433 MHz wide-tunable high Q SAW oscillator

In this paper, we have made a 433 MHz dual-T SAW oscillator. The oscillator is made of an amplifier, variable gain amplifiers, phase shifters and dual-T SAW resonator circuit. Oscillation frequency can be changed by controlling the gains of variable gain amplifiers. The effective quality factor of the oscillator is enhanced by adjusting phase shifts of phase shifters. Frequency tunable range is about 1,200 ppm, exceeding the limit restricted by used SAW resonators. The effective quality factor of the oscillator is about 30,000, about three times of the unloaded Q of SAW resonators. Phase noise of the oscillator is estimated from the measured spectrum. Above 6 dB improvement of phase noise is obtained at 1kHz offset frequency compared to that of a colpitts oscillator.