https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018RS006682

A Robust Feature Extraction and Parameterized Fitting Algorithm for Bottom-Side Oblique and Vertical Incidence Ionograms

In skywave over-the-horizon radar, the ionosphere often supports multiple propagation paths, and a single target can appear as a family of returns. This paper presents two new tracking approaches for this environment: The first uses measurement fusion, and the second uses group-target track-before-detect algorithm. In contrast to previous studies, we find that the biggest benefit is not improved detection sensitivity but rather associating the whole pattern of multipath returns significantly improves the ability to follow maneuvers.

Detection and Tracking of Multipath Targets in Over-the-Horizon Radar

In this paper, we analyze the levels of performance of the (full or reduced versions of) space-time adaptive processing (STAP) algorithms applied to high-frequency surface wave radars (HFSWRs) for marine target detection to verify whether this family outperforms the usual moving target indication (MTI) algorithms. In fact, STAP algorithms have well-known drawbacks (e.g., large amount of secondary data). The propagation and backscattering of radar signals are included in the covariance matrix calculation. Since the propagation and backscattering have to be derived from physical features of the sea (e.g., sea Doppler) and the atmosphere, we also include the difference induced by the waveform (pulsed radar/chirp) in our study. Moreover, since the inverse covariance matrix is used in the target detection algorithms, matrix conditioning is also inspected for practical implementation reasons. We numerically detail the performance (signal noise clutter ratio and conditioning number of the STAP algorithms) with regards to the MTI performance for several configurations of radar and sea state. These results show that the improvements of signal noise clutter ratio are counterbalanced by a raise of the conditioning number, except in the case of eigencanceler approach. The sea-state parameters have few effects on the performance unlike to radar parameters.

Theoretical Performance of Space-Time Adaptive Processing for Ship Detection by High-Frequency Surface Wave Radars

In this paper, we consider the Doppler signatures of local multipath target signals in an over-the-horizon radar and the objective is to separate signals corresponding to the ordinary (O) and extraordinary (X) propagation modes. As signals of these two modes are reflected at different ionosphere heights, the rendered Doppler signatures are more complicated and cannot be directly analyzed for parameter estimation using conventional local multipath models which are developed for a single propagation mode. We consider a mixed O/X-mode signal model and analyze the resulting Doppler signatures comprising of more signal components. It is shown that sparsity-based methods estimate the Doppler components with improved resolution and accuracy. Moreover, the proposed group sparsity-based strategy enables separation of the resolved Doppler components corresponding to the two propagation modes. We present the simulation results for a challenging scenario where the multipath Doppler signatures corresponding to the two modes are interlaced.

Doppler Signature Separation of Mixed O/X-Mode Over-The-Horizon Radar Signals

An Australian network of oblique angle-of-arrival (AoA) ionosondes was installed as part of the ELOISE experimental campaign in September 2015, aimed at an improved understanding of the spatial and temporal structure of traveling ionospheric disturbances (TIDs) at mid-latitudes. In this paper, the array design and signal processing for the AoA sounder is described, along with a sample of results showing typical disturbance signatures. Realistic parameterized models of electron density perturbations, along with geometric ray tracing, were used to synthesize the effects of medium to large scale TIDs on the sounder observables and aid in classifying the measurements.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018RS006613

Observations and Modeling of Traveling Ionospheric Disturbance Signatures From an Australian Network of Oblique Angle-of-Arrival Sounders

Presents a collection of slides covering the following topics: high frequency over-the-horizon radar; HF channel model; time-varying adaptive beamforming; space-time adaptive processing; GLRT detection schemes; HF passive radar; blind signal separation; multipath-driven geolocation and MIMO OTHR concept.

High Frequency Over-the-Horizon Radar

We consider a multiple-input multiple-output (MIMO) dual function radar communication (DFRC) system employing frequency hopping (FH) radar waveforms. The DFRC system embeds communication symbols using code-shift keying (CSK) strategy. Each symbol is represented by a phase modulated pulse code sequence which multiplies the radar hops in fast-time before transmitted from the MIMO radar platform. This strategy allows for reduced clutter modulation caused by changed radar waveforms within coherent processing interval (CPI). We analyze the effect of this communication symbol embedding scheme on range sildelobe levels (RSLs) and derive the DFRC probability of target detection. We show that the DFRC waveforms enhances target visibility leading to improved target detection compared with the FH radar without signal embedding.

Giuseppe A. Fabrizio

Papers

High Frequency Over-the-Horizon Radar

Target Detection in Frequency Hopping MIMO Dual-Function Radar-Communication Systems