Low‐profile dual‐band dual circularly polarized patch antenna with small frequency ratio

Abstract

A dual-band dual circularly polarized (CP) patch antenna is proposed with low profile and small frequency ratio in this letter, which consists of a square patch, coupling lines, and a dual-feed network with dispersive delay line. Noticing that this antenna is fabricated on a single-layer substrate, thus acquiring low-profile performance. As for the coupling scheme, the bandwidth of impedance matching is increased to achieve dual-band radiation performance. On the premise that two orthogonal signals, which transmit in two paths of the dual-feed network, provide equal magnitude, the circular polarization can be controlled by the corresponding phase difference. Benefited from the dispersive delay line, the requirements of quadrature phases are met to present left−/right-handed circularly polarizations in two operating frequencies. Meanwhile, small frequency ratio can be easily achieved. To demonstrate the proposed design, the single-layer antenna with a profile of 0.006λ0 is designed, fabricated and measured. The phase difference of two orthogonal signals is adjusted to −90° at the lower operating frequency 1.9 GHz to realize right-handed CP characteristic, while 90° phase difference in two paths is achieved at the higher one 2.4 GHz to provide left-handed CP characteristic. Measured results are found in reasonably a good agreement with the simulated ones.