Miniaturized lumped-distributed narrowband ring filter design

A miniaturized narrowband bandpass filter with wide stopband is needed for communication application, therefore a microstrip inductive-compensated coupling-fed ring bandpass filter with a lumped lowpass filterd in loop resonator is proposed. Simple equations for filter design procedure are derived based on ideal transmission line model. To confirm the technique, a narrowband bandpass filter operated at 2.4 GHz with a 5% bandwidth and wide stopband is designed. Simulated and experimental results of the design are performed to validate the technique proposed.