Low Insertion-Loss and Sharp-Rejection Bandpass Filter Based on Bandstop Characteristics

A low loss and good inband performance of bandpass filter based on bandstop characteristics are introduced to demonstrate the small square loop filter structure. A bandpass filter is constructed by putting a pair of meander-stepped impedance inner corners along with either of the diagonal of the loop resonator. A proposed low loss and high rejection bandpass filter structure operate at 3.5 GHz, with 750 MHz bandwidth and 0.11 dB insertion loss. The shape factor can calculate the sharp rejection filter response is 1.87:1 at 30/3 dB bandwidth.