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To minimize the peak sidelobe level (PSLL) of sparse concentric ring arrays, this paper presents an optimization method of grid ring radii of these arrays. The proposed method is based on modified real genetic algorithm (MGA); it makes grid ring radii as optimal variables and makes elements more reasonably distributed on the array aperture. Also, it can improve the PSLL of the sparse concentric ring arrays and can meanwhile control the computational cost. The simulated results confirming the efficiency and the robustness of the algorithm are provided at last.

A novel and compact dual-mode wideband bandpass filter (BPF) with multiple transmission zeros is designed, fabricated, and measured in this paper. This filter consists of a modified right-triangle patch resonator with two orthogonal narrow-strip stubs and improved input/output defected microstrip structure (DMS). The designed resonator and DMS show dual-mode and dual-bandgap characteristics, respectively. The equivalent circuit models are described and their element values are also extracted by the full-wave EM simulator. The presented BPF is constructed by cascading the stub of patch resonator with the input/output DMS and overlapping partly with each other between the stub of resonator and middle conductor strip of input/output DMS. The EM simulated result has been confirmed by an experimental one and they have shown good agreement with each other. The measured result exhibits wide passband and low insertion loss characteristics for the proposed filter. IntroductionWith the rapid development of modern mobile communication systems, the miniaturized, low-cost, and wideband filters with lower insertion loss and higher frequency selectivity have been increasing demands in many wireless applications. Among these filters, dual-mode resonator filters have been widely used for their compact size.[1-7] The microstrip dual-mode triangular patch resonators and their applications for dual-mode filters with less than 10% 3-dB fractional bandwidth (FBW) have been investigated in [1]. A dual-mode bandpass filter (BPF) with 3-dB FBW of 16% using a pair of spur-line resonators has been reported in [2]. A single-slotted circular patch resonator has been used to design a dual-mode dual-band BPF, which has a 3-dB FBW of less than 10% in any passband.[3] A BPF based on E-shaped dual-mode resonator has been designed and implemented, which has a FBW of 2%.[4] In [5], a dual-mode half wavelength resonator filter with centrally loaded open stub and quasi-L-shaped feed-lines has been reported, which has a narrow FBW of 4.7% at the central frequency. A fourth-order dual-mode microstrip BPF with a FBW of 11% has been developed in [6]. In general, the insertion losses of above-mentioned filters are greater than 1.0 dB within their passbands. A coupled-line BPF using dual-mode half-wavelength SIR centrally loaded with shorted stub has been studied in [7], which has a suppression characteristic for high-order harmonics, however, the dual-mode filter still has a narrow bandwidth and high insertion