Dual-mode oscillators for clocks and sensors

Frequency can be measured with far higher accuracy than any other quantity. Dual mode excitation of resonators allows the highly accurate measurement of, and compensation for, the effects of temperature, pressure, etc., by means of frequency measurements alone. In dual mode excitation, the two excited modes occupy the same volume of quartz, thereby eliminating gradients between the resonator and sensor. This paper reviews the dual-mode technique and its applications in oscillators, clocks and sensors.