An Open-Loop Technique for the Stabilization of Microwave Sources

Abstract

An open-loop technique is evolved to temperature compensate the voltage-controlled oscillators used in the microwave systems. The mathematical background along with empirical analysis and design details is presented. Compensation of the frequency change is accomplished by changing the capacitance of the varactor through the application of a temperature dependent voltage across the varactor and this change in the frequency of the resonator is equal and opposite in sense to the change caused by temperature. This technique has advantages over the modern PLL technique from the point of view of cost, modulation and the simplicity of design. Using this approach, an improvement in temperature stability of 2 GHz source from ±1000 ppm to about ± 50 ppm over 0 to 50°C has been achieved.