A Circular Polarization Selective Surface Made of Resonant Helices,
DEFENCE RESEARCH ESTABLISHMENT OTTAWA (ONTARIO)
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A circular polarization selective surface CPSS is a surface that reflects one sense of circular polarization but transmits the other sense. While linear polarization selective surfaces usually abbreviated PSS are fairly common, CPSSs have attracted attention only recently. In this report, a new CPSS with improved characteristics is presented and potential applications are discussed. This new CPSS is made of special square helices. Because the helices can be supported at their extremities, this CPSS does not need a dielectric support as other CPSSs do and therefore can be made more transparent. The response of the CPSS to a plane wave excitation was simulated using the method of moments for thin wires. Mutual coupling and losses were taken into account. Simulation results show that the radar cross section of the surface to one circular polarization is 50 times higher than to the other polarization. A CPSS has been fabricated. Transmission measurements show that the surface permits most of one circular polarization to pass through while rejecting the other polarization. The rejection ratio is more than 15 dB. These results are in good agreement with the theory. Three potential applications of CPSSs in the field of reflector antennas are reduction of sub-reflector blockage in dual reflector antennas, frequency reuse through polarization diversity in a dual-offset reflector, and design of a mirror antenna for circular polarization.
- Radiofrequency Wave Propagation