Analysis and characterization of multilayered reflector antennas: rain/snow accumulation and deployable membrane

There are important engineering issues in designing reflector antennas that cannot be addressed by simply assuming a perfect electric conductor (PEC) reflector surface. For example, coatings may exist on antenna surfaces for protection, rain or snow can accumulate on outdoor reflectors, and the deployable mesh or inflatable membrane antennas usually do not have solid PEC reflector surfaces. Physical optics (PO) analysis remains the most popular method of reflector analysis owing to its inherent simplicity, accuracy, and efficiency. The conventional PO analysis is performed under the assumption of perfectly conducting reflector surface. To generalize the PO analysis to arbitrary reflector surfaces, a modified PO analysis is presented. Under the assumptions of locally planar reflector surface and locally planewave characteristic of the waves incident upon the reflector surface, the reflection and transmission coefficients at every point of the reflector surface are determined by the transmission-line analogy to the multilayered surface structure. The modified PO currents, taking into account by the finite transmissions of the incident waves, are derived from the reflection and transmission coefficients. Applications on the analyses of the rain and snow accumulation effects on the direct-broadcast TV antennas and the effects of finite thickness and finite conductivity of the metal coating on a 15-m inflatable antenna are described and results are presented.

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