Research on adaptive antenna techniques 6

Signal cancellation is an effect which occurs in conventional adaptive arrays. This effect manifests itself as a loss of information in the desired signal. This presents two new adaptive array techniques to combat signal cancellation. These two techniques are known as the frequency-hop spread spectrum approach and the parallel spatial processing approach. The frequency-hop spread spectrum technique makes use of frequency-discrimination to combat jammer interference. Using the desired signal's frequency-hop nature, we can remove the signal from the adaptation process in a manner that eliminates signal cancellation. When the spread-spectrum technique and the spatial-discrimination inherent in adaptive arrays are combined, a system results with an interference rejection capability greater than either of the two alone. Several effective schemes and simulations are presented. The second technique makes use of spatial smoothing and parallel structure to eliminate signal cancellation. We show that this new scheme results in a maximum-likelihood estimate of the desired signal in a spatial averaging sense. Simulation results are presented to illustrate the effectiveness of this proposed technique for combating signal cancellation.