Compact dual-polarized VHF microstrip antenna for satellite applications

This paper presents the design of a compact dual-polarized VHF microstrip antenna for modern small satellites. It consists of a slot-loaded annular-ring microstrip antenna printed on a light substrate to reduce its mass. A simple matching circuit is proposed to match the high input impedance of this antenna while enabling the generation of a dual linear-polarization. The size of the proposed design is finally equal to 450 mm at 161 MHz, i.e. y0/4

Non Data Aided Parameter Estimation for Multi-User ARGOS Receivers

In this paper, parameter estimators are analyzed in the context of Successive Interference Cancelation (SIC) receivers for the ARGOS system. A Non Data Aided (NDA) feed forward estimator is proposed for the amplitude and the carrier phase parameters. Time delays are assumed to be known. A Window Accumulator (WA) is used to reduce the influence of the additive noise. In the presence of frequency offset, the window length L cannot be chosen arbitrarily large but an optimal length Lopt can be determined. However, because the estimator induces a different optimal length for each parameter, a trade-off must be made. We show that a window length of around 35 samples induces mean square errors (MSEs) lower than 0.012 for both parameters. The MSE of the proposed estimator is also compared to the Modified Cram´er Rao Bound (MCRB)

Multiuser Detection For Asynchronous ARGOS Signals

In this paper, we investigate the application of multiuser detection techniques to a Low Polar Orbit (LPO) mobile satellite used in the ARGOS system. These techniques are used to mitigate the multiple access interference in the uplink transmission of the system. Unlike CDMA, due to the Doppler Effect, each signal has a different received carrier frequency and a different propagation delay. Multiuser detection techniques are proposed for asynchronous transmission in ARGOS system: the maximum likelihood detector, the conventional detector, and the sequential interference cancellation detector, as solutions to tackle the interference effects. Bit Error Rate performance graphs are shown for these techniques

Impact of Imperfect Parameter Estimation on the Performance of Multi-User ARGOS Receivers

In this paper, we analyze the performance of Successive Interference Cancelation (SIC) receivers in the context of the ARGOS satellite system. Multi-user SIC receivers are studied in presence of imperfect estimates of signal parameters. We derive performance graphs that show the parameter ranges over which a successful demodulation of all users is possible. First, the graphs are derived in the context of perfect parameter estimation. Then, imperfect parameter estimation is considered. Erroneous estimations affect both the amplitude and the time delay of the received signal. Carrier frequencies are assumed to be accurately measured by the receiver. ARGOS SIC receivers are shown to be both robust to imperfect amplitude estimation and sensitive to imperfect time delay estimation

Multiuser detection for time synchronous ARGOS signals

Multiuser detection has recently been a big challenge in the increase of the performance for a satellite communication system. In the previous studies on systems such as CDMA, researchers have derived general mathematical expressions to describe the system model. However, when it comes to specific system such as ARGOS system, solutions based on general expressions may no longer be valid and thus new mathematical derivations could be formulated. In this paper, we propose a new mathematical model for synchronous multiuser communication in ARGOS system and we analyse the performance of the optimum multiuser detector and some sub optimum techniques such as conventional, decorrelator, Minimum Mean Square Error, and successive interference cancellation detectors

Bornes de Cramér-Rao modifiées pour le temps d'arrivée et la période symbole. Application aux signaux de recherche et de sauvetage

National audienceCet article étudie la performance des estimateurs de temps d’arrivée de signaux de détresse qui sont définis par des formes d’onde ayant des transitions douces. Ces signaux sont utilisés dans le système de recherche et sauvetage par satellite Cospas-Sarsat. Nous proposons un modèle de signal basé sur des transitions sigmoïdales. Des expressions analytiques des bornes de Cramér-Rao modifiées associées aux paramètres de ce modèle sont déterminées. Les expressions obtenues sont faciles à interpréter, car elles dépendent analytiquement des paramètres du système. Des simulations effectuées avec des signaux réalistes concordent avec les résultats théoriques

Modified Cramér-Rao lower bound for TOA and symbol width estimation. An application to search and rescue signals

International audienceThis paper focuses on the performance of time of arrival estimators for distress beacon signals which are defined by pulses with smooth transitions. These signals are used in the satellite-based search and rescue Cospas-Sarsat system. We propose a signal model based on sigmoidal functions. Closed-form expressions for the modified Cramér-Rao bounds associated with the parameters of this model are derived. The obtained expressions are easy to interpret since they analytically depend on the system parameters. Simulations conducted on realistic search and rescue signals show good agreement with the theoretical results

Modified Cramér-Rao lower bound for TOA and symbol width estimation. An application to search and rescue signals

This paper focuses on the performance of time of arrival estimators for distress beacon signals which are defined by pulses with smooth transitions. These signals are used in the satellite-based search and rescue Cospas-Sarsat system. We propose a signal model based on sigmoidal functions. Closed-form expressions for the modified Cramér-Rao bounds associated with the parameters of this model are derived. The obtained expressions are easy to interpret since they analytically depend on the system parameters. Simulations conducted on realistic search and rescue signals show good agreement with the theoretical results