Analytical array polynomial method for linear antenna arrays with phase-only control

A simple yet reliable approach to a rapid design closure of linear antenna array apertures at the electromagnetic (EM)-simulation level is proposed. Our methodology exploits an underlying array factor (AF) model suitably corrected by means of characteristic points (angles and levels) of the radiation pattern of the EM model of the antenna array aperture. This conveniently allows for controlling both the sidelobe levels and the main beamwidth of the radiation pattern. The surrogate model constructed using the characteristic points is iteratively updated and reoptimized within the trust-region-embedded gradient-search framework. Considerable design speedup is achieved by exploiting correlations between the AF and EM models. The proposed algorithm is demonstrated using 12-, 24-, and 36-element linear microstrip antenna array apertures with the optimum designs obtained at the cost of a few EM simulations of the respective structures.

A systematic approach to sidelobe reduction of broadside linear antenna arrays using corporate feeds implementing non-uniform excitation is proposed. Only the corporate feeds that consist of equal-power split T-junctions, i.e., the simplest power dividers, are considered. First, for a given particular array aperture, candidate feeds (excitation sets) are searched among excitation sets which might energize the aperture. The search is performed over all realizable excitations using the array factor and the model of excitation amplitudes due to power distribution within the feed. At the second stage, an excitation that provides reduced sidelobes and simple routing is implemented as a microstrip corporate feed. Finally, the entire antenna-feed circuit is tuned and validated using numerical optimization and discrete electromagnetic simulations at the high-fidelity level of description. Our approach offers flexibility in design of linear antenna arrays without introducing extra hardware complications. A case study of a twelve-element microstrip array-feed circuit explains and demonstrates our approach.

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.

본 논문에서는 선형 위상 배열 안테나 패턴 합성 문제에서, 주 빔 패턴 양쪽에 임의로 설정한 비대칭 sidelobe 레벨(SLL)들을 만족시키는 안테나 소자 가중치들을 계산하는 방법을 새로이 제안한다. 소자 가중치들을 배열인자로부터 직접 최적화하는 기존의 방법들과는 달리, 이 방법은 배열 인자를 표현하는 Schelkunoff 다항식에 내재된 복소근의 최적 섭동에 기본을 둔다. 제안한 방법으로부터 여러 개의 jammer들의 방향으로 다중 nulling도 가능하며, 이는 각 jamming 방향에 대응하는 복소근들만의 독립적인 섭동에 의해 이루어진다. 따라서 해 공간차원의 적절한 감소에 의해 수치적 절차가 간소화될 수 있다. 또한 배열 소자들의 복소 가중치들은 최적 섭동된 복소근들을 Schelkunoff 다항식에 대입함으로써 쉽게 계산된다. 몇 가지 예를 들어 검토하고, 도출된 가중치들을 배열 인자 방정식에 대입함으로써 타당성을 수치적으로 검증한다. This paper newly proposes a methodology towards computing antenna element weights which are satisfying asymmetric sidelobe levels(SLLs) specified arbitrarily on both sides of the main beam pattern, in the linear phased array antenna pattern synthesis problem. Opposite to the conventional methods in which the element weights are directly optimized from the array factor, this method is based on the optimum perturbations of complex roots inherent to the Schelkunoff's polynomial form which is described for the array factor. From the proposed methodology, the capability of nulling the directions of multiple jammers is also possible by independently perturbing only the complex roots corresponding to each jamming direction, hence allowing an enhancement of the simplicity of the numerical procedure by means of a proper reduction of the dimension of the solution space. The complex weights over the array are then easily computed by substituting the optimally perturbed complex roots to the Schelkunoff's polynomial. Some examples are examined and numerically verified by substituting the extracted weights into the array factor equation.

