Design of a low pass filter using rhombus-shaped resonators with an analytical LC equivalent circuit

Abstract

In this paper, a new method is presented for the design of a low pass filter (LPF) based on an LC equivalent circuit. Firstly, new formulas are proposed to calculate an LC equivalent circuit of a rhombus-shaped resonator. Secondly, the transfer function and transmission zero of the rhombus-shaped resonator are extracted, based on the presented formulas. Then other rhombus-shaped resonators are designed, based on the extracted formulas. The proposed filter has a cut-off frequency with an attenuation level of 3 dB at 1.54 GHz. The obtained return loss and insertion loss in the pass band are 16 dB and 0.1 dB, respectively. The designed filter is fabricated on RT-5880 with 31 mil thickness.