Synthesis Trisection Filter with Improved Quasi-Elliptic Passband Flatness

摘要

Synchronously tuned stepped-impedance resonators (SIRs) are used to synthesize a trisection bandpass filter with adequate frequency-dependent cross coupling so that a quasi-elliptic function passband can be achieved. The measured response, however, shows a rounding passband due to finite Q microstrip resonators. Two lossy detuned resonators are then inserted in shunt to improve the passband flatness. Coupling matrix approach is used for circuit synthesis. An experimental filter is fabricated and measured, and its responses show good agreement with the simulation.