Temperature Performance Measurement Methods for Temperature-Compensated Quartz Oscillators

摘要

Extensive temperature performance measurements associated with temperature-compensated quartz oscillators (TCXO's) have led to the need for automatic test methods. Manually operated and attended measurements, when applied to the TCXO, become grossly inefficient. Also, the high degree of nonlinearity of the TCXO frequency-temperature characteristic and long and unequal/thermal time constants of TCXO components place greater demands on accurate frequency-temperature (F-T) stability determination than are normal for wide temperature range, non-oven controlled quartz oscillators. This report considers the steady-state and transient temperature behavior of TCXO's in a test environment and its relationship to temperature performance measurement errors. A common occurring nonlinearity and end point temperature slope of the F-T characteristic establish a maximum measurement temperature interval and minimum end point measurement temperature accuracy. Mathematical approximations of the thermal response of frequency determining TCXO components to step air temperature changes permit relating measurement error to the time of measurement. Then, maximum frequency-temperature coefficients and transient temperature differences between crystal and compensation network thermistors can be employed to estimate stabilization time under worst case conditions. Two methods applicable to an automatic measurement system, the sequential and continuous scan methods, are described and measurement error curves are plotted which permit the selection of either sequencing or scan rate for a specific TCXO design. (Author)