Efficient and Accurate Synthesis for Array Pattern Shaping

It is shown that the radiation pattern of a hexagonal planar array with triangular arrangement of elements can be synthesized by using a pattern of a linear array. The resulting pattern has the same sidelobe level as the corresponding linear array pattern. The current amplitude of the array element is represented by a linear combination of the current amplitudes of linear array elements with constant coefficients.

A flexible search technique based on a tabu search algorithm is presented for the shaped‐beam pattern synthesis of linear antenna arrays. To synthesize a desired pattern, element excitations and/or positions are optimally determined. Examples of cosecant, flat‐topped, and pencil beam patterns are given to illustrate the achievable performance. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 16–20, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10657

The pattern synthesis technique of antenna arrays has a wide range of applications in radar and communication systems, which is an important research direction in the field of smart antennas. In order to improve the optimization performance of pattern synthesis of linear antenna arrays, an optimization method based on the Modified RIME Optimization Algorithm (MRIME) is proposed. RIME is a new heuristic algorithm inspired by the condensation process of frost ice in nature, which has a unique update mechanism with strong convergence as well as randomization. In the present work, MRIME is used for optimal pattern synthesis of a linear antenna array (LAA). One part of the present study is to optimize the side lobe level by optimizing the antenna current amplitude while maintaining a uniform spacing; the other part is to optimize the antenna position while assuming a uniform excitation in the synthesis of a sparse LAA, where constraints are imposed on the spacing of the array elements and aperture length, and suppression of the side lobe level with the position of the zeros in the specified direction is also achieved. In this article, simulation experiments for uniform linear arrays as well as sparse linear arrays are presented in detail, and the results show that the MRIME optimization algorithm outperforms most of the existing evolutionary classes of optimization algorithms in optimizing the side lobe level. This illustrates the potential of utilizing the MRIME optimization algorithm for antenna arrays and various other electromagnetism-related challenges.

Radiation pattern of linear arrays of microstrip rectangular antennas, on uniaxial anisotropic substrate is presented with Galerkin method. An optimization procedure based on the genetic algorithm (GA) method is introduced to reduce the side lobe level (SLL), by acting on the law of current amplitude of feed, spacing and phase of a linear array antennas. The results of optimisation are verified shows of narrow beamwidth are achieved.

An improved technique is presented for synthesizing a linear antenna array pattern with multiple prescribed broad nulls. The array pattern synthesis problem is formulated as a least-squares optimization problem. A computation method based on matrix factorization is developed for reducing the computational complexity of determining the optimal weight vector. In order to use this technique in HF radar systems in real time mode, a formula is derived to reduce the storage and computational complexity of the algorithm. Finally, simulation results demonstrate the capability of this technique in forming nulls in the prescribed directions.

The paper presents design and development of a linear microstrip patch antenna array and also, a method to change the radiation pattern of the array by steering null in the desired direction. This is achieved by changing the phase of each of the array element which produces a null in the radiation pattern without significantly affecting the main beam lobe. Different methods can be used for array synthesis. In this paper the Schelkunoff polynomial method is used for the synthesis of array. For an N element array, (N-I) nulls can be formed. The array is designed around a frequency of 930 MHz using four microstrip patch antenna elements of rectangular shape arranged in linear configuration. The theoretical design of the antenna array is presented initially and then the results of the array simulation and the hardware implementation are presented.

In time-modulated antenna arrays (TMAAs), as a result of periodical switch-on and switch- ofi of the antenna elements, including operating frequency (termed as center frequency) signal, sideband signals are appeared at either sides of the center frequency in integer multiples of the modulation frequency. In this paper, it is shown that without using phase shifters, just by suitably controlling the on-time instants (OTIs) and on-time durations (OTDs) of a time-modulated linear antenna array (TMLAA) elements, simultaneously, along with a pencil beam pattern at the operating frequency, a shaped beam pattern can be obtained at both the flrst positive and negative harmonics of the time- modulation frequency. The important advantage of such a technique is that realization of multi-beam pattern in conventional antenna array (CAA) system generally requires complex feed network, whereas by using simple radio frequency (RF) switching circuit in the feed network of TMLAA, by virtue of the properties of harmonic radiations, synthesis of a shaped pattern at either (positive or negative) harmonic results in generating the same pattern in its opposite harmonic, and the synthesized patterns at difierent harmonics can be simultaneously used as independent communication channels. By employing a difierential evolution (DE) based optimization method, numerical results for a 16-element TMLAA with uniform excitation show that in conjunction with a pencil beam pattern at the center frequency, a ∞at-top or a cosec square pattern at flrst positive and negative sidebands of side-lobe levels (SLL) i20dB can be synthesized by suppressing the higher sideband level (SBL) to below i10dB.

