3System Design and Aperture Efficiency Analysis

Design of a reflectarray antenna typically consists of two steps, namely, the phasing element design and the system configuration design. In the previous chapter, the analysis of phasing elements is presented, and this chapter focuses on the analysis of the reflectarray system configuration.

Usually, the system design begins with a specified gain requirement. Similar to traditional reflector antennas [1], [2], the gain of a reflectarray antenna is proportional to the electrical size of the aperture, and is calculated as the product of the aperture efficiency and maximum aperture directivity [3], [4]. Through the aperture efficiency analysis, one could estimate the required size of the reflectarray antenna aperture in order to achieve the desired gain. More importantly, it is desirable to design the system such that the aperture efficiency is maximized. Through the aperture efficiency analysis, one could optimize the parameters of a system configuration, such as feed specifications, f/D ratio, aperture shape, and so on. Hence, aperture efficiency analysis is critical in the system design.

In addition to aperture efficiency considerations, several other factors influence the system design, including feed blockage and edge taper. Feed blockage is generally minimized by offsetting the feed antenna, which usually decreases the aperture efficiency and increases the cross‐polarization. Typically, edge taper has to be kept below a certain ...

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