In this article, a metasurface (MS) is placed as superstrate to counteract the effect of mutual coupling in linear antenna array in X-band. The metasurface is single layered and consist of single split ring resonator (SRR) and two I-shaped structures. The proposed metasurface can curb the interactions between adjacent antenna elements by collimating the electric field and reduce horizontal magnetic field interactions due to its negative refractive index and mu-near-zero property. The functioning of metasurface is tested by placing it above a 1×3 patch antenna. The experimental measurement shows an isolation below -25 dB in the 5.12% operational bandwidth with maximum isolation of -38.2 dB for an edge-to-edge distance of only 0.16λo. The active radiation pattern indicates an improved cross-polarization levels to below -30 dB, in both the orthogonal planes. The performance of MS is further tested for a 1×7 linear array where a 9.2 dB reduction in coupling value is observed. On placing the MS on the array there is no change in the operational bandwidth indicating that no modifications is needed in the antenna array geometry making it a preferable and easily transferrable solution to already existing antenna array.

This book presents a new global optimization technique using Taguchi’s method and its applications in electromagnetics and antenna engineering. Compared with traditional optimization techniques, Taguchi’s optimization method is easy to implement and very efficient in reaching optimum solutions. Taguchi’s optimization method is developed based on the orthogonal array (OA) concept, which offers a systematic and efficient way to select design parameters. The book illustrates the basic implementation procedure of Taguchi’s optimization method and discusses various advanced techniques for performance improvement. In addition, the integration of Taguchi’s optimization method with commercial electromagnetics software is introduced in the book. The proposed optimization method is used in various linear antenna arrays, microstrip filters, and ultra-wideband antenna designs. Successful examples include linear antenna array with a null controlled pattern, inear antenna array with a sector beam, linear antenna array with reduced side lobe levels, microstrip band stop filter, microstrip band pass filter, coplanar waveguide band stop filter, coplanar ultra-wide band antenna, and ultra-wide band antenna with band notch feature. Satisfactory results obtained from the design process demonstrate the validity and efficiency of the proposed Taguchi’s optimization method. Contents: Introduction / Orthagonal Arrays / Taguchi's Optimization Method / Linear Antenna Array Designs / Planar Filter Designs / Ultra-wide Band (UWB) Antenna Designs / OA-PSO Method / Conclusions

In this paper we intend to find out what resolution can be achieved with two-dimensional Angle of Arrival localization when using linear antenna arrays at 2.4 GHz. A theoretical resolution calculation method is presented. Room dimensions, number of cooperating anchor nodes (provided with a linear antenna array) which track the position of a mobile node and number of antenna elements can be chosen. These theoretical calculations lead to the definition of a reference value which can be used to calculate the expected resolution for all rectangular shaped rooms with the desired variable settings. It is also shown that square rooms result in the best resolution and adding extra antenna elements improves the resolution. The design and calibration of a practical linear antenna array, with four linearly positioned 2.4 GHz antenna elements and inter distance of λ/2, is presented. Measurements of practical beam patterns, and the corresponding −3dB beam widths, for different incident angles show that influences such as mutual coupling and reflections can not be neglected. The practical resolutions are compared with expected theoretical values and it is shown that besides I/Q and phase offset calibration, manifold calibration is necessary.

This paper proposes a novel high gain and low sidelobe level (SLL) linear microstrip array antenna for outdoor WLAN applications. The antenna consists of two main parts, which are a linear array and a reflector. The linear array comprises of 10 elements; those have been designed on Rogers RT/Duroid 5870tm with the dimensions of 422×100×10.15 mm3. To gain low SLLs, a series fed network was designed to have the output signals being proportional to the Chebyshev distributions (with preset SLL of -30 dB). Furthermore, Yagi antenna theory has been applied by adding directors above every single element to increase the directivity of the single element. The reflector has been constructed at the back of the proposed structure. Simulation results show that the array can provide high gain of 17.5 dBi and a low SLL of -26 dB. A prototype has been fabricated and measured. Good agreements between simulation and measurement data have been obtained.

