Realization of ultra-high quality factor of dual-T quartz crystal resonator circuit

In this paper, we have shown the method to obtain the ultra-high quality factor of a dual-T crystal resonator circuit. In this circuit, the phase shifters are inserted in each T circuit of the dual-T crystal resonator circuit. We have made the simulation and measurement of the proposed dual-T crystal circuit. The attained effective Q is about three times bigger than the unloaded Q of a crystal resonator (about 140,000). And we have made the oscillator using this dual-T circuit and made the simulation of phase noise. 30 through 60 dB improvement of phase noise is suggested in 1/f offset frequency region. The measurement shows the comparable phase noise improvement.