Experimental Study of AM and PM Noise in Cascaded Amplifiers

TL;DR

This paper presents an experimental analysis of AM and PM noise in cascaded amplifiers, examining how noise spectra, correlation, and noise figure vary with stages and input power, revealing low correlation levels and noise figure reduction with more stages.

Contribution

It provides new experimental data on AM and PM noise behavior, correlation, and noise figure in cascaded amplifiers across different configurations and power levels.

Findings

AM and PM noise spectra depend on number of stages and input power.

Correlation between AM and PM noise is generally low, with some peaks at specific conditions.

Effective noise figure decreases as the number of amplification stages increases.

Abstract

An experimental study of amplitude modulation and phase modulation noise spectra in cascaded amplifiers was carried out as a function of the number of amplification stages and the input power. Flicker and white noise contributions were determined, as well as effective noise figure from AM and PM noise spectra from small signal to large signal regimes. Simultaneous measurements of AM and PM noise were performed, and associated correlation was measured as a function of the offset frequency from the carrier. Measurements exhibited, in general, quite low AM PM correlation levels both in the flicker and white noise parts of the spectrum. In some particular amplifier configurations, however, measurements showed some peaks in the correlation at some specific input power levels in the transition zone, from a quasi-linear to strong compression. The results show that the effective noise figure decreases with the number of stages for a given carrier output power level.