A simple method of removing receiver noise from microwave noise measurements

A simple method is introduced by which, during measurements of noise figure and gain, the output reflection coefficient of the device under test can be adjusted to some constant value without the use of a network analyser, thereby keeping the noise figure of the noise measurement system constant. This removes an important source of error in noise figure and noise parameter measurements. A circulator and tuning network (e.g. a three-stub tuner) are used, but there is no need for the circulator to be tuned for perfect circulation. In an experimental test to verify the accuracy of the method, excess noise temperatures and available gains of a two-port were measured for a wide range of values of the complex reflection coefficient of the noise source and compared against values calculated from the measured scattering parameters of the same two-port.