一、前言近年来,微波低噪声器件的发展十分迅速。低噪声的混频器、晶体管放大器和参量放大器等已被广泛地应用于雷达、射电天文望远镜、卫星地面站,以及导弹和卫星的跟踪接收系统之中,有效地提高了接收机的灵敏度。人们在研制低噪声器件和低噪声接收系统的过程中,逐渐认识到用高温噪声源(如气体放电噪声源等)测量低噪声器件的性能,其精确度愈来愈满足不了要求,低噪声测 I. Introduction In recent years, the development of microwave low noise devices is very rapid. Low-noise mixers, transistor amplifiers and parametric amplifiers have been widely used in radar, radio telescopes, satellite ground stations, and missile and satellite tracking receiving systems to effectively improve receiver sensitivity. People in the process of developing low-noise devices and low-noise receiver system, and gradually realized that the use of high-temperature noise sources (such as gas discharge noise sources, etc.) to measure the performance of low-noise devices, the accuracy of their increasingly meet the requirements of low noise