Improved Y factor noise measurement using the second stage contribution to advantage

The ultimate limitation to characterizing noise in microwave amplifiers derives from the noise inserted by the front-end of the measurement set. Typically a high-gain low noise preamplifier is used in the measurement set to improve accuracy. Even then there is a limit to the minimum noise factor that can be measured. In this paper an extended Y-factor noise measurement technique is presented that utilizes an amplifier stage identical and in addition to the amplifier under test to enhance measurement accuracy. Utilizing a calibrated noise source, the output noise power of first a forward cascade of the two amplifiers is measured and then that when the amplifiers are arranged in reverse cascade. The use of a spectrum analyzer or power meter with a readily measured change in noise power reading is required as well as a calibrated noise source.