In this article, in order to solve the problem of linear array synthesis with upper and lower bounds and aperture constraints, the improved bat algorithm (IBA) is proposed. The IBA embeds an adaptive local search strategy to enhance population diversity. Compared with other algorithms in antenna sidelobe suppression simulation, the bat algorithm has higher accuracy and effectiveness, and does not need to adjust too many parameters. K E Y W O R D S constrained optimization problem, improved bat algorithm, linear antenna arrays, sidelobe level, sparse arrays

Peak sidelobe level reduction (PSLR) is crucial in the application of large-scale array antenna, which directly determines the radiation performance of array antenna. We study the PSLR of subarray level aperiodic arrays and propose three array structures: dislocated subarrays with uniform elements (DSUE), uniform subarrays with random elements (USRE), dislocated subarrays with random elements (DSRE). To optimize the dislocation position of subarrays and random position of elements, the improved Bat algorithm (IBA) is applied. To draw the comparison of PSLR effect among these three array structures, we take three size of array antennas from small to large as examples to simulate and calculate the redundancy and peak sidelobe level (PSLL) of them. The results show that DSRE is the optimal array structure by analyzing the dislocation distance of subarray, scanning angle and applicable frequency. The proposed design method is a universal and scalable method, which is of great application value to the design of large-scale aperiodic array antenna.INDEX TERMS Subarray level aperiodic array, peak sidelobe level reduction, bat algorithm, redundancy.

A novel Fabry-Perot resonator antenna using a double-layer partially reflective surface (PRS) to enhance the operating bandwidth is proposed. Two layers of double-sided printed substrate are employed as the PRSs. A higher-permittivity dielectric substrate is inserted between the two PRSs to produce a positive reflection phase gradient, which is essential to expand the bandwidth. A wideband aperture-coupled microstrip antenna is utilized as the feed antenna to further improve the working bandwidth. A prototype of the proposed antenna is fabricated and tested to validate the simulated results. The experimental results show that the designed antenna has a wide impedance bandwidth ( S 11 j j< À 10 dB) of 9.43-13.0 GHz (35.7%) with a 3-dB gain bandwidth ranging from 9.12 to 12.26 GHz (31.4%) and a peak gain of 15.4 dBi at 10 GHz.

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