Noise-Synthesis Technique in Time~Domain for Metrology Application
Dazhen Gu, Jeffrey E. Jenkins
We developed a prototype radiometer system to implement the noise-synthesis technique. A solid- state switch synthesizes noise signals from outputs of two synchronized electromechanical switches. The input ports of electromechanical 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 solid-state 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. We accomplished highly efficient measurements of the noise temperature with the improved precision. The uncertainty due to non-identical input- impedance states is also properly accounted for. Several future works are suggested to further improve the system performance.
IEEE Transactions on Instrumentation and Measurement