Compact cascade quadruplet bandpass filter with extend rejection bandwidth

Abstract

This paper proposes a compact bandpass filter with excellent out-of-band performance. Stepped-impedance resonators (SIRs) are used to achieve an extended rejection bandwidth. Loaded stubs are also introduced to suppress the harmonic responses. The SIRs and the loaded stubs take up little extra room, and thus the proposed filter has a compact size. In this paper, a bandpass filter centered at 2 GHz is presented, with 20 dB rejection level up to about 16 GHz.