Direction finding with compensation for electromagnetic effects

The effects of mutual coupling on several different direction finding algorithms are investigated. This is done by comparing the spectrum estimates with the ideal, actual, and corrected signals. The ideal signal assumes no mutual coupling is present while the actual signal includes all the effects of mutual coupling. It is shown that a terminal impedance representing the mutual coupling between the terminals of the array can be derived from the method of moments model of the array. This matrix is applied to the actual signal vector to produce the corrected signal without mutual coupling. These three signals are generated for various array geometries with various antenna elements. They are used to compute the spectra with the Beamformer algorithm, Capon's algorithm; the Linear Prediction algorithm and the MUSIC algorithm. The results show that the mutual coupling has an adverse effect on the resolution capability of the super resolution algorithms and that its effects can be virtually eliminated from the spectra by pre-processing the signal with the terminal impedance matrix.; The effects of a near field scatterer on the spectrum generated from the MUSIC algorithm are also investigated. It is demonstrated that a near field scatterer significantly reduces the resolution capability of the MUSIC algorithm. This is accomplished with a linear array and near field scatterer modeled using a hybrid technique that combines the Method of Moments and the Uniform Theory of Diffraction. The effects of the scatterer are compensated for using a modified terminal impedance matrix, a new array configuration, and a modified search vector. Results are presented for various scatterers. It is shown that the terminal impedance matrix and the new array configuration can be used to almost completely suppress the effects of a near field scatterer.; Finally, the terminal impedance matrix is applied to actual measurements to compensate for the effects of mutual coupling. The terminal impedance matrix is also applied to an array of horn elements. In this case, a new technique for calculating the terminal impedance matrix from only measurements is presented. It is then used to compensate for the effects of mutual coupling.