Summary of Measurement Techniques of Para-Metric Amplifier and Mixer Noise Figure

Expressions are derived for the noise factor of a frequency mixing circuit under two different operating conditions: 1) single-sideband operation with input only in a band of frequencies at omega₁; and 2) double-sideband radiometer operation with incoherent inputs in the bands both at frequency omega₁ and at omega₂=omega₃-omega₁. In both cases, the output is taken only at omega₁. It is shown that the noise figure for radiometer double-sideband operation is not always 3 db less than for single-sideband operation. It is also shown that it is possible to obtain an output signal-to-noise ratio which is greater than the input signal-to-noise ratio for coherent double-sideband operation. Methods are analyzed for measuring the effective noise temperature of this circuit by using a broad-band noise source.