Another subspace-based DoA high resolution technique suffers from the spatially limited radiation pattern of the is the ESPRIT. It reduces the computational requirements array elements. By using spherical arrays, there will significantly when compared with MUSIC as an extensive always be some elements radiating into the direction of search through all possible steering vectors is not needed. A the signals, hence increasing the signal-to-noise ratio of practical implementation of the ESPRIT is made in the subsequent digital processing. To minimise the cou- [BHHTO4b], where the spatial scanning is configured to pling and hence to increase the decorrelation between all resemble an antenna array, also called a synthesised the antenna elements, they should be spaced uniformly Propagation modelling and channel characterisation CHAPTER 4.7 over the sphere. This configuration will also increase the measurements with a Mill's cross antenna array, resulting resolution of the antenna array. in better extraction results of the measurements. Of course, using different antenna elements causes In most measurements, not only the type of antenna, the radiation from one element to couple to its neigh- but also the position and the polarisation of the antenna bours. The real current on each array element is the sum array, are very important. By taking into account both of the values due to the excitation plus all contributions position and polarisation in the radiation pattern of an from the various coupling sources from each of the antenna array, another adaptation to the commonly used neighbours. This mutual coupling is in most cases not time domain SAGE algorithm is made. Hence the desired, but will often be a significant factor in the total direction-of-arrival parameters can be determined very radiation characteristics. In [VeLC02a], this mutual accurately. Simulation results with a cubical or hexahedral coupling is integrated in the SAGE algorithm and the antenna array are shown in [LVTC04]. Results with a convergence and per