High-efficiency piezoelectric-transducer-tuned feedback microstrip ring-resonator oscillators operating at high resonant frequencies

A tunable-feedback ring-resonator oscillator using a voltage-controlled piezoelectric transducer (PET) is introduced. The new oscillator is constructed by a ring resonator with a pair of orthogonal feed lines as a feedback structure. The ring resonator with two orthogonal feed lines can suppress odd modes and operate at even modes. This operation shows a similar characteristic of high operating oscillation frequencies as that of the push-push oscillators. The high operating resonant frequency characteristic is predicted by a simple transmission-line model. The simulated and measured results agree well with each other. At a fixed frequency of 12.09 GHz, the oscillator has a high DC-to-RF efficiency of 48.7% with an output power of 5.33 dBm. A voltage-controlled PET is used to vary the resonant frequencies of the ring resonator, which, in turn, tunes the oscillator with a good tuning rage of 4.25% around 12 GHz. This tuned oscillator operating at high oscillation frequency can be used in many wireless and sensor systems.