Residual AM and PM Noise of Selected X-Band Amplifiers
Abstract
In microwave systems design, amplitude modulation (AM) noise is often ignored relative to phase modulation (PM) noise. However, in high-performance applications requiring ultra-low PM noise, AM noise becomes a critical limiting factor due to AM-to-PM conversion mechanisms. Because AM noise specifications are rarely, if ever, provided for commercial microwave components, this study characterizes the residual AM and PM noise of several 10 GHz amplifiers. We present performance data for various Heterojunction Bipolar Transistor (HBT) amplifier designs and demonstrate the noise reduction achieved through power-summed configurations. For example, a discrete-die GaAs HBT amplifier achieves residual PM noise below −160 dBrad2/Hz and AM noise of approximately −155 dB/Hz at a 1 kHz offset in a quad power-summed configuration. A notable finding is that the majority of amplifier designs surveyed in this study exhibit higher AM noise relative to their PM noise, with only a few exceptions. The impact of bias supply quality on residual noise is also quantified, demonstrating that the choice of voltage regulator is a first-order design parameter below 1 kHz offset.
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BibTeX
@misc{hati2026residual,
title = {{Residual AM and PM Noise of Selected X-Band Amplifiers}},
author = {Archita Hati and Craig Nelson and Scott Littrell},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.03178},
eprint = {2610.03178},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.03178},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Residual AM and PM Noise of Selected X-Band Amplifiers
AU - Archita Hati
AU - Craig Nelson
AU - Scott Littrell
PY - 2026
DA - 2026/10/02
PB - arXiv
DO - 10.48550/arxiv.2610.03178
UR - https://arxiv.org/abs/2610.03178
AB - In microwave systems design, amplitude modulation (AM) noise is often ignored relative to phase modulation (PM) noise. However, in high-performance applications requiring ultra-low PM noise, AM noise becomes a critical limiting factor due to AM-to-PM conversion mechanisms. Because AM noise specifications are rarely, if ever, provided for commercial microwave components, this study characterizes the residual AM and PM noise of several 10 GHz amplifiers. We present performance data for various Heterojunction Bipolar Transistor (HBT) amplifier designs and demonstrate the noise reduction achieved through power-summed configurations. For example, a discrete-die GaAs HBT amplifier achieves residual PM noise below −160 dBrad^2/Hz and AM noise of approximately −155 dB/Hz at a 1 kHz offset in a quad power-summed configuration. A notable finding is that the majority of amplifier designs surveyed in this study exhibit higher AM noise relative to their PM noise, with only a few exceptions. The impact of bias supply quality on residual noise is also quantified, demonstrating that the choice of voltage regulator is a first-order design parameter below 1 kHz offset.
ER -