Out-of-Band Radiation from Antenna Arrays Clarified

TL;DR

This paper clarifies that non-linearities in RF transceivers cause correlated out-of-band emissions in antenna arrays, which can be beamformed into the same direction as the main signal, challenging previous claims.

Contribution

It demonstrates that out-of-band radiation from antenna arrays is correlated and beamformed, providing a corrected understanding contrary to recent literature.

Findings

Out-of-band emissions are correlated across antennas.

Non-linearities cause beamformed out-of-band radiation.

This radiation can align with the main signal direction.

Abstract

Non-linearities in radio-frequency (RF) transceiver hardware, particularly in power amplifiers, cause distortion in-band and out-of-band. Contrary to claims made in recent literature, in a multiple-antenna system this distortion is correlated across the antennas in the array. A significant implication of this fact is that out-of-band emissions caused by non-linearities are beamformed, in some cases into the same direction as the useful signal.