Fresnel Zone and reflectarray antennas for space missions: Concepts, computational techniques and characterizations

Reflector antennas generally employ parabolic shaped main reflectors and have found a wide range of applications for both earth stations and satellite systems. Increasingly, one may find many advantages in minimizing antenna shaping requirement and weight as well as more compact designs by employing flat reflectors (either on the main reflector or on the subreflector) which can achieve a desired set of criteria for antenna performance. Two electrically large antennas which use flat min reflectors are Fresnel Zone (FZ) and reflectarray antennas which are being addressed in this dissertation. Analytical techniques are proposed, implemented, and verified to analyze these reflector geometries. A two dimensional (2-D) multi-scatterer analysis is formulated and implemented using various electromagnetic scattering techniques such as Physical Optics (PO), Method of Moments (MoM), and Geometrical Theory of Diffraction (GTD). The capability of the 2-D technique is further extended for dual reflector analysis with flat subreflector panels as well as design and analysis of FZ antennas with a proposed space missions application in solar sailing. FZ antenna design is based on establishing regions of quasi-uniform phases according to the PO current on the reflector face. The concepts extracted from the 2-D analysis of FZ reflectors is carried to the three dimensional (3-D) cases and incorporated into a multi reflector code, which has been widely used in variety of reflector applications. Like FZ antennas, reflectarrays work according to a similar set of principals by achieving a uniform phase current on the flat reflectarray surface. Accordingly, an analytical methodology is proposed and implemented within the structure of the multi-reflector code to analyze and give design criteria for both single and dual reflectarray configurations. This technique is compared to measured results published for single reflectarrays and is investigated for near-field Gregorian reflectarrays with beam scanning capabilities.