Performance evaluation of shorted annular patch antennas for high-precision GPS systems

Even with the advances in signal processing, multipath error remains the major error source of high-precision global positioning system (GPS) applications. One of the most valid means to improve the accuracy of these systems is an appropriate design of the receiving antenna. Unfortunately, in many cases, the low-multipath-radiation requirements are very difficult to satisfy especially when physical constraints have also to be considered. As a possible solution, a study on the multipath rejection performances of shorted annular patch (SAP) antennas is presented here. In the first part, the SAP radiation characteristics will be deeply analysed by designing and testing three different antennas. Then, the results of a comparative test conducted on a GPS facility will be used to assess the on-field performances of the three prototypes. This experimental validation will show that a significant improvement of the SAP performances can be achieved when the reduced surface wave criterion, which has been widely adopted as a design rule in previous works, is relaxed and a trade-off between all the low-multipath-radiation requirements is considered. Moreover, comparison with two commercial GPS antennas will reveal that SAPs can be a very attractive and useful solution in high-precision GPS systems where severe physical constraints are imposed.