Decision Directed Adaptive Antenna Array for Operation in Low SNR Conditions

This paper presents an Adaptive Antenna Array (AAA) which is able to suppress the signals of the interferences at its output, to receive the informational signal under the low Signal-to-Noise Ratio (SNR) conditions and to steer its beam (the radiation pattern main lobe) towards the source of the informational signal even if the angular location of the source is initially unknown. It is presented the AAA architecture. The architecture is compared with other architectures of the AAA that are able or not able to operate under the same conditions. The ability to operate in low SNR condition is ensured because of the preprocessing of the AAA channel signals by the correlators or by the matched filters. Such preprocessing is possible if the received informational signal is a Pseudo Random Sequence (PRS). Using the signal as a desired one also allows to use the least squares criterion adaptive algorithms for the AAA weights calculation. This ensures the interferences suppression and the AAA beam steering simultaneously. The considered AAA is able to process the modulated PRS. This ability is provided by the usage of a slicer (like in a decision directed equalizer) which produces the desired signal from the AAA output signal during the steady-state operation. Two versions of the algorithms for the AAA weights calculations are presented. They are the Recursive Least Squares (RLS) adaptive filtering algorithms based on the inverse QR decomposition. Simulation results demonstrate the performance and the efficiency of the considered AAA.