Optimum-setting and calibration procedures for heterodyne measurements of amplitude and phase noise in high-frequency amplifiers

Abstract

An overview of several calibration stages has been studied and developed to obtain an optimum setting for phase and amplitude noise measurements through heterodyne techniques, which allows to measure white and flicker noise from amplifiers in the presence of a carrier signal. A technique to obtain a reliable calibration of phase and gain conversion of the measuring blocks is also presented, where the calibration of conversion factors and null conditions, using amplitude and phase modulators for each, phase and amplitude noise levels, have been fully characterized to suppress uncertainties in the measuring process. Furthermore, we introduce a procedure to measure noise of amplifiers in the presence of carrier signal based on a reference noise source and a known lossy line, which allows to determine the noise delivered from the source generator, and the contribution of the setup required for the measurement. We have found a good correlation of the measurements in small signal in comparison with the Y-factor. White noise of matched passive components was measured with the technique presented, obtaining an error of ±0.15 dB. Measurements of an SiGe-HBT amplifier designed for low phase noise are also reported. The technique has also been applied for flicker noise measurements.