellite (FY-4). It is a microwave interferometric radiometer (MIR) using aperture synthesis and working in rotating time-sharing mode with a circular antenna array. A GIMS proof-of-concept demonstrator operating in the temperature sounding bands of 50-56 GHz has been successfully developed. The instrument uses a circular array with 28 elements (including one in the center of the array). It is capable of imaging a scene with an angular resolution of about 0.08° and a radiometric resolution of less than 1 K with 5-m integration time within a 5° field of view (FOV). Some theoretical aspects of the imaging characteristics of GIMS are discussed, such as the alias-free FOV, angular resolution, radiometric resolution, and imaging algorithm. Some early tests and preliminary imaging experiments of the GIMS demonstrator are also presented. [ABSTRACT FROM PUBLISHER]

The vortex electromagnetic (EM) wave, which carries orbital angular momentum (OAM), is exploited to multitarget detection applications. The detection model in the squint mode is derived first. The elevation and azimuth angles of the targets are estimated by the fast Fourier transform method and validated by the simulation. Subsequently, proof-of-concept experiments are performed to validate the principle of the proposed OAM-based target detection technique. The signal processing method for the real-world data obtained from the experiments is proposed to identify the positions of the targets. Experimental results demonstrate the effectiveness of the proposed detection method and indicate that the vortex EM wave can readily be applied to detect multiple targets simultaneously. The work and results show the new applications of the vortex EM wave as well as the development of the novel radar detection technology. [ABSTRACT FROM PUBLISHER]

In this paper, a new model for suppressing jammers to GPS receivers is proposed. In the model, circular antenna arrays combining minimum norm (min-norm) and linearly constrained minimum variance (LCMV) algorithms have been used for signal anti-jamming. Six GPS signals' and two jammers' original incident direction were assumed respectively. The simulation was performed with a variation of the power of the two jammers and the element number of the circular antenna array. The simulation result indicates that by utilizing this new signal suppression model, nulls depths assigned to the jammer reach -238dBW when the number of element of circular antenna array is assumed to be 30. It also indicates that the stronger power of the jammer, the deeper nulls depths can be assigned with this new signal processing structure.

The design of a radio communication system employing orbital angular momentum (OAM) mode multiplexing is described. Rotman lenses followed by circular antenna arrays are used to transmit and receive radio frequency beams carrying OAM. In our experiment, two 3 \times 3 Rotman lenses are fabricated to feed the three-element circular arrays with certain phase gradients for OAM modes multiplexing and demultiplexing. The OAM-carrying beams of mode number l = +1, 0,\, \text{and} -\!\!1 are generated at 9.7 GHz, with each channel carrying an independent data stream of 40 Mbit s \mathbf{^{-1}}$ quadrature phase shift keying signal in a bandwidth of 20 MHz. And all three channels are recovered with bit error rates below the forward error correction limit of 3.8\times 10\ \mathbf{^{-3}}. [ABSTRACT FROM PUBLISHER]

• The optimization problem is formulated for CAA to achieve the desired FOM. • Meta-heuristic algorithm is proposed to generate quick, low cost and robust solutions. • Performance of the algorithm is verified for the different hard controlled variables. • The 3Dradiation pattern results are also tested to validate the desired FOM. In many wireless applications, circular antenna arrays are commonly used but managing the lower side lobe with high directivity is still challenging. Many typical methods could be used to synthesize the array in real time but lag behind to retain high directivity and the low sidelobe level. This study formulates an optimization problem to obtain the desired main lobe direction, suppress the subsidiary lobe, and maximizes the directivity. A modified optimization algorithm is proposed called Integrated Harmony Search with Differential Evolution based Naked Mole Rat Algorithm (IHDN) to rapidly and reliably refine control parameters. Simulations are performed, and results are compared to other traditional algorithms. The findings show that the proposed algorithm results in excellent side lobe minimization with good directivity. The size analysis indicates that good directivity values with low sidelobe levels can be obtained for a smaller number of antenna elements. [ABSTRACT FROM AUTHOR]