Gaseous Discharge Super-High-Frequency Noise Sources

The positive column of an electrical discharge through argon it utilized as a source of random fluctuations to provide a standard noise source for microwave frequencies. It is shown that the waveguide may be matched to the discharge with very low reflection over the entire recommended transmission bandwidth of the waveguide without the utilization of tuned elements. Further, when the discharge is not excited, microwave transmission through the guide is possible with very low reflection. The noise temperature is about 15.5 db above 290° K. Performance data are given for frequencies between 2,600 and 26,000 mc per second. The effect of varying the discharge parameters, geometry, gas, gas pressure and current, upon both the radio-frequency and noise performance is discussed. The factors affecting the occurrence of low-frequency fluctuations in the discharge are considered and the proper operating conditions to avoid their effects on the microwave performance are given. The hypothesis that the noise temperature corresponds to the electron temperature of the positive column is presented and supporting evidence is offered.