Doppler considerations and phase manifold effects for anti-jam electronics

Due to the widespread use of anti-jam electronics (AJ-E) with controllable radiation pattern antennas (CRPA) in estimating direction of arrival (DOA), considerations of Doppler and contributions through antenna phase manifold should be considered for both error characterization in AJ-E covariance output and effectiveness of nulling algorithms. By considering the manifold effects, an observability space can be estimated a priori and provided to down-stream DOA filters. The observability space also provides an expected error characterization for AJ-E's signal covariance matrix used to derive weights for their individual antenna element feeds and taps. This estimated covariance matrix is typically derived from a windowed set of In-phase and Quadrature phase (IQ) samples collected over a set length of time (typically 1 ms). Most per-element delays are constant over this time period, but some vehicles hosting the AJ-E have roll rates which, when mapped through the antenna phase manifold, can create Doppler coloring of the covariance estimate. Even with benign roll rates, the manifold coloring of the Doppler can be significant. This paper examines the Doppler influence through a commercial CRPA's phase manifold and maps the per-component phase error perceived. The paper demonstrates the effect through software simulated IQ data samples and a commercial phase manifold.