The article is devoted to obtaining equivalent forms of writing of processing algorithms for the operation of adaptive antenna arrays, considering algorithms as varieties of some generalized LMS algorithm. This will facilitate a comparative analysis of the algorithms' characteristics. The following algorithms of operation are considered: LMS, NLMS, LMS-Newton, SMI, RLS. The article contains the initial operation algorithms of adaptive antenna arrays, conclusions of equivalent processing algorithms and an equivalent block diagram of the generalized LMS algorithm. Equivalent forms of writing the operation algorithms of adaptive antenna arrays and their parameters are also presented in tabular form. Of particular interest is the equivalent operation algorithm in the case of the SMI algorithm, which differs most from the LMS algorithm. Equivalent algorithms differ only by the scalar convergence coefficient and the matrix normalizing factor. For LMS-Newton, SMI, and RLS algorithms, the matrix normalizing factor is the same, it is determined by inverting the estimation of the correlation matrix of input signals and reduces the dependence of the characteristics of the algorithms on the parameters of the correlation matrix. The scalar convergence coefficient of equivalent algorithms in the case of SMI and RLS algorithms depends on the iteration number and tends to zero for the SMI algorithm and to some non-zero value for the RLS algorithm. The dependence of the convergence coefficient on the iteration number makes it possible to optimize the characteristics of the algorithms at the transition stage. The tendency of the convergence coefficient to zero in the case of the SMI algorithm makes it effective only for stationary input signals. The non-zero steady-state value of the convergence coefficient in the case of the RLS algorithm allows its effective use in a non-stationary environment.
Navigation by satellite systems are known to be susceptible to jamming threats. This thesis explores adaptive array techniques as a solution to the military signals (GPS & Galileo) vulnerability to broadband powerful jammers. The array and the receiver are positioned in a cascade structure. The goal is to make the array autonomous and fully compatible with a classical receiver, which rapidly led us to focus on MISO systems. Several algorithms have been evaluated and compared over various array geometries. We pointed out that the mean array output SINR is not an appropriate criterion to characterize the receiver performances in the particular case of radionavigation systems. Thus, we define a new criterion based on the final user positioning accuracy. We subsequently demonstrated that using prior knowledge of the useful DOA does not necessarily help with improving this criterion with MISO systems. The array response stability was also studied, leading us to finally focus on blind linearly constrained power minimization techniques. Then we described the main RF technological defects (due to manufacture dispersions in sensors and analogical filters and due to mutual coupling). Their effect on space-only array performances was evaluated. Physically, and similarly to the wideband effect, these defects result in an increased number of degrees of freedom of the array required to mitigate a single powerful jammer. Space Time array (STAP) is a possible solution to cope with the increase in the interference subspace rank because it makes it possible to increase the number of degrees of freedom available without increasing the physical size of the array. In such a case, the frequency component of the STAP filter is likely to degrade the performances of a classical GNSS receiver's correlator. Hence, we defined a new performance criterion, suitable for GNSS signals after STAP prefiltering. Then, we synthesized the optimal filter according to this criterion, and we derived a simplified version which results in a good ...
