A new blind adaptive antenna array for GNSS interference cancellation

This paper introduces a new blind adaptive antenna array as a possible solution to the interference cancellation problem. This new technique is compared to three classical ones over two different sensor radiation patterns. Special attention is paid to the array compatibility with a conventional GNSS receiver. A wide radiation pattern sensor is shown to improve the positioning accuracy by maximizing the satellite constellation visibility. Finally, the new processor demonstrates its superiority in term of positioning accuracy in presence of strong interferences. However, its phase response may make it incompatible with classical GNSS receivers. Some efforts must be done to stabilize it

Effects of rotor blade modulation on GNSS anti-jamming algorithms

In hostile environment, Global Navigation Satellite System (GNSS) could be disturbed by intentional jamming. Many adaptive algorithms have been developed to deal with these threats, among which use of antenna arrays is one of the most efficient. However, most of them have been designed under stationary hypothesis and their performances in harsher environments are questionable. For instance, when a GNSS receiver is placed near rotating bodies, the signal undergo complex and non-stationary effects called Rotor Blade Modulation (RBM). These variations can degrade significantly anti-jamming performance. This paper investigates the impact of the RBM on three conventional space-time adaptive processing (STAP). First, to simulate the RBM, the signal received by an antenna mounted on a helicopter is computed thanks to electromagnetic (EM) asymptotic methods. Then, to quantify precisely the loss in performance of each algorithm, we compare post correlation carrier to noise ratio (post - C/N0) and covariance matrix estimation with respect of the time. Finally, the simulation results are confirmed by experiments conducted on an EC-120 helicopter with an L-band Continuous Wave (CW) jammer

Performances of conformal and planar arrays

Static and dynamic deformations can have a severe impact on the performance of conformal antennas on aircrafts and other vehicles. Therefore it is essential to study the different deformation and vibration mechanisms and their influence on the antenna's radiation pattern. This presentation gives an overview of different approaches concerning electromagnetic modelling of array antennas and investigations on antenna deformations presented in the scope of TG20

NEPTUNE : Radar naval faible puissance de veille et désignation

International audienceLa présente communication décrit les travaux effectués dans le cadre du projet NEPTUNE, visant au développement d'un radar naval de faible puissance de veille et de désignation. Dans ce cadre, la détection de petite cible en incidence très rasante est recherchée, pour des états de mer variés. Pour cela, la base de données CSIR a été particulièrement étudiée et l'analyse qui en a été faite a permis de mettre en lumière certaines caractéristiques du fouillis et du couplage cible-mer. Son exploitation a apporté des éléments utiles au développement d'un modèle de génération de fouillis de mer par l'équipe propagation de l'ONERA/DEMR, mais a permis également l'analyse de performances de détecteurs développés par l'équipe de traitement du signal. L'objet de cette communication est de présenter des résultats représentatifs des phénomènes physiques en jeu, ainsi que des résultats en détection de cibles

Optimal STAP algorithms to GNSS receivers

The use of SpaceTime Adaptive Processing (STAP) algorithms to mitigate the detrimental effects of jamming upon Global Navigation by Satellite Systems (GNSS) receivers has gained significant interest in the signal processing community. In this paper, we consider STAP as an enhancement to conventional spaceonly Controlled Radiation Pattern Antennas (CRPA) for GNSS applications. We found that accurately characterizing the antijamming performances requires to model together the STAP filter and the receiver correlator. We first show that the array output Signal to Noise plus Interference Ratio (SINR) is not an appropriate criterion to characterize STAP performances in the GNSS context, one have to consider the STAPpluscorrelator output SINR. Then, by analyzing the post correlation noise power, we derive a close form expression of the STAPpluscorrelator SINR, which allowed us to derive the optimal temporal constraint and a simplified version. These constraints may be used with space constraints either to steer beams or form nulls. Their robustness to linear technological defects is also studied. We point out that the processors based on this criterion allow restoring the defects and interference free performances within a 5 dB margin. Finally, the simplified processor is the preferred one: it exhibits good interference cancellation capacities in presence of technological defects, and requires neither any hybridization with the receiver nor prior knowledge of the received modulation; moreover it can be used both with BPSK and BOC modulation waveforms

Stabilizing the phase response of blind array processors for GNSS interference cancellation

This paper considers blind adaptive antenna arrays as a possible solution to the interference cancellation problem in the GNSS context. The weight vector update in blind nullformers can introduce phase jumps not suitable for a generic GNSS receiver. In order to force a null imaginary part of the array’s response, we consider the design of two classes of blind symmetric arrays with conjugate symmetric weights. Finally, one of both provides a null phase response of the processor; the price is half the degrees of freedom of the array that cannot be used to cancel interferences

Multi path and jam resistant antennas for GNSS receivers

In GNSS applications, multipath errors and jamming threats are still one of the major error sources or service unavailability in conventional receivers. Antenna array algorithms are introduced as a possible solution to both these threats. Nevertheless, the performances of such techniques are degraded when considering technological defects and especially mutual coupling. To face this limitation, a HIS based antenna array design is presented. This design aims at minimizing the array mutual coupling coefficients while not increasing the size of the arra