Noise and Gain Measurements of Low Noise Amplifiers . Rausch- und Verstaerkungsmessung an Rauscharmen Vorverstaerkern

摘要

Suitable methods for the determination of noise and amplification properties of low noise preamplifiers are considered with regard to practically attainable measuring accuracy. The following error sources which disturb the determination of the input noise temperature are discussed separately: the uncertainty of the bath temperature of the noise standards, the precision of the feed line attenuation and the Y factor under consideration of three frequently used combinations of noise standards. It is shown that the noise measurement in combination with liquid helium is the most precise for large and small values of the input noise temperature. In addition, a method is described for determining the system noise temperature by two Y measurements with unknown antenna noise temperature, and simultaneous determination of the input noise temperature.