Noise Figure vs. PM Noise Measurements: A Study at Microwave Frequencies,

Published

January 1, 2003

Author(s)

Archita Hati, David A. Howe, F L. Walls, D. Walker

Abstract

This paper addresses two issues: (i) it compares the usefulness of phase-modulation (PM) noise measurements vs. noise figure (NF) measurements in characterizing the merit of an amplifier, and (ii) it reconciles a general misunderstanding in using -174 dBc/Hz (relative to carrier input power of 0 dBm) as thermal noise level. The residual broadband (white PM) noise is used as the basis for estimating the noise figure (NF) of an amplifier. We have observed experimentally that many amplifiers show an increase in the broadband noise of 1 to 5 dB as the signal level through the amplifier increases. This effect is linked to input power through the amplifier's nonlinear intermodulation distortion. Consequently, this effect is reduced as linearity is increased. It is important to note that NF is sometimes used as a selection criteria for an amplifier but yields no information about potentially important close-to- carrier 1/f noise of an amplifier, whereas PM and amplitude modulation (AM) noise measurements do. We have verified theoretically and experimentally that the single-sideband PM (and AM) noise floor due to thermal noise is -177 dBc/Hz, relative to a carrier input power of 0 dBm.

Proceedings Title

2003 Joint Mtg. IEEE Intl. Freq. Cont. Symp. and EFTF Conf.

Conference Dates

May 4-8, 2003

Conference Location

Tampa, FL

Conference Title

Proc. 2003 Joint Mtg. IEEE Intl. Freq. Cont. Symp. and EFTF Conf.

Pub Type

Conferences

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Citation

Hati, A. , Howe, D. , Walls, F. and Walker, D. (2003), Noise Figure vs. PM Noise Measurements: A Study at Microwave Frequencies,, 2003 Joint Mtg. IEEE Intl. Freq. Cont. Symp. and EFTF Conf. , Tampa, FL, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=105255 (Accessed October 10, 2025)