Pattern Synthesis Method Research Articles

AN ALTERNATIVE METHOD FOR DIFFERENCE PATTERN FORMATION IN MONOPULSE ANTENNA

Difierence patterns are vital for the successful function of tracking radar employing monopulse techniques to estimate target direction. Traditional monopulse antenna pattern synthesis methods require the use of two independent distributions, e.g., Taylor and Bayliss distributions, for formation of sum and difierence patterns for one antenna. Hence, these approaches require a feed network of considerable complexity. In this letter, a method for forming difierence pattern in linear arrays using a very simple beamforming network and two additional elements is described. The sum pattern is determined by adding signals received by original radiating elements of the array whereas the difierence pattern is determined by subtracting the output of the sum pattern from signals received from two external edge elements. The proposed method used to generate these two patterns ofiers signiflcant hardware and software savings over current methods.

Pattern synthesis method applied in designing HF superdirective receive arrays

Pattern synthesis method applied in designing HF superdirective receive arrays

Pattern synthesis for multi-feed reflector antennas using invasive weed optimisation

The authors present a new optimisation method for pattern synthesis of multi-feed reflector antennas in this study. By using an invasive weed optimisation (IWO) algorithm, shaped beam antennas are designed. The results of the IWO algorithm for the synthesis of cosecant squared and contoured beam patterns are presented and compared with particle swarm optimisation algorithm results. The far-field radiation patterns of reflector antennas, fed by linear and planar array of conical horn antennas, are provided by a physical optics and the error between desired and provided radiation patterns is calculated by a root mean square method. The results show that the IWO algorithm, which provides good convergence, is stable and adaptive-to-change for different boundary conditions in pattern synthesis applications.

An iterative FFT based flat-top footprint pattern synthesis method with planar array

A pattern synthesis technique for the flat-top pattern with an arbitrary footprint is proposed in this paper. This technique is based on an iterative fast Fourier transform (FFT) method and the Elliott–Stern method. Due to the Fourier transformation-pair relationship between the array excitations and the array factor, the iterative FFT method is used to adjust the array factor iteratively to obtain the desired pattern. To accelerate this method and to make this method more robust, the initial element excitations are obtained by applying Fourier transform to a pattern designed by the Elliott–Stern method. Several numerical simulations are applied to validate the effectiveness of this technique.

Minimization in variations of different parameters in different φ planes of a small-size concentric ring array antenna using firefly algorithm

The radiation pattern of a small-size concentric ring array antenna does not remain φ-symmetric, if the array is made with an appreciably lesser number of antenna elements. The sidelobe level, first null beamwidth (FNBW), half-power beamwidth (HPBW), and the null depths of the radiation pattern change significantly in different φ planes. An efficient pattern synthesis method has been developed in this work to reduce the variation of sidelobe level, FNBW, and HPBW of a small-size concentric ring array of isotropic antennas, for different φ cuts. It is done by finding out an optimum set of amplitude distribution of the array elements using firefly algorithm. The sidelobe level and the first null depth of the array are kept below a desired value for all the defined φ cuts. The directivity of the optimized array and the uniform array has been computed. The variation of all these parameters for different φ cuts has been compared to the same array with uniform excitation among the elements.

Differential Evolution and Genetic Algorithm for Sidelobe Reduction of A Concentric Ring Array Antenna by Radial Variation of Amplitudes With Fixed and Variable First Null Beamwidth

Reduction of side lobe levels in a concentric ring arrays results in wide first null beamwidth. The authors propose a pattern synthesis method based on the Differential Evolution (DE) algorithm to reduce the side lobe levels of a concentric ring array of isotropic antennas while keeping the first null beamwidth (FNBW) fixed and variable by radial variation of amplitudes of the array elements. Two different cases have been studied, one with fixed initial interelement distance and another with optimum interelement distance for the entire array. The FNBW of the optimized array is kept equal to or less than that of a uniformly excited and 0.5 λ spaced concentric ring array of the same number of elements and rings. Results are also compared with Genetic Algorithm to establish its superiority.

