Abstract: A gamma feed microstrip antenna for a Doppler navigation system includes a forward firing feed parallel spaced to a backward firing feed. A plurality of parallel spaced radiating arrays are transversely connected between the feeds. Each array includes radiating elements of preselected sizes having radiating coefficients and coupling coefficients to the feeds whereby an amplitude function of the antenna along the axis of travel is a truncation of a long slanted array amplitude function. Sequential excitation of four input ports at the ends of the feeds causes sequential generation of four beams. Return signals to the antenna, at the four input ports, may be sampled and held for averaging. This antenna structure is adapted for use to as to provide frequency, temperature and over-water corrections.

Abstract: An apparatus and a method for achieving simultaneous circular polarization of a four-beam doppler antenna wherein four different grid layers are positioned into a radome. The first grid layer, besides radiating a linear polarized beam, is used to partially reduce contaminants of the linearly polarized beam by means of cross-hatch strips. The second grid layer is used to further purify the linear polarized beam such that an essentially purified linear polarized beam is obtained. The third grid layer, designed according to certain equations, is used to convert the purified linearly polarized beam into a partially circularly polarized beam. And the fourth grid layer is used to make sure that the circularly polarized beam is perfectly matched.