A Tunable X-Band Band-Pass Filter Module Using YIG/GGG Layer on RT/Duroid Substrate

A tunable X-band band-pass filter (BPF) module that consists of an 8-12-GHz passive BPF and a pair of tunable band-stop filters (BSFs) using yttrium iron garnet/gadolinium gallium garnet (YIG/GGG) layers on RT/Duroid substrate is reported. The passive BPF and the tunable BSFs were first designed, simulated, and optimized using AWR Microwave Office Simulator. The tunable X-band BPF module was then constructed and simulated under 2-D bias magnetic fields with Ansoft HFSS software suite. The measured passband of the passive BPF was 7.8-11.8 GHz, with the center frequency at 9.8 GHz and the 3-dB bandwidth of 4.8 GHz. With the sets of bias magnetic fields at 1,700 and 2,360 Oe; 2,570 and 3,180 Oe; and 1,725 and 3,180 Oe applied on the pair of BSFs, tuning for the passband of the BPF module toward the high end, the low end, and the center was accomplished with the center frequency at 11.5, 7.9 and 9.8 GHz, the 3-dB bandwidths of 1.0, 1.1, and 1.2 GHz, and the tuning ranges of 3.4, 4.0, and 3.6 GHz, respectively. A good agreement between the simulation and experimental results was achieved.