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 0.03λ0, 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.