The desired performance parameters of a specific linear antenna array (LAA) are a highly nonlinear function of input parameters such as antenna length (l) and spacing (d) among the antenna elements and need to be optimized to get all the desired performance parameters. This paper presents popular bio-motivated global optimization techniques such as particle swarm optimization (PSO) and cuckoo search (CS), which are being applied to LAA design to enhance directivity and low sidelobe level. A comparison between two optimization techniques has also been made. To analyze the antenna structure, a numerical method called method of moments has been used, and mutual coupling is taken into account between antenna elements. MATLAB is used for the design and optimization of LAA, and CST microwave studio is used to validate the results obtained. Finally, a graphical user interface-based toolbox is developed for the design and optimization of LAA in MATLAB and to reduce the complexity for a beginner.

This article details about the method of controlling Side-Lobe-Level (SLL) in the radiation pattern of mutually coupled symmetrical linear dipole antenna array in a proper direction. There are several conventional numerical and analytical methods to compensate the effect of mutual coupling, but to get better performance on linear dipole antenna arrays, an effective optimization technique is implemented; i.e.; Craziness based Particle Swarm Optimization (CRPSO). This technique provides solution for the nonlinear array factor equation which comprised of general n-dimensional components including current excitation of each antenna array element and inter-element spacing. In addition, analysis of comparative studies is discussed with the aid of calculating driving point impedance of antenna array for optimum inter-element spacing. An adequate amount of improvement in radiation pattern is achieved by reducing the unwanted SLL. Empirical study on the result is analyzed both quantitatively and qualitatively.

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 this study, a 77 GHz phased array antenna based on substrate-integrated waveguide (SIW) is proposed. The proposed phased array antenna includes two columns of transmitting (TX) linear antenna arrays and two rows of receiving (RX) linear antenna arrays, which form a rectangular ring distribution. These TX and RX antennas are vertically polarized cavity antennas fed by SIW slots. Simulation results show that the TX antennas and RX antennas have good phased scanning capabilities of ±30° in the elevation direction and ±45° in the azimuth direction at 75–81 GHz, respectively. In order to verify the performance of the proposed antenna, we excite each one of the TX and RX linear phased array antennas using two SIW power dividers and two WR12 waveguide ports. The measured bandwidths of the TX and RX antenna arrays with voltage standing wave ratio less than 2 are 14.5% from 73.7 to 85 GHz and 13.7% from 72.5 to 83.2 GHz, respectively. The measured boresight gains of the TX and RX antenna arrays at the operating frequency band are around 12 and 11.5 dBi, respectively.

An efficient technique for the synthesis of randomly spaced linear antenna (RSLA) array with constraints of spacing between the element and their amplitude excitation coefficient is presented in this paper. The main aim is to obtain best suitable arrangement of randomly spaced element with uniform amplitude excitation on the aperture of RSLA array corresponding to lowest possible peak side lobe level (PSLL). The determination of said arrangement is done by employing Particle Swarm Optimization (PSO) technique. The usefulness of proposed method is validated by considering an example of a 24-element linear array with random inter-element spacings between 0.5λ-1.5λ. This array is numerically studied and results are compared against the equally spaced linear antenna (ESLA) array and further with published articles with similar design cases. It is further aimed that the minimum distance among the elements does not have significant effect on the radiation pattern due to mutual coupling of adjacent elements. This is researched by conducting comprehensive electromagnetic (EM) simulation study with an M-shaped radiating patch element using CST microwave studio software. The EM simulation results of the proposed RSLA array are compared with those of numerical computed and published ones. The obtained results confirm that the proposed algorithm is able to attain better PSLL and valid to design RSLA arrays for practical applications.

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.

The thinning in the antenna array involves reducing the number of elements with desired sidelobe level (SLL) and beamwidth (BW). In this paper, the linear antenna array (LAA) is chosen for thinning with the objective of obtaining the suppressing the SLL to the best possible level with the constraint of fixed uniform BW. The considered LAA shall have 40 elements in the full array configuration in which all the elements are switched ON. Further, the LAA is thinned with different magnitudes while the elements to be switched OFF are determined as per the objective using the social group optimization algorithm (SGOA). The process of thinning is perceived as the non-uniform spacing technique of suppressing the SLL with constraints. The results are analyzed in terms of radiation pattern plots. The simulations are carried out in MATLAB.