Noise Comparators and Standards for S and X Bands

Noise comparators and associated thermal standards have been developed to provide accurate noise source calibration facilities at S and X Bands. The comparators are based on a null-balance form of the Dicke radiometer, but eliminate problems of RF switching by using an IF switch. Matching facilities are incorporated. The thermal standards include both waveguide and coaxial forms and operate at 400°C. The most successful type is described in detail. Gas discharge noise sources have been developed as highly reproducible transfer standards, with outputs stable over many thousands of hours to within a few hundredths of a decibel.