Frequency-invariant pattern synthesis for conformal array with space-time-polarization weighting

In this paper, a novel hybrid Invasive Weed Optimization (IWO) and Cuckoo Search (CS) algorithm (IWO/CS) is presented for phase-only pattern synthesis of large array antenna. The hybrid IWO/CS algorithm embeds the Levy flight of CS algorithm into IWO algorithm as a global guide, thereby enhancing the global search ability of the algorithm. At the same time, in order to avoid trapping into the local optimal solution, mutation operator is introduced to enhance search ability of the algorithm. Finally, competitive exclusion operation is improved to maintain the diversity of population. The hybrid algorithm is applied to phase-only beam shaping to achieve main lobe broadening and side lobe depression. Simulation results demonstrate the superiority of the hybrid IWO and CS algorithm.

본 논문에서는 2차 함수 곡선의 회전체 곡면 위에 있는 배열 안테나의 빔 합성을 위한 Enhanced Adaptive Genetic Algorithm(EAGA)을 제안하였다. 제안된 알고리즘은 더 빠른 수렴 속도와 더 낮은 비용함수 값을 얻기 위해 Adaptive Genetic Algorithm(AGA)과 Invasive Weed Optimization(IWO)을 결합시켰다. 각 안테나 소자의 급전 크기와 위상의 최적화된 값은 EAGA를 통해 구하였으며, 이 결과를 통해 EAGA가 컨포멀 배열 안테나의 패턴 합성 알고리즘으로써 AGA보다 더 우수함을 보였다. This paper proposes an enhanced adaptive genetic algorithm(EAGA) dedicated to pattern synthesis of array antenna which conforms to a curved surface of rotation with quadratic function. EAGA combines adaptive genetic algorithm(AGA) with invasive weed optimization(IWO) for the faster convergence and the lower cost value of the cost function. The amplitude and phase of each excited weighting factor are optimized to meet the required goals using EAGA. The EAGA results indicate that the proposed algorithm is superior to AGA when applied to the problem of conformal array antenna pattern synthesis.

A fast algorithm is given for computing the optimal weight vector in antenna array pattern synthesis having a set of null constraints. The algorithm requires only a UDUT decomposition of an m + 1 × m + 1 real positive definite matrix and the computation of the first row of the inverse of a triangular matrix of the same dimension, where m is the number of null constraints.

An efficient search technique based on a touring ant colony optimization algorithm is presented for the shaped-beam pattern synthesis of a linear antenna array. The element excitations of equally spaced array and the element positions of uniformly excited array are determined to closely approximate the desired pattern. In the touring ant colony optimization algorithm, the frequency memory feature of tabu search is used. Illustrative examples of cosecant, flat-topped and pencil beam patterns are given to verify the validity and accuracy of the technique.

In this paper synthesis of single ring non-uniform circular antenna for maximum side lobe level (SLL) reduction and improved first null beamwidth (FNBW) is dealt with. Evolution based Differential Evolution (DE) is used to determine an optimal set of current excitation weights and antenna inter-element spacing that provides optimal radiation pattern. Circular array antenna laying on x-y plane is assumed. DE is applied on circular arrays of 8-, 10-, and 12- elements. Various simulation results are presented and hence performances of SLL and FNBW are analyzed. Experimental results show considerable reductions of both the SLL and FNBW with respect to those of the uniform case and some standard algorithms GA [12], PSO [14] and SA [11] applied to the same problem of non-uniform circular antenna arrays.

In this article, we propose a deep neural network (DNN)for the radiation pattern synthesis of an antenna. The DNN utilizes the radiation patterns as inputs and the amplitude and phase of the antenna elements as outputs. Consequently, the radiation patterns of the array antenna can be easily obtained from the outputs of the trained DNN, which are amplitude and phase of the antenna elements. However, it is difficult to determine the amplitude and phase of each antenna element from the desired pattern in an environment where inter-element coupling exists. For this purpose, 6,859 radiation pattern samples for a 4×1 array patch antenna were generated by changing the phases of the antenna elements, and those patterns were leveraged to train the proposed DNN with low complexity. The radiation patterns of the ideal square and triangular array shapes, which are practically infeasible to implement, were used as inputs to the DNN. It was confirmed that the radiation pattern generated from the output signals of the DNN was very similar to the input radiation pattern.

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.

