Analysis and Mitigation of Receiver Induced Nonlinearities on Pulse-Doppler Radars

Receiver nonlinearities can degrade pulse-Doppler radar performance when strong interferers are present. Non-linear equalization (NLEQ), typically used to digitally mitigate receiver distortions, has the potential to reduce intermodulation distortion (IMD) and cross-modulation distortion (CMD) that may be incurred when strong adjacent channel signals are present. This article reports on an investigation of NLEQ's viability to counter these deleterious effects and improve radar system performance. A simulation was developed analyzing the received signal for a weak target return in the presence of a strong adjacent band interferer, which was present for a fraction of the coherent processing interval (CPI). The receive signal's spectral regrowth increased the radar's in-band noise floor and corrupted the magnitude and phase of the target response, degrading the receive pulse-Doppler processing. It is shown that NLEQ can be used to compensate for these receiver-induced nonlinearities thus improving radar system performance.