Double temperature compensated crystal oscillator

This paper introduces a double temperature compensated TCXO which combines two different compensation techniques. The crystal oscillator is compensated with an analogue approach firstly, then compensated secondly with a digital approach based on an improved frequency temperature performance. According to the frequency temperature characteristics of the VCTCXO, a microprocessor generates the secondary compensation voltage after processing. With the voltage as the control signal to the VCTCXO, the frequency-temperature stability of the crystal oscillator can be compensated into ±2∼3×10^-7 in a -55°C to +90°C temperature range. Utilizing this method, the demand on the secondary compensation is decreased noticeably and the structure can be very simple. The temperature compensated crystal oscillator, based on the double compensation, is of low cost and shows less susceptibility to power supply instability and has better reliability. Compared with ordinary DTCXO and MCXO, based on AT cut crystals, it is easier to produce.