Qinzhen Hu

Radio Frequency Interference Cancelation for Skywave Over-the-Horizon Radar

In the user-congested high-frequency band, skywave over-the-horizon radar (OTHR) is easily interfered by radio frequency interference (RFI). Among the existing methods, transient and nontransient RFIs are suppressed by time-domain methods and beamforming methods, respectively. However, the existing beamforming methods cannot work in transient cases, whereas the time-domain methods are usually time-consuming and suffer performance loss in mass interference cases. Therefore, a unified method for two kinds of RFI cancelation is preferred. In this letter, based on the frequency characteristics of the RFI and the regular processing procedure of the skywave OTHR, an adaptive RFI cancelation scheme is proposed. In this scheme, the RFI is localized in the frequency domain, after which snapshots are chosen to complete the frequency-domain adaptive beamforming. The proposed scheme makes it possible to completely cancel both kinds of RFI in the beamforming stage, which is timesaving and proper for practical application. The performance of the proposed scheme is evaluated by experimental data.

Target detection in distributed MIMO radar with registration errors

In this paper, we consider a target detection problem in a distributed multiple-input multiple-output radar with registration errors. Registration errors mean the alignment errors when observation data from different distributed radars are transformed in a common coordinate system. Our study is motivated by the fact that the perfect registration condition is unavailable in practice, even after a registration process. A model for the imperfect registration is introduced where an uncertainty window centered on the cell being tested along range and azimuth in each spatial diversity channel is employed. A generalized likelihood ratio test (GLRT) detector and a Bayesian likelihood ratio test detector are developed based on the uncertainty windows. The probability of false alarm of the proposed GLRT detector is derived. For convenience of comparison, we also analyze the detection performance of the conventional likelihood ratio test (LRT) detector with registration errors. Simulation results demonstrate that the detection performance of the two proposed detectors outperform the conventional LRT detector in the imperfect registration case.

Spectrum reconstruction in the sky-wave OTHR using GAPES

The performance of a sky-wave over-the-horizon radar (OTHR) is severely degraded by the transient interference such as lighting and radio-frequency interference (RFI). After interference excision, the target detection performance is mainly determined by the performance of Doppler spectrum reconstruction. In this paper, instead of the regular linear prediction interpolation method, the gapped-data amplitude and phase estimation (GAPES) method is used for the Doppler spectrum reconstruction. The experimental results show that it is an effective way to achieve spectrum reconstruction.

Computationally Efficient Transient Interference Excision Method for Skywave Over-the-Horizon Radar

The skywave over-the-horizon radar (OTHR) has attracted considerable attention for its ability of out-of-sight surveillance. However, in practice, its operational performance is severely degraded by transient interferences. Some previous works focus on time-domain methods to achieve transient interference suppression and cannot get rid of the corruption segment blanking and data interpolation. In fact, the data interpolation method is usually time-consuming and may suffer performance loss. To avoid data interpolation, some interpolation-free methods are proposed and show superior performance. However, the significant computational costs impede the application in reality. In this letter, a new method for transient interference suppression is proposed. After interference localization, a signal subspace, representing the clutter and target, is constructed by the interference-free data. Then, transient interferences are excised by solving a bicriterion optimization problem that minimizes the quadratic fitting error and the energy orthogonal to the signal subspace simultaneously. The proposed method can excise transient interferences with clutter and potential target echoes preserved at the same time; thus, data interpolation is no longer needed. The proposed method is evaluated by experimental data collected from a trial skywave OTHR, and the results verify its effectiveness.

Spatial resolution cell based centralized target detection in multistatic radar

Abstract The problem of spatial resolution cell (SRC) based centralized target detection in multistatic radar is considered. Due to the fact that using the observation data from different radar sites can result in a much smaller uncertainty volume, the SRC of multistatic radar is usually an intersection of the overlapping range, azimuth and elevation resolution cells of all spatial diversity channels (SDCs). Then, the target detection problem in multistatic radar can be considered as deciding whether a target is present in each probed SRC. In this paper, a general scheme of the SRC based centralized target detection in multistatic radar is proposed. Considering that different neighboring SRCs of multistatic radar may correspond to the same range, azimuth and elevation resolution cell of one SDC, the desired signals or noises from these neighboring SRCs hence can be mutually dependent. Motivated by this, the symbiosis relationship of these neighboring SRCs in exceeding the test threshold during the process of centralized target detection is specifically studied. Furthermore, the performance of the peak search method to decide which SRC on earth contains the target of interest is accordingly analyzed.