Synthesis of thinned planar concentric circular antenna arrays using biogeography-based optimisation

This study presents a novel optimisation algorithm biogeography-based optimisation (BBO) for thinning large multiple concentric circular ring arrays. The objective is to achieve an array of uniformly excited isotropic antennas that will generate a narrow beam with minimum relative sidelobe level (SLL). BBO is a new comprehensive force based on the science of biogeography. Biogeography is the schoolwork of geographical allotment of biological organisms. BBO utilises migration operator to share information between the problem solutions. The problem solutions are known as habitats and sharing of features is called migration. In this study, the authors propose pattern synthesis method to reduce the SLLs with narrow beamwidth (BW) by making the ring array thinned using the BBO algorithm. The thinning percentage of the array is kept equal to or more than 50% and the BW is kept equal to or less than that of a fully populated, uniformly excited and 0.5λw, spaced concentric circular ring array of same number of elements and rings. The results obtained are compared with previous published results of modified particle swarm optimisation and differential evolution with global and local neighbourhoods.

Time Reversal Based Broadband Synthesis Method for Arbitrarily Structured Beam-Steering Arrays

We propose a novel broadband beam pattern synthesis method to synthesize arbitrarily structured beam-steering arrays by utilizing time reversal technique. Unlike conventional frequency-domain array synthesis methods, this method achieves array excitation by taking the Fourier Transform of the time reversed version of the transient signals received by antenna elements. Using this method, designers can determine the array excitation over a wide frequency range at once by a single run of time reversal experiment, instead of performing time-consuming multi-objective optimizations of beam pattern cost-functions at each frequency. Furthermore, it does not require explicit measurements of element mutual coupling and platform scattering effects since the time reversal signals have implicitly taken into account those effects. The proposed method is theoretically analyzed with the antenna reciprocity and numerically validated with three dipole arrays of different configurations. The results show that this new method is capable of realizing accurate beam steering over a wide frequency band if the desired steering angle is located in the feasible angular scope of beam scan. The beam patterns with accurate beam steering are successfully achieved over a bandwidth of more than 1.5 GHz for three different dipole arrays, i.e., a typical linear dipole array, a grounded circular dipole array, and a dome-shaped dipole array.

Array pattern synthesis using sparse representation of beampattern

A new array pattern synthesis method is proposed by using the concept of a sparse representation of beampattern, in which array pattern synthesis is achieved by evaluating the sparsity of beampattern and combining with a set of constraints on magnitude response. The proposed method can not only achieve a low sidelobe level, but also flexibly control the robust response region with specified beamwidth and response ripple.

Sum, Difference and Shaped Beam Pattern Synthesis by Non-Uniform Spacing and Phase Control

A design procedure for the synthesis of non-uniformly spaced linear arrays is presented, which uses the Poisson sum expansion of the array factor introduced in the literature. By considering the nonzero phase term in the existent formula and using the appropriate line source pattern synthesis methods, a general design procedure is obtained to synthesize any type of pattern, such as sum, difference and shaped beams. This approach converts the nonlinear complex problem of pattern synthesis for non-uniformly spaced linear arrays to a simple problem, which makes it fast and easy to implement. Moreover, an extra optimization process is added to the synthesis procedure to improve final pattern and provide control on computed parameters.

Pattern Synthesis Method for Arbitrary Arrays

该文提出一种新的基于优化理论的方向图综合算法。该方法先利用与相位无关的约束得到期望主瓣，再利用优化方法求解残余权矢量获得期望旁瓣，使残余权矢量对主瓣的影响控制在一定范围内，优化问题可看作是二次锥规划(SOCP)。与传统的对模值和相位均进行约束的综合方法相比，该方法要求综合期望方向图的模值，不仅能够有效地获取期望方向图，而且主瓣控制机制与参考点的选取无关。对多种任意阵的仿真结果证明该方法的有效性和正确性。

Adaptation of Schelkunoff's Superdirective Antenna Theory for the Realization of Superoscillatory Antenna Arrays

