Cyrille Enderli

Experimental measurement of time difference of arrival

In this paper is described an experimental passive localization system based on SDR (Software Defined Radio) components. This system is designed to measure Time Differences of Arrival (TDOA) of radar pulses between two platforms. For a TDOA system, time error between the two receivers must be kept very low, which requires a very accurate way to synchronize the time bases. In this purpose, a custom offline synchronization method is proposed. The overall performances of the system are analyzed. In a small scale outdoor experiment, it has been shown to perform TDOA measurements accurately. The performances measured during this experiment are then extrapolated to a more realistic electronic warfare scenario.

Why synchronization is a key issue in modern Electronic Support Measures

The goal of this paper is to show that in order to achieve good localization performances with a modern Electronic Support Measure (ESM) system based on Time Difference Of Arrival (TDOA) and Frequency Difference Of Arrival (FDOA) measurements, it is necessary to have a precisely synchronized time base on every sensor. An application case is detailed to show how an imperfect synchronization causes degradations in the localization performances at the output of the system. It focuses on a simple scenario: two airborne receivers using TDOA and FDOA measurements to localize a stationary emitter. In the first section the synchronization process and its error model are defined. The second section presents simulations which show the influence of these errors on the estimation of TDOA and FDOA measurements. In the last section are discussed the final localization performances, based on the calculation of the Cramér-Rao Lower Bound (CRLB) using the previous corrupted estimates of TDOA and FDOA.

Design of a multi-resolution phase-coded waveform in the presence of a colored Gaussian clutter

In current airborne radars, detection and identification are done with two distinct waveforms. However, while the radar switches from one function to another, the target scene can change. In this paper, we propose a hybrid waveform combining intra and interpulse phase codes. This waveform is first processed in a low-resolution “channel”. Then, if a target is detected, the received signal is reprocessed in a high-resolution “channel”. Given the above scenario and assuming that the received data are disturbed by a colored Gaussian clutter, we address the optimization of the phase codes by searching the Pareto front of a multi-objective optimization problem. Finally, we aim at analyzing the sensitivity of the Pareto front to the clutter properties. For this purpose, we study whether a first-order autoregressive (AR) modelling for the clutter in the high-resolution case is relevant or not.

Experimental Analysis of Time Deviation on a Passive Localization System

In Electronic Warfare, and more specifically in the domain of passive localization, accurate time synchronization between platforms is decisive, especially on systems relying on TDOA (Time Difference Of Arrival) measurements. This paper investigates this issue by presenting an analysis in terms of synchronization performance of an experimental passive localization system based on off-the-shelf components. This system is detailed, as well as the methodology used to carry out the acquisition of real data. This experiment has been realized with two different kinds of clock. The results obtained in the two cases are compared through the analysis of their Allan time deviation. The choice of this metric is explained and its properties are discussed in the scope of an airborne bi-platform passive localization context. Conclusions are drawn regarding the overall performance of the system.

Influence of Synchronization Impairments on an Experimental TDOA/FDOA Localization System

In Electronic Warfare, and more specifically in the domain of passive localization, accurate time synchronization between platforms is decisive, especially on systems relying on TDOA (time difference of arrival) and FDOA (frequency difference of arrival). This paper investigates this issue by presenting an analysis in terms of final localization performance of an experimental passive localization system based on off-the-shelf components. This system is detailed, as well as the methodology used to carry out the acquisition of real data. This experiment has been realized with two different kinds of clock. The results are analyzed by calculating the Allan deviation and time deviation. The choice of these metrics is explained and their properties are discussed in the scope of an airborne bi-platform passive localization context. Conclusions are drawn regarding the overall localization performance of the system.

Analysis of a GLRT for the detection of an extended target

For a high-resolution radar, an extended target is characterized by a few main scatterers spread over several range gates not necessarily consecutive. The joint detections and localizations of these scatterers are of particular interest in order to estimate the range profile and identify the target. In this paper, we study a detector based on the Generalized Likelihood Ratio Test considering the unknown locations of the scatterers. Given the number of scatterers and using order statistics results, we derive approximations of the probability of false alarm and the probability of detection and localization which can be a relevant measure of performance in this context. Finally, a comparative study is carried out with other existing detectors.

Combining two phase codes to extend the radar unambiguous range and get a trade-off in terms of performance for any clutter

This paper deals with a phase-coded waveform which combines two binary phase codes, each impacting on specific properties of the radar receiving channel. After giving a detailed analysis of the expression of the received signal after processing when the Gaussian clutter is modeled by a pth-order autoregressive process, we focus our attention on the choice of the two phase codes: one aims at increasing the unambiguous range whereas the other is chosen by taking into account several criteria such as the detection performance. For this purpose, we suggest determining the Pareto fronts of 1st, 2nd and 3rd orders by means of an exhaustive search. Given the three Pareto fronts for different types of clutters simulated by making the AR parameters vary, we provide an automatic way to determine, before embedding it, the most robust phase codes using a fuzzy logic operator.

The eigencanceler as a uniform most powerful invariant test applied to spatial processing for jammer mitigation

The eigencanceler (EC) is a subspace detector that has been suggested in the last years as a robust and fast-converging alternative to GLRT-related methods for space-time adaptive radars. In this paper we consider the EC from an original invariance-based point of view for the problem of spatial anti jamming, where interference is not required to be normally distributed. We compare the performances of the EC and the standard adaptive matched filter for the problem considered, in term of signal to noise + interference ratio for both Gaussian and non-Gaussian interference.