Effects of multipath and antenna on GPS observables

The authors present the analysis of effects on global positioning system (GPS) observables using the functional modelling and simulation package of a digital baseband processor for the GPS receiver. Three issues are addressed: first, the static observable errors as functions of multipath parameters are derived mathematically in the absence of input noise; secondly, the dynamic code and carrier tracking errors as functions of time due to multipath in the presence of input noise are investigated; and finally the deterioration in the accuracy of the GPS observables due to antenna residual phase and antenna centre movement is studied with different receiver design parameters. It is shown that the functional modelling and simulation package provide an alternative approach to GPS system accuracy research where theoretical analysis and hardware methods are very difficult, inaccurate or prohibitively expensive