An Active Cold and Hot Noise Generator

An active cold and hot noise source is designed based on a low noise amplifier (LNA) and a single pole double throw (SPDT) switch with load. It is often easy to make a LNA's reverse noise temperature lower than the ambient temperature, while the forward noise temperature is higher than the ambient temperature. The cold and hot noise temperature output is achieved by changing the status of the SPDT switch. At the same time, an attenuator is used to adjust the output of the forward noise power to achieve multi hot noise temperature points output. The cold noise temperature of about 110 K and hot noise temperature range from 300 K to 15000 K are obtained by a commercial LNA in the frequency band of 4 GHz to 8 GHz.