Abstract: The present invention provides a wideband frequency tunable ring resonator, wherein, comprises a closed ?g/2 transmission line and two variable capacitors with tunable capacitance, the ?g/2 transmission line is axisymmetric around a central line, first ends of the two variable capacitors are respectively connected to two intersection points of the ?g/2 transmission line and the central line, the second ends of the two variable capacitors are respectively grounded. By implementing the technical solution of present invention, following technical effects are obtained. The fundamental resonant frequency (ffund) can be shifted up and down by controlling the respective values of the two loading capacitors, resulting in a bi-directional tuning of ffund. As a result, the tuning range of this invention can be approximately doubled as compared with the conventional tunable ring resonator.

Abstract: A microwave frequency tunable filtering balun is provided. The microwave frequency tunable filtering balun comprises a first microwave split ring transmission line resonator and a second microwave split ring transmission line resonator arranged in a bilaterally symmetrical manner, a fourth variable capacitor and a fifth variable capacitor of same parameters. It combines two functions of balun and tunable bandpass filter (BPF) into one circuit, resulting in a compact design. The balun characteristic and frequency-tuning mechanism are investigated, and the design equations are derived.

Abstract: A microwave frequency tunable filtering balun is provided. The microwave frequency tunable filtering balun comprises a first microwave split ring transmission line resonator and a second microwave split ring transmission line resonator arranged in a bilaterally symmetrical manner, a fourth variable capacitor and a fifth variable capacitor of same parameters. It combines two functions of balun and tunable bandpass filter (BPF) into one circuit, resulting in a compact design. The balun characteristic and frequency-tuning mechanism are investigated, and the design equations are derived.

Abstract: The present invention provides a wideband frequency tunable ring resonator, wherein, comprises a closed ?g/2 transmission line and two variable capacitors with tunable capacitance, the ?g/2 transmission line is axisymmetric around a central line, first ends of the two variable capacitors are respectively connected to two intersection points of the ?g/2 transmission line and the central line, the second ends of the two variable capacitors are respectively grounded. By implementing the technical solution of present invention, following technical effects are obtained. The fundamental resonant frequency (ffund) can be shifted up and down by controlling the respective values of the two loading capacitors, resulting in a bi-directional tuning of ffund. As a result, the tuning range of this invention can be approximately doubled as compared with the conventional tunable ring resonator.