Circularly‐polarized cavity‐backed slot antenna array with simplified feeding structure

Abstract

A class of circularly-polarized cavity-backed slot antenna arrays with simplified feeding structure are proposed. Power dividing network is an essential feeding structure for the design of conventional antenna arrays, which results in complicated antenna structure. A novel feeding technique based on the electric field of cavity modes is introduced to feed the array elements. The slots on the top wall are directly fed by the electric field without additional feeding structure. Crossed slots with different lengths are introduced to achieve the self-phased CP radiation as they produce different perturbation on the two degenerate cavity modes. Therefore, high efficiency and simple antenna structure of the CP slot antenna array are achieved. Then, two CP slot arrays with 3 Â 3 and 8 Â 8 elements are presented to show the designed feasibility. Finally, the 3 Â 3 CP antenna array is fabricated and measured to validate the design concept, which can achieve 12.6 dBic gain, 94% total efficiency, 80% aperture efficiency, and À25 dB cross polarization. K E Y W O R D Scavity-backed slot antenna arrays, circularly-polarized, crossed slots, high efficiency, simplified feeding structure | INTRODUCTIONCavity-backed slot antenna (CBSA) is a good candidate for the high-efficiency and high-gain wireless communication systems. SIW CBSAs designed in References 1-3 have low profile and low cost, but has low efficiency produced by dielectric loss. The air-filled SIW 4,5 can reduce the dielectric loss, which can be used to design efficiencyenhanced slot antennas. 6,7 In general, due to the involvement of the substrate, air-filled SIW slot antennas still have relatively lower efficiency compared with the fullmetal slot antennas. [8][9][10] Besides, full-metal slot antennas are highly demanded in high-power communication systems for their high power-handling capacity.Circularly polarized antennas are widely used in satellite and radar communication systems to reduce polarization mismatch and multi-path interference. The degenerate modes is a widely-used method to design CP antennas, [11][12][13][14][15][16][17][18][19][20] including CP patch antennas, [11][12][13][14] CP SIW slot antennas, 15-19 and metal cavity slot antenna. 20 This