VARIABLE MICROWAVE COLD/WARM NOISE SOURCE

摘要

A radiometer calibrating system (150) utilizes an adjustable noise source (100) for calibrating a radiometer. The noise source includes a transistor configured as a noise equivalent circuit having a gate port, drain port and source port. A source inductance providing series feedback for the noise source has one end coupled to the source port of the noise equivalent circuit and another end connected to the ground. A bias circuit controls the amount of DC bias applied to the noise equivalen t circuit. In order to match the impedances in the noise source, an output impedance matching network is connected to the gate port of the noise equivalent circuit. The output and input impedance networks have an output port and input port, respectively. Included in the noise sour ce is a port switch that terminates a matched load to the output port when a cold thermal radiation temperature is generated at the input por t, and alternatively, the port switch terminates the matched load to the input port when the warm thermal radiation temperature is generated a t the output port.