Adaptive Antenna Array for Low Signal-to-Noise Ratio Operation

The adaptive antenna array which operates in the low signal-to-noise ratio (SNR) is presented. In this scenario, the Minimum Mean Squares Error (MMSE) criterion adaptive algorithms cannot be used for the array weight calculation. If the angular location of the signal source is known, it is possible to use the linearly constrained adaptive algorithms. However, this location is often unknown or it is changed if the signal source or the array is moving. At the same time, if the informational signals are the pseudo-noise sequences, they can be pre-processed by the matched filters or by the correlators. In this case the informational signal at the devices output becomes above the noise (the SNR is increased) and the MMSE criterion algorithms can be used for the calculation of the adaptive array weights. The adaptive array based on this criterion is able to suppress the interference signals. Besides, it is also able to steer the beam in the direction of the informational signal source and to track the source. The computational procedures of the two Recursive Least Squares algorithms which process the matched filter output signals for the calculation of the adaptive array weights are considered. One of these algorithms uses the complex-valued arithmetic and other one uses the real-valued arithmetic. The simulation demonstrates that the real-valued arithmetic algorithm has about 3 dB better cancellation of the interference signals at the adaptive array output and about two times shorter transient response.