Microstrip Cross-coupled Interdigital SIR Based Bandpass Filter

A simple and compact 4.9 GHz bandpass filter for C-band applications is proposed. This paper presents a novel microstrip cross-coupled interdigital half-wave- length stepped impedance resonator (SIR) based bandpass filter (BPF).The designed structure is similar to that of a combination of two parallel interdigital capacitors. The scattering parameters of the structure are measured using vector network analyzer (VNA). The self-generated capaci- tive and inductive reactances within the interdigital reso- nators exhibited in a resonance frequency of 4.9 GHz. The resonant frequency and bandwidth of the capacitive cross- coupled resonator is directly optimized from the physical arrangement of the resonators. The measured insertion loss (S21) and return loss (S11) were 0.3 dB and 28 dB, respec- tively, at resonance frequency which were almost close to the simulation results.