Navigation by satellite systems are known to be susceptible to jamming threats. This thesis explores adaptive array techniques as a solution to the military signals (GPS & Galileo) vulnerability to broadband powerful jammers. The array and the receiver are positioned in a cascade structure. The goal is to make the array autonomous and fully compatible with a classical receiver, which rapidly led us to focus on MISO systems. Several algorithms have been evaluated and compared over various array geometries. We pointed out that the mean array output SINR is not an appropriate criterion to characterize the receiver performances in the particular case of radionavigation systems. Thus, we define a new criterion based on the final user positioning accuracy. We subsequently demonstrated that using prior knowledge of the useful DOA does not necessarily help with improving this criterion with MISO systems. The array response stability was also studied, leading us to finally focus on blind linearly constrained power minimization techniques. Then we described the main RF technological defects (due to manufacture dispersions in sensors and analogical filters and due to mutual coupling). Their effect on space-only array performances was evaluated. Physically, and similarly to the wideband effect, these defects result in an increased number of degrees of freedom of the array required to mitigate a single powerful jammer. Space Time array (STAP) is a possible solution to cope with the increase in the interference subspace rank because it makes it possible to increase the number of degrees of freedom available without increasing the physical size of the array. In such a case, the frequency component of the STAP filter is likely to degrade the performances of a classical GNSS receiver's correlator. Hence, we defined a new performance criterion, suitable for GNSS signals after STAP prefiltering. Then, we synthesized the optimal filter according to this criterion, and we derived a simplified version which results in a good compromise between performances and complexity. Finally, STAP cannot help to improve the useful signal power but it helps with better nulling strong broadband interferences even when linear technological defects are present. ; Les systèmes de navigation par satellite sont connus pour être sensibles aux interférences. Cette thèse étudie les techniques d'antennes adaptatives comme une solution au problème du brouillage des signaux militaires (GPS et Galileo) par des interférences de forte puissance et à grande occupation spectrale. L'objectif est de réaliser, à terme, une antenne réseau indépendante du récepteur de radionavigation, ce qui nous a rapidement conduit à privilégier les systèmes MISO. Divers algorithmes de traitement ont été évalués sur plusieurs géométries de réseau. Nous avons mis en évidence que le SINR moyen de sortie du réseau n'est pas représentatif des performances d'un récepteur de radionavigation. Un critère de sélection des méthodes, basé sur la précision finale de localisation, a donc été défini. Nous avons montré que, selon ce critère, la connaissance a priori des DOA ne permet pas forcément de gain de traitement avec un système MISO. La stabilité de la réponse des réseaux a également été étudiée, nous conduisant finalement à restreindre notre étude aux méthodes aveugles de minimisation de puissance sous contrainte linéaire. Nous avons ensuite caractérisé les principaux défauts de la chaîne RF (dus aux dispersions de fabrication des capteurs et des filtres analogiques, et au couplage inter-capteurs) et en avons évalué l'impact sur les performances des filtres spatiaux. Physiquement, comme l'effet large bande, les défauts du réseau se traduisent par une augmentation du nombre de degrés de liberté consommés par un signal de forte puissance. Le traitement Spatio-Temporel (STAP) constitue une solution possible à cette augmentation du rang du sous-espace interférent car il permet d'accroitre le nombre de degrés de liberté disponibles, sans augmenter la taille du réseau. Cependant, la composante fréquentielle du filtrage STAP peut dégrader les performances du corrélateur d'un récepteur GNSS générique. Aussi, avons-nous défini un nouveau critère de performance, adapté au traitement des signaux GNSS. Nous avons ainsi pu écrire le filtre STAP optimal et nous en avons déduit une version simplifiée qui constitue un bon compromis performances - complexité. Globalement, le réseau STAP ne permet pas de gain de traitement sur la puissance utile transmise au récepteur mais il permet de mieux rejeter les signaux interférents de forte puissance en présence de défauts linéaires de chaîne.
Around the early 1900's, the first transmission of radio waves by means of phased array antennas was demonstrated. Since then, the further development of phased array radars was largely driven from a military point of view, with operational phased array systems implemented as far back as the second World War. In recent times, phased array antenna systems have become much more prevalent, not only in a military context but also increasingly in the commercial space, with array antenna implementations used in satellite communication systems and direction finding systems around the world. With this in mind, the following dissertation presents the development, functionality and results of a phased array simulation toolbox developed in the open source programming language, Julia. Some of the main concepts demonstrated in this dissertation include various array antenna configurations, including linear, planar, circular, cylindrical, spherical and conical, each of which are customisable in terms of beam steering, number of array elements, inter-element spacings and in some cases, array tapering to name but a few. The aim behind the development of the array toolbox is to provide array antenna enthusiasts and students with a simple to use simulation package, enabling an investigation into the effect of various array antenna parameters on the output antenna pattern produced
The design of the elliptical antenna arrays is relatively new research area in the antenna array community. Backtracking search optimisation algorithm (BSA) is employed for the synthesis of elliptical antenna arrays having different number of array elements. For this aim, BSA is used to calculate the optimum angular position and amplitude values of the array elements. BSA is a population-based iterative evolutionary algorithm. The remarkable properties of BSA are that it has a good optimisation performance, simple implementation structure, and few control parameters. The results of BSA are compared with those of self-adaptive differential evolution algorithm, firefly algorithm, biogeography based optimisation algorithm, and genetic algorithm. The results show that BSA can reach better solutions than the compared optimisation algorithms. Iterative performances of BSA are also compared with those of bacterial foraging algorithm and differential search algorithm.
