A Spatial Signal Processing Review for Practical GNSS Antenna Arrays

The performance of an isolated antenna compared with itself but embedded (in-situ) in an array is not the same mostly due to the influence of mutual coupling and electromagnetic diffraction. Although signal processing techniques have been widely spread in literature for antenna arrays of elements with same physical properties and same performance, there is not enough mention regarding antennas with dissimilar behaviors. The usual way of avoiding this problem is by means of some kind of compensation that can reduce the differences but not always eliminate them, unless the information of the active radiation pattern of the antennas in array and wideband compensation techniques are used. A great advantage of employing adaptive methods for processing with antenna arrays is that it ensures good performance even without requiring this complete information. However, the distortions incorporated to the acquired signals by such processing step added to the improper characterization of the antenna array degrades the precision of the received signal parameters measurements. In this paper we analyze the need of using compensation techniques in GNSS applications when the performance of the array of antennas is properly characterized. The degrading effects of using adaptive antenna arrays on acquired GNSS signals and how to avoid them are also evaluated. Simulated results that involve an array of microstrip antennas for GNSS are presented.