Design of low phase-noise voltage-controlled oscillator using tunable evanescent-mode cavity

In this paper, a low phase-noise voltage-controlled oscillator using tunable evanescent-mode cavity is designed, fabricated, and measured. The oscillator is tuned by lumped element varactors placed on the top surface of a substrate-integrated evanescent-mode cavity. The tuning range of the oscillator is 783.6-976.8 MHz with peak output power of 6.97 dBm at 943.2 MHz. Over the tuning frequency the oscillator has a phase noise from -103.8 to -119.4 dBc/Hz at 100 kHz offset frequency and from -141.8 to -152.3 dBc/Hz at 1 MHz offset frequency. The resonator is compatible with RF MEMS tuner to yield a higher resonator Q and better phase noise performance.