We have adapted Schelkunoff's method of antenna pattern synthesis to the design of superoscillatory waveforms. Our method stems from the observation that superdirectivity and superoscillation are dual phenomena in the space and spectral domains; it can be applied to construct any periodic superoscillatory wave functions. Using this method, we designed two subwavelength focusing schemesin free space and within a waveguideat an image distance of five wavelengths. We first describe how we extend the concept of superdirectivity toward constructing superoscillatory waveforms, then provide in-depth formulations as they apply to each design example. We also report full-wave simulation results verifying subwavelength focusing to 0.6 times that of the diffraction limit at a distance five wavelengths away from the source.

COMPARATIVE PERFORMANCE OF GRAVITATIONAL SEARCH ALGORITHM AND MODIFIED PARTICLE SWARM OPTIMIZATION ALGORITHM FOR SYNTHESIS OF THINNED SCANNED CONCENTRIC RING ARRAY ANTENNA

Scanning a planar array in the x-z plane directs the beam peak to any direction ofi the broadside along the same plane. Reduction of sidelobe level in concentric ring array of isotropic antennas scanned in the x-z plane result in a wide flrst null beamwidth (FNBW). In this paper, the authors propose pattern synthesis methods to reduce the sidelobe levels with flxed FNBW by making the scanned array thinned based on two difierent global optimization algorithms, namely Gravitational Search Algorithm (GSA) and modifled Particle Swarm Optimization (PSO) algorithm. The thinning percentage of the array is kept more than 45 percent and the flrst null beamwidth (FNBW) is kept equal to or less than that of a fully populated, uniformly excited and 0:5‚ spaced concentric circular ring array of same scanning angle and same number of elements and rings.

Pattern Synthesis of Sparse Phased Array Antenna Using Genetic Algorithms

Sparsely sampled irregular arrays and random arrays have been used or proposed in several fields such as radar, sonar, and ultrasound imaging. One method of pattern synthesis for sparse phased array antenna using genetic algorithms is introduced. We start with an introduction to genetic algorithms and then consider the problem of finding the best amplitude layout of elements in sparse arrays. The optimization criteria are then reviewed: creation of beam patterns with low main lobe width and low side lobes.

Mutual Coupling Compensation in Arrays Using a Spherical Wave Expansion of the Radiated Field

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This letter presents a flexible method to compensate the interelement mutual coupling (MC) effects that may degrade the field pattern of an array of real and coupled antennas. A closed-expression for a mutual coupling compensation matrix (MCCM) is derived. The MCCM is used to compensate the presence of the real individual elements' patterns and the interelement MC effects for any excitations obtained with an isotropic-based pattern synthesis method. The MCCM is calculated from the generalized scattering matrix (GSM) of an antenna array and the spherical mode expansion (SME) of its radiated field. For a given array, this MCCM has to be calculated only once since it only depends on the radiating and scattering characteristics of the antenna elements as well as on their location in the array. Conditions regarding null field pattern directions can also be reinforced in the MCCM. To compute the GSM of the array and the SME of the radiated field, a validated full-wave hybrid and modular methodology is used. Numerical results of synthesized patterns where the MC effects have been compensated are presented for arrays made up of dielectric resonator antennas. </para>

Frequency-invariant pattern synthesis of conformal array antenna with low cross-polarisation

Despite their potential and promising advantages over classical planar arrays, conformal arrays also present many challenges to the antenna designer, including varying element normal due to curvature, serious cross-polarisation effect, limited operational bandwidth and so on. A uniform method for the element polarised pattern transformation of arbitrary 3D conformal arrays is presented based on Euler rotation. A space–time-polarisation filter structure is proposed for the pattern synthesis of conformal array, in which the finite impulse response (FIR) filters assigned to every element are used to acquire the frequency-invariant array pattern and the element polarisation diversity in array global coordinates is used to depress the cross-polarisation level. The optimal weight vector is obtained by alternating projection method. The alternating projection method is a powerful and attractive method for the pattern synthesis in that it requires relatively smaller amount of computation burden and a wide variety of desirable constraints can be freely implemented in a ‘visible’ way, which is usually impossible for other optimisation method. The pattern synthesis method proposed has established a unified frame for the frequency-invariant and low cross-polarisation pattern synthesis of conformal array. Simulation results are provided to demonstrate the effectiveness and behaviour of the proposed method.

