It seems that in last few years the quartz crystal precision oscillators OCXO did reach the limit of parameters improvement. Most of OCXO designers focused their attention on price reduction and practicability of oscillator construction. In Tele and Radio Research Institute new designs of OCXO oscillators fulfilling requirements of military standard MIL-STD-202G were made. In the paper there are described important requirements for military and civil OCXO oscillators and parameters of new designed oscillators. The results of new elaborated oscillators investigations show that the improvement of OCXO oscillators parameters is still possible.

The modern OCXO quartz oscillators requirements and parameters

Due to the constant temperature oven, the OCXO can have a higher frequency stability in both long-term and short-term comparing to other crystal oscillators. However, most of OCXOs are using passive temperature control components, such as heating resistors or power transistors, which makes OCXOs have long warm-up time and ease to be affected by the ambient temperature fluctuation. In this paper, demonstration of using the thermoelectric cooler as the temperature control for the OCXO has been studied. Simulation results show good consistence with the test results for using the TEC for the OCXO. Temperature control test results demonstrate the feasibility of using the TEC to control the temperature of the OCXO to improve the warm-up time and have better temperature stability.

Simulation and demonstration for the thermoelectric cooler to improve warm-up time of OCXO

Wysokostabilne rezonatory kwarcowe cięcia SC - konstrukcja i technologia

The timebase inaccuracy of an Analog-to-Digital Converter (ADC) is an important systemic error to consider when it comes to fast and precise mains frequency measurement. In this paper, a new calibration method to determine the timebase offset of an ADC in real time to correct the mains frequency measurement is proposed and evaluated in tests. The methods uncertainty with regard to different calibration signal frequencies is assessed.

Timebase Offset Calibration of Analog-To-Digital Converters for Mains Frequency Measurement

Warm-up time, which is for the OCXOs to get the nominal frequency stability, is a critical factor for the application of OCXOs. In most OCXOs, the temperature sensing and control method is passive involving heating resistors or power transistors. This kind of configuration makes the normal warm-up time around/above 3 minutes, which is not suitable for the applications requiring quick start and test scenarios. In order to improve the warm-up time, this paper presents a new active temperature sensing and control method by employing a thermoelectric cooler (TEC) to shorten the warm-up time. Test results show the warm-up time could be less than 1 minute and the temperature stability of the OCXO with the TEC is better than the one without the TEC.

Temperature sensing and control to improve warm-up time of OCXOs

The main mode lateral field excited resonators exhibit high value of motional resistance and very low value of motional capacitance. One undesirable property of these resonators is difficult frequency calibration and oscillator frequency adjustment. The anharmonic mode resonators exhibit lower motional resistance and few times higher motional capacitance. Because of that frequency calibration and frequency adjustment in oscillator is significantly easier. Different versions of SC 301 and 310 mode resonators have been designed and elaborated over past several years. The results were optimized practically versions of 301 and 311 mode resonators. For lateral field excited resonators the double oven OCXO oscillator was designed. The resonators were mounted in oscillators. Next the short term stability, long term stability and thermal stability of oscillators were measured, using conventional methods of measurement. The long term frequency stability measurements were carried out in laboratory with ambient temperature stabilization in the range 20plusmn1degC. The oscillators exhibited long term frequency stability below 2 E-11 per day and short term frequency stability below 2 E-13 per second. The analysis of the oscillator parameters measurement showed main influence on them not resonator quality but the oscillator construction and utilized electronic components quality. The result of analysis of these parameters was the new design of hermetically sealed oscillator with carefully selected electronic component. The oscillators were hermetically sealed for prevent of environmental conditions

K. Weiss

Papers

The modern OCXO quartz oscillators requirements and parameters

High stability quartz oscillators utilizing anharmonic mode LFE resonators

Wysokostabilne generatory kwarcowe z rezonatorami anharmonicznymi pobudzanymi polem równoległym