Passive Radar DPCA Schemes With Adaptive Channel Calibration

Abstract

This paper addresses the problem of direct signal interference (DSI) and clutter cancellation for passive radar systems on moving platforms employing displaced phase centre antenna (DPCA) approach. Attention is focused on the development of signal processing strategies able to compensate for the limitations deriving from amplitude and phase imbalances that affect the two channels employed on receive. First, we show that using the signal received from the illuminator of opportunity as a source for channels calibration might be ineffective when DSI and clutter echoes have different directions of arrival, due to the effect of angle-dependent channel imbalance. Then, a two-stage strategy is proposed, consisting of a preliminary DSI removal stage at each receive channel, followed by a clutter-based calibration approach that basically enables an effective DPCA clutter suppression. Different strategies for channel calibration are proposed, aimed at compensating for potential angle and range dependent channel errors, based on the maximization of the cancellation performance. Effectiveness of this scheme is shown against experimental data from a DVB-T based moving passive radar, in the presence of both real and synthetic moving targets.

Facing channel calibration issues affecting passive radar DPCA and STAP for GMTI

“…However, as mentioned, significant limitations to the DPCA performance may come from the presence of interchannel imbalance, which is in general function of the angle of arrival. Adaptive digital channel calibration techniques, like those analysed in [10], are then required to mitigate this problem by compensating for the angle-dependent channel errors. These limitations of the DPCA approach and the need for a localized adaptation capability, lead towards the adoption of a more sophisticated but more flexible adaptive space-time processing (STAP) solution.…”

“…In order to compensate for the imbalance effect and improve the cancellation performance, a digital channel calibration can be applied, directly operating on the range-Doppler maps, before DPCA subtraction. Specifically, we consider the Doppler dependent calibration (DDC) approach presented in [10], which exploits the duality between angle of arrival and Doppler frequency of stationary scatterers. A set of complex correction coefficients is estimated and separately applied at each Doppler bin within the endo-clutter region, so as to minimize the output clutter power.…”

“…First attempts of providing passive radar with GMTI capability exploited the displaced phase centre antenna (DPCA) approach [4]- [10]. DPCA performs a non-adaptive subtraction of radar echoes collected by two along-track displaced receiving channels at the time that their two-way phase centres occupy the same spatial position [3].…”

“…Strategies for adaptive digital channel calibration based on the received data are proposed in [11]- [12] for the case of SAR-GMTI. In [10], effective solutions are developed to face the critical aspects of the passive radar case. Such solutions prove to be largely required to preserve clutter suppression capability against the imbalance observed in experimental data.…”

The Impact of Channel Errors in Passive Coherent Location Radar using FM Base Stations

“…The influence of channel calibration issue is analysed for DVB-T based multi-channel PCL system in ground moving target indication (GMTI) [23]. The problem of direct signal interference and clutter cancellation are discussed in [24] for passive radar systems. Different channel calibration strategies are proposed to improve the clutter cancellation performance.…”