Dual-Band Low-Profile Crossed Asymmetric Dipole Antenna on Dual-Band AMC Surface

A dual-band, low-profile, circularly polarized antenna on an artificial magnetic conductor (AMC) is introduced in this letter. The antenna employs a single feed and two crossed asymmetric dipoles as the primary radiating elements. In order to achieve a low profile and broadband characteristics in terms of impedance matching and 3-dB axial-ratio (AR) bandwidths at both bands, a dual-band AMC is utilized as a reflector of the antenna. The AMC structure utilizes four T-shaped slits in a unit-cell patch to significantly reduce its first and second resonant frequency ratio, and consequently its first and second resonances are easily adjusted for the desired operating frequencies. For performance verification, an antenna prototype was fabricated with an overall 2.4-GHz frequency size of 0.576λ0 × 0.576λ0 × 0.088λ0 (72 × 72 × 11 mm3). The measurements resulted in impedance bandwidths of 2.20-2.60 and 4.90-5.50 GHz for 10 dB and 3-dB AR bandwidths of 2.30-2.50 and 5.05-5.35 GHz. Additionally, the antenna yields right-hand circular polarization and high antenna efficiency at both bands.