Design of continuously tunable superconducting filter with semiconductor varactors

Abstract

This article presents a four-pole continuously tunable high-temperature superconducting combline filter at L band on MgO substrate. Gallium Arsenide varactors are used as tuning elements in the filter. Additional varactors are used to tune the external quality factor of the input and output couplings. A shorted U-shape secondary coupling line is introduced to match the desired couplings so as to maintain a good return loss in the entire tuning range. The four-pole filter achieves a tuning range of 11.5% from 983.85 to 1103.6 MHz. The insertion loss is 0.46 dB at 1103.6 MHz with the bias of 9 V. The unloaded quality factor of the resonators in the four-pole filter is estimated to be 710 at 1077.6 MHz.

A High-Temperature Superconducting Bandpass Dual-Mode Filter with Tunable Relative Bandwidth and Center Frequency

“…Filters with microwave tenability are crucial for WCSs both presently and in the future. Semiconductor varactors have been widely used in developing tunable filters owing to their cost effectiveness, high tuning speed, and miniaturized size [ 8 , 9 , 10 , 11 ]. High-temperature superconducting (HTS) filters that are characterized by reduced insertion loss, steep band edge, and increased out-of-band rejection are promising for these applications [ 12 ].…”