Design and evaluation of wideband reflectarray antennas

Abstract

Reflectarray antenna is widely used in space and remote sensing applications, and acts as an alternative to a parabolic reflector and a phased array. In recent years, bandwidth enhancement of the reflectarray has drawn the attention of several researchers. This thesis presents studies on (a) the operational principle of a reflectarray; (b) several bandwidth enhancing elements; and (c) design, construction, and analysis of some wideband reflectarrays. A literature study showed that a smooth lens-loaded plane reflector antenna (SMLR) proposed by Kraus (1982) can be used as an alternative to the parabolic reflector. However, its experimental investigation has not yet been reported in the open literature. This thesis investigates a prototype of a SMLR antenna with the dimensions of 150 × 150 mm2 in the X band. Subsequently, a comparative study is carried out with a parabolic reflector and a microstrip reflectarray. In order to reduce the thickness of the above prototype, a reflectarray unit cell approach is employed to design a stepped-lens loaded plane reflector (STLR). The STLR is observed to have a reduction of 50% in its thickness in comparison with SMLR, without compromising on its radiation performance. The radiation patterns of STLR, SMLR, and microstrip reflectarray are studied and are found to be comparable with each other. Further, the main function of STLR and SMLR antennas is the phase compensation to the incident waves from the feed. Since a similar operation can be achieved using the reflectarray as well, a simulation-based study is carried out to examine if it can be considered equivalent to an artificial lens. The bandwidth enhancement of a reflectarray can be achieved by designing the elements appropriately. This is to ensure that they offer a smooth newline