Frequency temperature behavior and its hysteresis of S-TCXOs using new shape GT cut quartz crystal resonators

Frequency temperature behavior and hysteresis of self-temperature compensated crystal oscillators (S-TCXOs) using cut quartz crystal resonators are described. A S-TCXO is successfully obtained with frequency deviation of +30/-150 ppb over a wide temperature range of -30 to +85°C, without any external temperature compensation. The thermal hysteresis of S-TCXOs is extremely small for the excursion of fall-temperature to rise-temperature, but occurs somewhat for the excursion of rise-temperature to fall-temperature. The variation quantity for each S-TCXO is less than 0.38 ppm in frequency deviation for the temperature excursion of -45 to +90 and -45°C. Aging quantity after pre-aging for about two weeks is found to be 0.3 ppm at a mean value of eight samples for one year and two months