COMPARATIVE-STUDY OF HIGH-PERFORMANCE GPS RECEIVING ANTENNA DESIGNS

The PAA decision allowing the use of the global positioning system (GP S) as a radio navigation and landing help system in the United States commercial airports boosts the need for a high-performance GPS receive r which provides the demanded precision, The design of the receiving a ntenna is one of the most important parts in the design process, as it has to face significant challenges including uniform coverage of all satellites and the rejection of the multipath signals. The rejection o f the multipath signals is accomplished by specifying restrictive crit eria to the GPS antenna, This includes a high rejection of the cross-p olarized signals and a radiation pattern with a sharp slope for low-el evation angles; that is, near the horizon, In this paper, the feasibil ity of using different types of antennas to satisfy restrictive criter ia such as dual-frequency coverage (L1 and L2 frequencies), -15 dB cro ss-polarization rejection, and a beamwidth of more than 130 degrees is discussed, The antenna designs examined in this study include patch a ntennas, helical antennas, and conical spiral antennas, Two different receiver designs were also examined including a single-antenna system with a hemispherical coverage and an antenna array which may provide i ndependent sectoral coverage of the desired beamwidth. It is shown tha t a design based on a conical spiral antenna backed with absorbing mat erial mag be used to satisfy all the desired specifications, This resu lt was confirmed experimentally.