Hardware Limitations of Receiver Channel-Pair Cancellation Ratio

Abstract

Interference cancellation techniques in multi-channel radar and communication systems, such as adaptive beamforming, are only effective if the response of each channel used is well matched. Though hardware variations between channels limit the intrinsic channel response match, digital equalization techniques improve channel-to-channel matching, as measured by the channel-pair cancellation ratio (CPCR). Digital receiver channel nonlinearities such as analog-to-digital converter (ADC) saturation and third-order nonlinearities, however, limit the level of channel matching achievable. We compare the effect of the use of linear frequency modulation (LFM) and band-limited Gaussian noise measurement (BLGN) signals on CPCR. We determine the impact of ADC saturation and analog-component third-order nonlinearities on each measurement signal through analysis, simulation, and experiments using a pair of S-band digital receivers. We show that the maximum achievable CPCR is lower for BLGN than LFM measurement signals due to ADC saturation and third-order nonlinearities.