Experimental Study of AM and PM Noise in Cascaded Amplifiers

Inari Badillo,Joaquín Portilla

doi:10.3390/electronics11030470

Abstract

An experimental study of amplitude modulation (AM) and phase modulation (PM) 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 (NF) 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.

Highlights

Amplitude modulation (AM) and phase modulation (PM) noises have always been important concerns in radio communication, radar, radiometry, or RF and microwave particle acceleration, among other applications
Signal cascaded white showed noise adde amplifiers are drivenIn into compression,amplifiers, the effective NFthe experiments that effective noise figure (NF) rise with carrier input power, and this becomes faster when adding quently amplified by the stages afterwards, which in turn adds its amplification stages due to boosted non-linear effects in the amplifying chain, producing an of the amplifier increases slightly with the augmentation the white noiseoverall contributions with respect to the small-signal regime
An experimental study of the AM and PM noise in cascaded amplifiers working in small- and large-signal regimes was reported, including the evaluation of the AM

Summary

Introduction

Amplitude modulation (AM) and phase modulation (PM) noises have always been important concerns in radio communication, radar, radiometry, or RF and microwave particle acceleration, among other applications (see, for instance, [1,2,3,4,5,6,7,8,9,10]). Measurement and simulation results have shown that AM and PM noise contributions are identical just in the white region of the noise spectra and only in the case of the amplifier working under linear conditions [12,13]. The study was extended 2toof the evalu the AM–PM noise cross-correlation by measurement of the coherence function fined in terms of noise power spectral densities, as a function of the offset from th either for a given input or output carrier power level. This is more noticeable as the frequency, from low-frequency noise to white contributions to the carri amplifiers are driven into compression. Measurement the carrier noise in RFSetup and microwave cascade amplifiers are considered

Measurement

Discussion

Conclusions