A Low-Profile Dual-Band Dual-Mode and Dual-Polarized Antenna Based on AMC

A low-profile dual-band dual-mode and dual-polarized (DBDMDP) antenna based on artificial magnetic conductor (AMC) is presented in this letter. One reference antenna made of a pair of double-printed crossed dipoles employing vacant quarter-rings is originally realized with dual-band dual-polarized property but strong back radiation. Then, one square-shaped AMC layer is used instead of the metal ground with improved performance. For the lower mode (at 1.38 GHz), the AMC reflection phase of 90° is employed to change the electromagnetic field distribution and achieve monopole-like omnidirectional linear polarization (LP) radiation. Meanwhile for the higher mode (at 1.57 GHz), the AMC with reflection phase of 0° is regarded as a reflector to realize patch-like unidirectional circular polarization (CP) radiation. Thus, probe-single-feed DBDMDP antenna is realized with low-profile property of 0.03λ
₀
, as well as pattern and polarization diversity. One prototype is fabricated to verify the theory analysis, and the measured results reveal that the maximum gain is higher than 2 dBi and 7 dBic for the LP omnidirectional and CP unidirectional modes, respectively. With the advantages of low profile and multifunction, this method offers a good candidate for global position systems applications in the future.