Dual Circularly-Polarized Equilateral Triangular Patch Array

Abstract—This paper presents a novel sequentially rotated patch array antenna with dual circular-polarizations (CP). The present design has the advantages of compact size, simple feed networks, low cross-polarization and high isolation. The radiating elements are dual linearly-polarized (LP) equilateral triangular patches with hybrid feeds. The vertical polarization of the patch antenna is obtained by using an aperture-coupled feed and the horizontal polarization is obtained by using a proximity feed. These two feeds are orthogonally positioned and are printed on different PCB layers, which leads to the high isolation between these two ports and facilitates the design of the feed networks. The array antenna consists of six such dual-LP triangular patches sequentially rotated by 60o and fed by separated feed networks. Since linearly polarized antenna elements are used, the design of the feed network is much simplified. Through sequentially varying the feeding phase by ?60o, dual circular-polarizations are obtained. The operation principle of the array antenna is also analytically explained in this paper. To verify the design concept, one dual LP equilateral triangular patch and one dual CP equilateral triangular patch array resonating at 10.5 GHz are designed, fabricated and tested. There is a good agreement between the simulation and measurement results, both of which show that the array antenna exhibits high port isolation and good circular polarizations with low cross polarization at different planes. The proposed design technique can be applied to the design of dual CP array antennas operating at other frequency bands. Index Terms—dual circular polarization, sequential rotation, microstrip, hybrid feed, high isolatio