Enhanced Detection of Weak GNSS Signals Using Spatial Combining

Detection of global navigation satellite systems (GNSS) signals is limited in indoor environments due to signal attenuation and multipath fading. Longer signal integration intervals are traditionally used to overcome fading losses. Another possibility, explored herein, is to use spatial combining of multiple antenna ele- ments to provide both array and diversity gain. Physical constraints of handheld device implementation limit the practical number of antennas to two. Consequently in this paper, the diversity gain achievable through spa- tial combining of a pair of antennas is considered from a theoretical perspective, demonstrating gains in excess of 6 dB for typical cases. Experimental verification of the theoretical predictions of the processing gain is pro- vided based on a two-element antenna configuration. Indoor GPS signal measurements were made to determine the statistics of the diversity gain of the two-antenna system relative to the equivalent single antenna system. These measurements corroborate the relative diversity gains determined theoretically.