A narrow-band ferroelectric tunable bandpass filter for K-band applications

The main objective of our research was to design, fabricate and test a narrow-band (<1% bandwidth) low-loss ferroelectric tunable bandpass filter (BPF) for integration into a gain-compensated down-converter targeted for the next generation of K-band satellite communication system. The BPF was designed using a conductor (gold or HTS)/ferroelectric/dielectric modified microstrip structure for a centre frequency of 19 GHz, a bandwidth of 150 MHz, and for a minimum frequency tunability of 10%. Several narrow band BPFs were fabricated and tested. Experimental results indicate higher losses in the BST ferroelectric based narrowband BPF compared to low temperature tunable STO based BPFs.