Radiation Characteristics of Differentially-Fed Dual Circularly Polarized GNSS Antenna

This paper discusses the method to create a dual circular polarized antenna for GNSS applications. First time, the differentially-driven circular patch is demonstrated to create a feasible cross-polarization discrimination (XPD) for phase accurate antenna structure. Traditional choke rings are applied to control the radiation pattern characteristics. A separate feed network is used to obtain simultaneous left and right hand circular polarizations for the corresponding coaxial connectors of the antenna. The operation of the feed network is described by using a block diagram. Resulting antenna radiation parameters include max. gain of 6.2 dB, axial ratio <; 3 dB over the upper hemisphere for the frequency range 1.55-1.61 GHz. The simulated antenna response for right hand polarized plane wave excitation demonstrate 27-29 dB isolation between the left and right hand antenna ports.