Improving the detection and estimation processes of acquisition module in Global Navigation Satellite Systems (GNSS)

摘要

Acquisition is the first task of any receiver used for positioning and navigation applications. The acquisition block of a GNSS receiver not only decides which satellite is present or not but also determines the carrier frequency and code phase of the satellite, if present. Therefore acquisition involves both detection and estimation processes, and it follows that the acquisition technique can be affected by factors involved in either detection or estimation processes. This paper discusses various factors that can be manipulated to improve the performance of the processes involved in acquisition. Digitized data at intermediate frequency (IF) was collected with a front end logger and was input to the software receiver. The software receiver implements different acquisition schemes by varying factors such as length of data, correlation time and number of blocks used for non-coherent integration. Factors related to the signal such as sampling frequency, IF and signal strength were also changed to analyze different acquisition schemes. The analysis provides a better understanding of the acquisition process and eventually leads to accurate and reliable positioning.