Noise Synthesis Technique in Time Domain for Metrology Application

Abstract

We developed a prototype radiometer system to implement a time-domain noise synthesis technique. A solid-state (SS) switch synthesizes noise signals from the outputs of two synchronized electromechanical (EM) switches. The input ports of EM switches are terminated by one unknown noise source, one known cold noise reference, and two known ambient noise references. The magnitude of the synthesized noise signals can be varied by the duty cycle of the transistor–transistor logic (TTL) pulse that controls the SS switch. By regulating the TTL pulse, a null balance is reached when the power level of the synthesized noise signals equal to that of the ambient noise reference. The noise synthesis radiometer represents a major step forward over the conventional noise-injection radiometer, enabling highly efficient measurements of the noise temperature with improved precision. The uncertainty due to nonidentical input-impedance states is also properly accounted for. Several future works are suggested to further improve the system performance.