RF Multipath Estimation in GPS signals using Dual Polarised Antenna(DPA)

Simulation Models for GNSS Receiver RF Multipath and Interference Estimation with Dual-Polarization Antenna (DPA) TITLE: RF Multipath Estimation in GPS signals using Dual Polarised Antenna(DPA) The GPS signals travelling through the space come across various phenomena before reaching the receiver. Multipath, one of these effects, indicate the situation when the GPS signals propagating towards the receiver undergo reflection on the ground or surrounding objects and reach the receiver not only through one path but also these secondary components. This causes the receiver to receive the Line Of Sight (LOS) signal along with the reflected version of the signal which arrives with a certain amount of delay. This results in error in the pseudorange estimation. The composite signal received due to the multipath has various characteristics in terms of amplitude, polarisation, phase and so on. These characteristics mainly depends on the kind of the reflecting material that the signal came across. This thesis focuses on the study of the GPS L1CA signals received using a receiver with Dual Polarised Antenna (DPA). Apart from the dual antenna another feature of the receiver is the presence of 11 multicorrelators instead of conventional Early - Late correlators. In particular, the signals processed in the thesis work were acquired in the premises of ESTEC, Noordwjik, Netherlands. However, the entire work of the thesis is performed in Thales Alenia Space Italia, Gorgonzola, Milan. In this thesis a multipath signal model is developed for the signals received by both the Right Hand Circular Polarisation (RHCP) and Left Hand Circular Polarisation (LHCP) chains of the receiver. The In phase-(I) and Quad-phase-(Q) components of all the 11 multicorrelators received from both the RHCP and LHCP chains are analysed and processed to see the nature of the signal received. After various considerations the signals (multicorrelator observables) are fed into the Extended Kalman Filter (EKF) which is used to estimate the necessary multipath parameters. The performance of the EKF in parameters estimation depends upon the correctness of the model developed to represent the signals and states to be estimated. The main focus of this work is to be able to characterise the multiipath signal better by taking the advantage of both RHCP and LHCP sensed polarisations. Along with the conventional EKF, the multicorrelators observables are also processed for multipath parameters estimation using a constrained version of the EKF. Various charts depicting the Kalman filter estimates like LOS amplitude, delay and phase, multipath amplitude, delay and phase for both the RHCP and LHCP side are generated and presented in the thesis. Statistical characterisation of various figures of merits like the D/U (ratio between desired and undesired signals) and the ratios between RHCP and LHCP multipath componenets with respect to the RHCP and LHCP LOS signal components is done by generating several histograms. The presence of multipath was detected at some instants in the database through the estimation done using EKF.