Design method for bandpass filter with enhanced stopband rejection using spiral SIRs

Abstract

A new design method for a compact narrowband bandpass filter with high out-of-band rejection level is presented. A cross-coupled spiral stepped-impedance resonator (SIR) filter is proposed which consists of four spiral SIRs to realise the sharpest skirt characteristic. The fundamental mode is strengthened while spurious modes are suppressed, so the proposed filter rejects 4.79 dB more on average than the conventional filter. The loaded Q is 59.36.