Non-stationary interference cancellation in HF surface wave radar

Abstract

Abstract-High frequency (HF) interference in surface wave over-the-horizon (OTH) radars typically exhibits a time-varying or non-stationary spatial structure. Adaptive beamformers that update the spatial filtering weight vector within the coherent processing interval (CPI) are likely to suppress such interference most effectively, but the intra-CPI antenna pattern fluctuations result in temporal de-correlation of the clutter which severely degrades sub-clutter visibility after Doppler processing. A robust adaptive beamformer that effectively suppresses non-stationary interference without degrading sub-clutter visibility is proposed. The new algorithm is computationally efficient and suitable for practical implementation. Its operational performance is evaluated using experimental data recorded by the Iluka HF surface wave (HFSW) OTH radar, located near Darwin in far north Australia.

Subspace Impulsive Interference Suppression in Othr

“…where S is the power of pseudo-target or IMI, N is the power of other components in (7). When the SN R is high enough, this correlation matrix R xx may have two separated parts of eigenvalues.…”

“…The ground clutter normally exhibits as a narrow-band signal with Doppler frequency close to zero. The ocean clutter, on the other hand, is usually modeled as two Bragg peaks (first-order scattering) and surrounding continuum (high-order scattering), where the Bragg peaks usually dominate the ocean clutter since their amplitudes are generally two orders of magnitude higher than those of the surrounding continuum [7,8]. Secondly, the IMI brings broadband noise with high-amplitude into the entire range of Doppler search space, significantly limiting the target detection performance of the OTHR.…”

“…There are three categories of detection and suppression methods in existing literatures, including spatial adaptive processing (SAP) [7,8,16,23], space-time adaptive processing (STAP) [17,18,26,29] and temporal [12, 19-21, 24, 27]. Although the STAP or SAP algorithms may reject spatial structured interference such as radio frequency interference (RFI) [8], but there still exists a potential that leaking energy of IMI from sidelobe will exhibit as temporal IMI.…”

Wideband signal design for over-the-horizon radar in cochannel interference

“…Fabrizio proposes adaptive beamforming techniques in spatial domain [9,10]. Suppressing interference in time domain and frequency domain fundamentally http://asp.eurasipjournals.com/content/2014/1/159 involves estimating parameters of interference and then suppressing, with iterative algorithm widely employed, like least-mean-square filters [11,12] and orthogonal subspace projection filtering [13].…”

“…In Guo's schemes, there is one requirement that interference training should be performed with ocean/ground clutter and strong targetlike components excluded, which is a hard task in skywave OTH radar. Besides, for interference cancelation performed on received data, there is one potential risk that employing nonlinear algorithm too much in signal process may cause unexpected influences, e.g., degrading clutter visibility [9]. Also, algorithms designed for suppressing narrowband interference are unsuitable for broadband interference or colored noise with diffused energy.…”