Comparative study of high performance GPS receiving antenna designs

A major factor in the performance of a differential Global Positioning System (DGPS) ground station is the performance of the antenna. The article analyzes and compares the performance of different GPS antenna designs. The specifications for the DGPS ground station antenna include hemispherical coverage and good multipath rejection. Good multipath rejection can be achieved by using an antenna that presents circular polarization and sharp drop-off at low elevation angles. In more detail, the specifications for the high precision GPS antenna include right hand circular polarization with a minimum of 15 dB of cross polarization rejection, hemispherical coverage presenting a variation of less than 3 dB over the main beam and a drop-off rate larger than 1 dB/deg for elevation angles from -5 to 5 deg. These specifications should be satisfied at the frequencies of 1.227 GHz and 1.575 GHz. The antenna designs examined in our study include patch antennas, helical antennas and conical spiral antennas. The numerical results from a successful conical spiral antenna design were verified experimentally.