Carrier Tracking Loop Improvement in a New Indoor Positioning System

The Carrier Phase Measurement (CPM) of GPS may achieve high precise location because of its short wavelength. While when a moving object comes into an enclosed area, GPS signal will be limited. For this paper, we propose a new indoor positioning model which aims to achieve cm-level indoor location by using CPM method. One of the most important parts of this model is to extract the most accurate carrier phase values from the tracking loop in receivers, thus the affection and performance of the carrier tracking loop will be firstly analyzed. The discriminator function is achieved by CORDIC algorithm based on hardware platform instead of traditional look-up-table method. The result shows that with the increasing iterations, carrier phase error can reach to 10^-7 rad which equals to the distance of 10^-6 cm and it has little impact on PVT. On the other hand, CORDIC algorithm saves hardware resources as well as has faster speed to process tracking loop.