Wideband RFI Cancellation for High-sensitivity Phased Array Receivers
with True Time Delays and Truncated Hadamard Projection
Abstract
Radio frequency interference (RFI) is a significant challenge for
high-sensitivity phased array instruments. RFI can be suppressed using
digital signal processing, but to improve dynamic range for wideband
RFI, it can be desirable to remove interference in the analog domain
before sampling. In previous work, it has been shown that analog true
time delay (TTD) stages with a truncated Hadamard transform can place a
wide-band spatial null on RFI from a given direction of arrival. We show
that TTD and Hadamard projection is mathematically equivalent to the
classical, narrow-band subspace projection beamformer, but with a
structure that allows efficient implementation in analog circuitry.
Simulation results show that TTD and Hadamard projection can place deep
nulls on wideband RFI signals and still achieve SNR performance
comparable to the optimal digital maximum signal to interference and
noise ratio beamformer.