This paper introduces an application of the dandelion optimization (DO) algorithm in antenna arrays. This is the first time that the DO algorithm has been used for optimizing antenna arrays. For antenna array optimization, sidelobe level (SLL) and deep nulls are key technical indicators. A lower SLL can improve the signal-to-noise ratio and reduce the impact of clutter signals outside the main beam. Deep nulls need to be aligned with the direction of interference to eliminate the influence of interference sources. The combination of the two can effectively improve the anti-interference ability of the entire system. Therefore, antenna arrays with ultra-low sidelobes and ultra-deep nulls are currently hot in the field of antenna array design and are also some of the key technologies needed to achieve modern high-performance radar systems. As a new type of evolutionary algorithm inspired by nature, the DO algorithm is inspired by the wind propagation behavior of dandelions in nature. This algorithm iteratively updates the population from three stages of ascent, descent, and landing, ultimately finding the optimal position. It has good optimization ability in solving complex problems such as those involving nonlinearity, discreteness, and non-convexity, and the antenna array pattern synthesis optimization problem belongs to multivariate nonlinear problems. Therefore, the DO algorithm can be effectively applied in the field of antenna array optimization. In this work, we use the following method to obtain an optimized pattern of a linear array with the lowest sidelobe level (SLL), null placement in particular directions, and a lower notch in particular directions: by controlling the antenna array’s element spacing and leaving the phase unchanged to optimize the current amplitudes and by controlling the excitation current and phase fixation of the antenna array and changing the element spacing. In the first and second examples, different algorithms are used to reduce the SLL of the antenna. In the first example, the DO algorithm reduces the SLL to −33.37 dB, which is 2.67 dB, 2.67 dB, 3.77 dB, 2.74 dB, and 2.52 dB lower than five other algorithms. In the second example, the SLL optimized by the DO algorithm is −42.56 dB, which is 5.04 dB and 1.48 dB lower than two other algorithms. In both examples, the DO algorithm reduces the SLL lower than other algorithms when the main lobe of the antenna is not significantly widened. Examples 3, 4, and 5 use the DO algorithm to optimize the amplitude of the current, generating deep nulls and deep notches in specific directions. In Example 3, the DO algorithm obtains a depth of nulls equal to −187.6 dB, which is 66.7 dB and 44.3 dB lower than that of the flower pollination algorithm (FPA) and the chaotic colony predation algorithm (CCPA), respectively. In Example 4, the deep null obtained by the DO algorithm is as low as −98.69 dB, which is 6.67 dB lower than the deep null obtained by the grey wolf optimization (GWO) algorithm. In Example 5, the deep notch obtained by the DO algorithm is as low as −63.1 dB, which is 6.4 dB and 1.9 dB lower than the spider monkey optimization (SMO) algorithm and the grasshopper optimization algorithm (GOA), respectively. The data prove that the DO algorithm produces deeper nulls and notches than other algorithms. The last two examples involve reducing sidelobe levels and generating deep nulls by optimizing the spacing between elements. In Example 5, the SLL obtained using the DO algorithm is −22.8766 dB, which is 0.1998 dB lower than the lowest SLL of −22.6768 dB among other algorithms. In Example 6, the SLL obtained using the DO algorithm is −20.1012 dB, and the null depth is −125.1 dB, which is 1.592 dB lower than the SLL obtained by the cat swarm optimization (CSO) algorithm and 19.1 dB lower than the deep null obtained by the GWO algorithm, respectively. In summary, the results of six simulation experiments indicate that the DO algorithm has better optimization ability in linear array optimization than other evolutionary algorithms.

