Jean-Michel Quellec

Analysis of K-distributed sea clutter and thermal noise in high range and Doppler resolution radar data

This paper deals with the distribution of signal received by airborne radar in Doppler domain for maritime surveillance mission. It is composed of thermal noise and sea clutter which its intensity may be described by a compound K-distribution. The data used was recorded in high range and Doppler resolution by monostatic coherent X-band radar above Mediterranean sea and Atlantic ocean. The statistics of the sea clutter plus noise distributions have been estimated by calculating the complementary cumulative density function of real data. The variation of the fitted shape parameter is compared and discussed in a wide range of data under various conditions.

Accuracy studies for TDOA-AOA localization of emitters with a single sensor

This paper investigates the problem of source localization using a single sensor and multipath signals in a electromagnetic warfare (EW) context. Time difference of arrival (TDOA) and angle of arrival (AOA) measurements are used to localize transmitters. This approach is interesting in the sense that no a priori knowledge of scatterers is required. For this localization approach, the minimal number of components (emitters and reflectors) is determined. Attainable accuracies of our method for the different possible configurations are discussed using the Cramér-Rao lower bounds.

Polarisation influence on sea clutter properties and radar detection performance in X-band for low grazing angles

This paper establishes a comparison of sea clutter properties and radar detection performance depending on polarisation and conditions of observation. A theoretical approach based on the most common models for sea clutter properties first shows that the polarisation yielding the best performance depends on a precise set of parameters, namely the grazing angle, wind speed and radar height. The models used here concern the reflectivity coefficient, the amplitude statistics, and the spectral behaviour. A detailed statistical analysis of a sea clutter database then confirms the effects of polarisation on the sea clutter properties, and the influence of this set of parameters on the best polarisation in terms of detection performance. The vertical polarisation thus proves to yield much better detection performance for low grazing angles and high sea states, for both coherent and non-coherent detection schemes. The conditions for which both vertical and horizontal polarisations yield the same level of detection performance are also analysed.

Localization of radar emitters from a single sensor using multipath and TDOA-AOA measurements in a naval context

This paper investigates the problem of source location from a single sensor using direct and indirect signals in a maritime context. To localize the emitters, we propose to exploit time difference of arrival (TDOA) and angle of arrival (AOA) measurements. The proposed approach uses any a priori knowledge of the reflectors positions. However, in practice, it is necessary to solve an assignment problem. It consists in associating each pair of TDOA-AOA measurement to a given reflector, this pair being already associated to a given emitter. In order to show the potential of our approach, numerical results using simulated and real data are proposed.

Sea-spike analysis in high range and Doppler resolution radar data

This paper deals with the analysis of coherent spiky sea clutter data recorded by a high range and Doppler resolution airborne radar for maritime surveillance mission at low grazing angle. A general description of sea-spikes is given: physical explanations, statistical modelling and identification with three different methods. The following properties are then analysed for our data: 1/ temporal characteristics such as radar cross section, range spread, life time and pulse to pulse correlation with frequency agility, 2/ spectral characteristics such as mean frequency and Doppler spread.

GLRT Detection for Range and Doppler Distributed Targets in non-Gaussian Clutter

A Generalized likelihood ratio test (GLRT) is derived for adaptive detection of range and Doppler distributed targets. The clutter is modelled as a Spherically Invariant Random Process (SIRP) and its texture component is range dependent (heterogeneous clutter). We suppose here that the speckle component covariance matrix is known or estimated thanks to a secondary data set. Thus, unknown parameters to be estimated are local texture values, the complex amplitudes and frequencies of all scattering centers. The proposed detector assumes a priori knowledge on the spatial distribution of the target and has the precious property of Constant False Alarm Rate (CFAR) with the assumption of a known speckle covariance matrix or by the use of frequency agility.

GLRT detection for range and Doppler distributed targets in non-Gaussian clutter

A Generalized likelihood ratio test (GLRT) is derived for adaptive detection of range and Doppler distributed targets. The clutter is modelled as a Spherically Invariant Random Process (SIRP) and its texture component is range dependent (heterogeneous clutter). We suppose here that the speckle component covariance matrix is known or estimated thanks to a secondary data set. Thus, unknown parameters to be estimated are local texture values, the complex amplitudes and frequencies of all scattering centers. The proposed detector assumes a priori knowledge on the spatial distribution of the target and has the precious property of Constant False Alarm Rate (CFAR) with the assumption of a known speckle covariance matrix or by the use of frequency agility.