Effects of third-order nonlinearities on jamming cancellation

Hardware errors adversely affect the performance of jamming sidelobe cancellation in a digital beamforming array that combines array elements into subarrays for digital combining and uses auxiliary channels to obtain an estimate of the jammer signals. Analysis is needed to determine how much hardware error can be tolerated to obtain a desired level of jamming cancellation performance. Under a specific set of assumptions, we derive analytical, closed-form expressions that relate third-order nonlinearities (TONs) to jamming cancellation power residue in a sidelobe cancellation system. We show that the TON residue is dominated by the subarray pattern. We demonstrate that for one jammer and many auxiliaries, if the auxiliary channels have similar nonlinear parameters to the subarrays, the sidelobe canceller can remove the TON components in the sum channel to obtain almost ideal (i.e., no nonlinearities in either subarray or auxiliary channels) performance.