This paper presents a new scheme based on Weight vector ORthogonal Decomposition (WORD) to control the array response at a given direction and a novel WORD-based approach to pattern synthesis for arbitrary arrays. The central concept of the proposed methods stems from the adaptive array theory. More precisely, it is found that the inverse of the noise-plus-interference covariance matrix in adaptive beamforming can be regarded as a linear combination of two orthogonal projection matrices, and, accordingly, the optimal weight vector is a linear combination of two orthogonal vectors. With such an observation, the WORD scheme is developed to design the desired weight vector. It is shown that the array response at a given direction can be precisely adjusted to an arbitrary level, by simply determining appropriate combination coefficients for those two orthogonal vectors. Furthermore, a closed-form expression of the weight vector can be achieved by introducing a new cost function that measures pattern variation. By employing the WORD scheme successively, a novel approach to pattern synthesis for arbitrary arrays is devised. At each implementation step of this approach, the array pattern is adjusted in a point-by-point manner by successively modifying the weight vector. As such, both the sidelobe and mainlobe regions can be flexibly synthesized. Numerical examples are provided to demonstrate the effectiveness and flexibility of the WORD scheme in array response control at a single direction as well as pattern synthesis.

In this paper a method using artificial neural networks (ANN) has been developed to identify the fault elements in linear array antennas. The ANN forms a mapping between the radiation pattern of the faulty array with the faulty element position. After proper training, the response time of the ANNs is very fast in identifying even the partially fault elements. The present work can also be extended for planar arrays of different kinds

Most of the recent state of the art circular antenna arrays (CAA) synthesis techniques attempted to synthesize the Chebyshev linear array patterns in the azimuth plane. In this paper, a new Genetic algorithm optimization-based technique for Uniform CAAs synthesis to realize a desired Chebyshev pattern in the elevation plane is introduced. The proposed technique maintains the same number of antenna elements as the linear antenna array. While the CAA diameter, elements angular distribution, and elements excitations are optimized to synthesize the desired pattern. The CAA diameter is optimized around the array size of the linear antenna array. And the angular positions of the antenna elements are non-uniformly distributed on the circle circumference using the GA optimization. While a closed-form expression for the corresponding elements excitations is derived to determine these excitations using a deterministic equation solving technique. Several simulations are performed to verify the effectiveness of the proposed technique.

A problem of sidelobe suppression of a uniformly excited circular array of monopoles through the adjustment of the excitation phases is dealt with. For this purpose, the method of approximation programming (MAP) is used to determine the optimum excitation phases which minimize the sidelobe level. Galerkin's method is used to analyze the mutual coupling between array elements. The resulting radiation pattern has equal amplitude sidelobes that are lower than those obtained with a cophasal array. The resulting radiation pattern of a 32-element double-ring array, operating at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</tex> -band, was measured and reasonable agreement with theory was obtained.

The synthesis of a nonuniform antenna array with as few elements as possible has considerable practical applications. This paper introduces a new non-iterative method for linear array synthesis based on the matrix pencil method (MPM). The method can synthesize a nonuniform linear array with a reduced number of elements, and can be also used to reduce the number of elements for linear arrays designed by other synthesis techniques. In the proposed method, the desired radiation pattern is first sampled to form a discrete pattern data set. Then we organize the discrete data set in a form of Hankel matrix and perform the singular value decomposition (SVD) of the matrix. By discarding the non-principal singular values, we obtain an optimal lower-rank approximation of the Hankel matrix. The lower-rank matrix actually corresponds to fewer antenna elements. The matrix pencil method is then utilized to reconstruct the excitation and location distributions from the approximated matrix. Numerical examples show the effectiveness and advantages of the proposed synthesis method.

In this paper two broadside Omni antennas are proposed. The proposed antennas are a novel design with broadside omni directional patterns of medium and high gains having 360° coverage across the azimuth or Yaw plane and su cient coverage in elevation or roll plane. These antennas are the best candidate for UAVs RF link having smartest hardware with ease of installation and negligible structural drag. The proposed medium gain antenna is a special type of dipole antenna having omni directional radiation characteristics. The dipole is excited through coaxial feeding. Similarly proposed high gain antenna is a special type linear dipole antenna array (2×1) having omni directional radiation characteristics with increased gain in horizon plane. The array elements are also excited through cascaded coaxial feeding. These antennas are designed in S-Band with 25% impedance bandwidth at f o . The main lobe of single element antenna is exactly at horizon which is usually not the case in many designs. The gain of the two element array antenna is 5dBi which is very useful in increasing the line of sight range of UAVs.

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.