Improvement of Beam Scanning Characteristics of a Dielectric Lens Antenna by Array Feeds

In the Intelligent Transportation System, millimeter waves are used and antennas are required beam scanning ability. In the millimeter wave operation, a lens antenna is one of the prominent candidates which achieves wide angle beam scanning. Wide angle scanning can be achieved by introducing Abbe sine condition to lens surface shaping. Authors designed the shaped lens antenna that could achieve beam scanning ±30°. The narrow beam widths were maintained on the scanning plane. However, the beam widths were broadened on the transverse plane and large gain reduction was appeared. It was clarified that the reason of this beam deterioration was due to the phase delay on the antenna aperture. In this paper, an array feed composed of a group of rectangular horns is employed to compensate the phase delay on the antenna aperture. In designing the array feed, because there were no examples of phase radiation pattern synthesis, a new radiation pattern synthesis method is studied. Ability of the weighting matrix contained in the Least Mean Square synthesis method is paid attention. Adequate weighting matrix is found out. Satisfactory phase radiation pattern that can compensate the phase delay and an adequate amplitude radiation pattern are achieved. As a result, the improvement of scanned beam widths and antenna gains through the array feed are ensured. And adequate horn arrangements of the array feed for improving scanned beam are clarified. Moreover, in order to examine the realization of an actual array feed, the exact electromagnetic simulation is conducted. The validity of the radiation pattern synthesis is clarified.

Fast Low-Sidelobe Synthesis for Large Planar Array Antennas Utilizing Successive Fast Fourier Transforms of the Array Factor

A new and very fast low-sidelobe pattern synthesis method for planar array antennas with periodic element spacing is described. The basic idea of the method is that since the array factor is related to the element excitations through an inverse Fourier transform, the element excitations can be derived from the array factor through a direct Fourier transform. Starting with an initial set of suitable element excitations the array factor is calculated. After matching the array factor to the prescribed pattern, an updated set of excitations is obtained through a direct Fourier transform performed on the matched array factor. From this updated set, only the samples associated with the aperture are retained, where after a new array factor is calculated. The whole process is repeated until the updated array factor does not violate any longer the pattern requirements. The proposed synthesis method provides significant improvements in terms of performance, computational speed, flexibility, and ease of implementation in software to the methods described in reviewed literature. A number of representative examples are presented to demonstrate the various unique capabilities of the method. The results include sum and difference patterns for circular and elliptical aperture shapes featuring uniform ultra low sidelobes

Partition based pattern synthesis technique with efficient algorithms for nearest neighbor classification

Nearest neighbor (NN) classifier is a popular non-parametric classifier. It is conceptually a simple classifier and shows good performance. Due to the curse of dimensionality effect, the size of training set needed by it to achieve a given classification accuracy becomes prohibitively large when the dimensionality of the data is high. Generating artificial patterns can reduce this effect. In this paper, we propose a novel pattern synthesis method called partition based pattern synthesis which can generate an artificial training set of exponential order when compared with that of the given original training set. We also propose suitable faster NN based methods to work with the synthetic training patterns. Theoretically, the relationship between our methods and conventional NN methods is established. The computational requirements of our methods are also theoretically established. Experimental results show that NN based classifiers with synthetic training set can outperform conventional NN classifiers and some other related classifiers.

3-D array pattern synthesis with frequency Invariant property for concentric ring array

This correspondence proposes a method for array pattern synthesis of a concentric ring array that yields invariant array pattern over a certain frequency band for beamforming in three dimensions. The proposed method uses the Fourier-Bessel series to determine the weights from different rings to form the overall array pattern. Simulation examples are given to illustrate the proposed method.