Dual frequency circularly polarised antennas and arrays for satellite navigation

Antennas are described which are designed for reception of GPS signals at 1575 MHz and 1227 MHz from a number of satellites scattered across the upper hemisphere. The dual frequency microstrip crossed slot antenna is described, and its performance presented. The phase distribution network can be designed with or without isolation resistors, and these two approaches are compared. The performance of a seven element adaptive array of these elements is described. The isolation of the distribution network is shown to be particularly important for the adaptive array