Compact Wide-Band and Narrow-Band Microstrip Bandpass Filters Using the LC Equivalent Model

This paper presents an improved design methodology for developing two types of microstrip bandpass filters, a narrowband filter and a wideband filter, employing stepped-impedance resonators (SIRs) and parallel stubs. The fundamental resonator integrates two parallel stubs and a centrally located air gap within a stepped-impedance structure. The corresponding even- and odd-mode capacitances are evaluated, and an additional SIR is coupled to the primary resonator to achieve the desired bandpass response through dimensional optimization. To verify the electromagnetic simulation results, an equivalent LC circuit model is extracted and analyzed, demonstrating strong agreement with the full-wave response. Owing to its compact geometry and structurally efficient configuration, the proposed filter is well suited for integrated microwave systems. The wideband implementation is designed to operate at a center frequency of ۱۰.۰۲ GHz, exhibiting an insertion loss of ۱.۰۳ dB, a return loss of ۳۰.۱ dB, and ۱.۳۳ GHz bandwidth. In contrast, the narrowband design achieves a center frequency of ۲.۴ GHz with an insertion loss of ۰.۱۵ dB, a return loss of ۲۶.۲۶ dB, and ۱۰۲ MHz bandwidth.

کلیدواژه ها:

Microstrip bandpass filter ، Narrowband Filter ، Stepped-impedance resonators (SIRs) ، Wideband Filter