Low noise UHF BAW quartz resonator and oscillator.

摘要

In today's market, there is a high demand for low noise UHF resonators and filters. In this work, low noise BAW thickness shear quartz resonator is designed to work at UHF band by reducing its thickness. Oscillators built with these resonators showed excellent short term stability under vibration. A novel resonator called the ring electrode resonator was also designed and analyzed and its computational results are presented.; Three BAW resonators and one SAW resonator, all in the 300MHz range, are considered in this work. The BAW resonator sits on a 5mum thick cantilever quartz plate of 490mum by 500mu m, extending out from the base. Circular electrodes of 300mu m in diameter are plated on top and bottom surfaces of the quartz plate. Measurements have shown the fundamental thickness shear mode of a 320MHz BAW resonator has a Q of 13,000, 30% better than an off the shelf SAW resonator.; Oscillators using these four resonators as the frequency determining element were designed using two approaches, the negative resistance and the voltage/current ratios, and their prototypes were built and tested. Parametric studies were performed on them and their results showed that non ideal behavior of the components used in making the oscillator can have significant influence on the loop gain. To address this issue, loop gain analysis based on the negative resistance approach was extended to include the measurement data. By including the measurement data, accuracy of the analysis vastly improves.; The phase noise of the oscillators was measured under vibration free environment as well as under harmonic and aircraft vibration. Phase noise level under the quiescent condition for all oscillators are comparable. However under vibrating condition, the BAW oscillators performed significantly better than the SAW oscillator. The conjecture is that the resonator performance under vibration is correlated to the resonator design and the mode of operation.