The work presents a design of a cylindrical conformal phased microstrip antenna array. Based on the HFM and the parallel feed network, a conformal microstrip 2 times 8 array on a cylinder surface is designed by the isotropic transformation theory (IT). Simulation results show that the conformal array works at 35GHz and the gain is 19.6dB at the center frequency. The phase-scanned patterns of the conformal 2 times 8 array are analyzed by the CST using phase control method. From the comparison of the scanning results at different phase division, it can be found that the scan angle, the angular width and the side lobe level varies following the trends of the phase division, at the same time, the gain of the conformal array changes markedly opposite the trends of the phase division. Therefore, this is a shortcoming of the conformal phased array. This kind of conformal phased sub-array can be easily expanded into a large-scale conformal array and be suitable for active integration with other microwave circuits and communication systems if this disadvantage was eliminated after further discussion in future.

A novel embedded element pattern decomposition method is proposed to synthesize conformal phased antenna arrays. This method decomposes the embedded element patterns as a product of a characteristic matrix and a Vandermonde structured matrix. This Vandermonde matrix is composed of modes in the modal space at the sampling angles. Because the fast Fourier transform (FFT) algorithm can be used in the Vandermonde structure, the computational cost can be reduced tremendously. In addition to its computational efficiency, the proposed method is also applicable to the synthesis of a pattern with any mainlobe direction and optimized polarization. A modified particle swarm optimization (PSO) method is applied to optimize the weights of the modes. This method is demonstrated through a simulation of a 9-element conformal array. The results show the advantages of the new method in achieving a low peak side lobe, accurate mainlobe scanning, and low cross-polarization.

<span>This work investigated a miniaturized slotted conformal antenna array for multiband application. Three guard lines are incorporated to the side of main patch and top of main patch to reduce surface current for planner surface and observe the effect of guard line due to which it resonate at three frequencies in X band and Ku band to be useful for multiband. A rectangular slot is etched at center of patches to increase the current path for wide band application. A quarter wavelength feeding network is used with good agreement of impedance matching. The main lobe width and direction shows through the radiation pattern which remains stable even it is significantly curved. This structure is wrapped around a cylinder with a diameter of 41.4 mm in the circumferential direction. It is observed that the planner antenna array operating at 8.4 GHz, 11.2 GHz &18.2 GHz with a return loss of -20 dB to -45 dB with fractional BW of 25% at 3rd frequency range and the directivity from 3.4 dBi-6.8 dBi. By doing some alteration in dimensions for the conformal antenna producing fractional BW of 20% and the directivity 5.5 to 9.1 dBi at resonating frequencies of 8.4 GHz, 11.4 GHz, and 17.5 GHz. This proposed array is simulated on CST software.</span>

The problem of radiation from sources in the presence of smooth convex objects is of great interest in the design of antennas on structures, e.g. conformal arrays. Conformal antenna arrays are required whenever on antenna has to conform geometrically to some shaped surface, like that of an aircraft. In the analysis of conformal antennas it is possible to obtain a modal solution to same canonical surfaces, e.g. a circular cylinder or an elliptic cylinder. But for more arbitrarily shaped bodies other methods have to be used. In this paper a hybrid method of UTD and MoM is used to analyse convex cylindrical structures. This method allows higher order modes to enter the calculations, thus receiving better agreement compared to known results. The UTD solution used is the one published by Pathak et al. (1981). The results from the hybrid method have been compared with measured results obtained from a cylindrical test antenna with 54 apertures built at Ericsson Microwave Systems AB in Molndal, Sweden. When higher order modes are included excellent agreement is obtained between measured and calculated results.

This paper presents studies on the design and development of conformal antennas placed on cylindrical curved surfaces. Conformal antenna array consists of 96x8 elements has been designed and a section of the array with 24 elements has been studied in terms of gain, beamwidth and Sidelobe level. The design has been carried out using MATLAB and the optimization has been carried out using 3D EM simulation software HFSS. The conformal array has been fabricated on RT Duroid substrate of thickness 20 mil and the measured results are presented along with simulated results.

A novel method for the synthesis of arrays in the presence of conducting scatterers is presented. This method includes and takes advantage of the radiation of the scatterer by using the generalised multipole technique. Thus, the optimum solution can be obtained for an array in the presence of a conducting obstacle.

The synthesis of array antennas mounted on ships, or any other vehicular platform, is addressed here. Both the mutual coupling between the array elements, and their interaction with the mounting platform, are considered and introduced into the synthesis procedure. This is done by using a three-dimensional formulation of the method of moments, which models the currents induced on the platform and the antennas, combined with an optimization procedure. Some results are presented, illustrating the capability of the proposed synthesis method.

The paper describes the synthesis of shaped-beam dual-reflector antenna patterns using two methods. In the first, for a prescribed far field the antenna aperture field is obtained initially and then a Geometric Optics synthesis method used to define the reflector coordinates. In the second method an optimisation procedure is employed to shape the reflectors directly, so as to generate, through Physical Optics, the desired far field. The two methods are compared for the pattern corresponding to the EUTELSAT 2 spacecraft. Close agreement is found and differences ascribed to initial constraints.