Research on adaptive antenna techniques 2

The concept of adaptive power separation for single channel applications based on the 'leaky' LMS algorithm has now been extended for adaptive array applications. A new algorithm designated as 'scheme 6A' has been shown to be potentially highly effective for nulling strong jamming signals in an aircraft receiving environment. The new scheme is substantially less noisy and more simple to implement than 'scheme 6' which was analysed during our previous year's effort. All real-time adaptive processes experience noise in the adaptive parameters. The amount of noise depends on the nature of the adaptive algorithm, on the number of parameters, and on the speed of convergence. A fundamental study of parameter noise and its effects on the output signal has been undertaken for stochastic and deterministic inputs to weight-controlled adaptive filters driven by the leaky LMS algorithm. Weight noise has been determined for the case of an input consisting of a sinusoidal signal plus white noise, for wide ranges of SNR and frequency relative to Nyquist. Broad operating regions have been found where the output power due to weight noise is less than 5% of the output signal power.