Abstract
This paper presents a thorough review of the techniques involved in the enhancement of the efficiency performance of the reflectarray antenna. The effect of the selection of a suitable patch element or a proper feeding mechanism on efficiency improvement is studied in detail. Reflectarray loss quantification is examined in relation to the design techniques involved in the efficiency improvement. A low loss patch element with a wide reflection phase range and a properly illuminated reflectarray aperture are supposed to offer high efficiency performance. Additionally, the placement, the orientation and the position of a patch element on the reflectarray surface can also affect its efficiency performance. Mathematical equations were developed to estimate the efficiencies of circular and square aperture reflectarray antennas by considering their feed footprints. Moreover, a step by step practical method of predicting and measuring the total efficiency of a reflectarray antenna is presented. The two selected apertures of the reflectarray consisting of the square patch element configuration are fabricated and measured at a frequency of 26 GHz. Their measured efficiencies have been estimated using the derived equations, and the results were compared and validated using the efficiencies obtained by the conventional gain-directivity relation.
Highlights
The array of resonating elements used to reflect the incoming signals from a suitably placed feed, defines the basic architecture of a reflectarray antenna [1,2]
The aperture efficiency can be enhanced by optimizing the reflectarray feeding mechanism, which is related to the type and radiation characteristics of the feed
The shape and size of the reflectarray should coincide with the feed footprint to attain a maximum aperture efficiency
Summary
The array of resonating elements used to reflect the incoming signals from a suitably placed feed, defines the basic architecture of a reflectarray antenna [1,2]. One of the main reasons a reflectarray is preferred over a parabolic reflector is its ability to acquire electronic beamsteering with a comparatively small antenna profile [4] This could be done with a phased array antenna, but its design complexity is a major issue [17], which limits its progression towards millimeter waves. This is the main reason behind the higher gain performance of the parabolic reflector as compared to the reflectarray antenna.
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