Multipath Mitigation Techniques for GPS

We propose to develop two unconventional techniques to estimate multipath signals and to mitigate their effects on GPS code and carrier measurement accuracy. These two techniques can be applied separately and/or in combination to individual GPS signals and/or to several GPS signals jointly. The first technique will make use of a dual circularly polarized antenna from which the RHCP signal will be used for normal operation while the LHCP signal is for multipath estimation. With a slight increase in hardware, the multipath signals can be strengthened by 10dB. This is significant to obtain more accurate estimation of closely spaced multipath signals. The second technique will estimate the multipath parameters in the frequency domain. This frequency-domain formulation is equivalent to the time-domain deconvolution but it transforms the problem of estimation with nonlinear functional equations in the time domain into one with linear parametric equations in the frequency domain, thus greatly facilitating the solution process. In Phase I, the proposed system concept will be refined and the enabling algorithms developed. We will perform a preliminary design of hardware subsystems and characterize the algorithms performance by means of analytic study and numerical simulation. In Phase II, the recommended architecture and the validated algorithms will be implemented in a breadboard prototype for demonstration.