Design of Tunable Band-pass Filters and Phase Shifters Using BST Thin Film

In this paper, the band-pass filters (BPFs) and phase shifters using BST thin film are presented. Filters are consisted of Microstrip, Coplanar Waveguide (CPW), and conductor backed CPW (CBCPW) structures and phase shifters are consisted of CPW line and CPW with slit structures to improve phase shift effect. From the measurement results, the Microstrip, CPW, and CBCPW bandpass filters show the center frequencies of 6.61 GHz, 6.31 GHz, and 6.21 GHz with the insertion losses of 7.33 dB, 5.83 dB, and 6.83 dB, respectively at the bias voltage of 40 V. The tuning range for the bandpass filters is determined as 3%~8%. From the experiments, the CPW line and the CPW with slit phase shifters show the insertion losses of 1.9 dB and 2.4 dB at the bias voltage of 30 and the phase shifts of 9.8° and 10.6° at 16 ~ 18 GHz, respectively.