MHz HTS Lumped Element Bandpass Filter

A 5-pole lumped element bandpass filter (BPF) of center frequency 264.05 MHz and fractional bandwidth (FBW) 0.76% is designed and fabricated using YBa 2 Cu 3 O 7-d (YBCO) thin films deposited on both sides of a MgO substrate(40 mm × 40 mm × 0.5 mm). The return loss, minimum insertion loss and ripple were measured to be 20.0 dB, less than 0.1 dB and less than 0.1 dB at 70 K, respectively. These results verify both the compactness and low loss characteristics in the VHF band. The simulated frequency response, where the frequency dependences of inductance (L) and capacitance (C) elements and housing effect are taken into account, is in good agreement with the measured frequency response. key words: high-temperature superconductor, microstrip line, lumped element circuit, bandpass filter