Low Loss Tunable Superconducting Dual-Mode Filter at L-Band Using Semiconductor Varactors

• Published in: IEEE microwave and wireless components letters 2014-03, Vol.24 (3), p.170-172
• Main Authors: Suo, Guannan, Guo, Xubo, Cao, Bisong, Wei, Bin, Zhang, Xiaoping, Shang, Zhaojiang, Zhang, Guoyong
• Format: Article
• Language: English
• Subjects: Applied sciences; Bandpass filter (BPF); Bias; Circuit properties; Couplings; dual-mode resonator; Electric potential; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; Frequency filters; Gallium arsenide; high-temperature superconducting (HTS); High-temperature superconductors; Joining; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Microwave filters; Oscillators, resonators, synthetizers; Resonators; Semiconductors; Superconducting filters; Superconductivity; tunable; Tuning; varactor; Varactors; Voltage
• ISSN: 1531-1309; 2771-957X; 1558-1764; 2771-9588
• DOI: 10.1109/LMWC.2013.2293667

This letter presents a superconducting continuously tunable bandpass filter with dual-mode resonator and Gallium arsenide (GaAs) varactors. The even- and odd-modes of the dual-mode resonator can be tuned simultaneously using a single bias voltage. The interstage and external couplings are realized with interdigital coupling structure to enhance the coupling strength. A four-pole dual-mode superconducting filter at L-band with a fractional bandwidth of approximately 20% is successfully designed. Two transmission zeros are generated in the upper stopband to increase the stopband rejection. The tuning range of the filter is 16% from 784.92 to 918.23 MHz. The insertion loss at 918.23 MHz is 0.69 dB with a reverse bias voltage of 9 V. The measurements of the filter match well with the simulated ones.