Artificial magnetic surface for circular polarization improvement

A novel approach to improve the circular polarization properties of a small elliptically polarized (EP) radiating element is presented. The enhancement in circular polarization is obtained by mounting the radiating element close to an artificial magnetic conductor (AMC). To explain the antenna operating principle, two different typologies of radiating element have been initially considered, i.e., a small spiral antenna and a dipole. Both antennas are EP, but the excited current distribution on the AMC screen are circular and linear, respectively. We inferred that only a circular current distribution determines the XPD improvement in correspondence of the AMC resonances. The prototype of the small spiral antenna in the vicinity (λ0/18) of the AMC screen has been manufactured and tested. Measurements confirmed a remarkable improvement in spiral cross polarization discrimination (XPD) in correspondence of the two AMC resonances. The dual‐band behavior of the AMC could be exploited in applications where multifrequency operation is required. The low profile structure is characterized by an overall thickness of 1.1 cm, which corresponds to ∼λ0/12 at the centre of the operating band. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1782–1786, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25345