Analysis of line-source-fed single-layer microstrip reflectarrays

Abstract

The analysis of scattering from an infinite periodic array of microstrip patches is used to study line-source-fed single-layer microstrip reflectarrays. An application of these reflectarrays is in high-gain conformal antennas. Employing rectangular patch geometries in the modelling, reflection phase properties of the reflectarrays are rigorously investigated. Effect of important parameters, such as, patch dimension, substrate permittivity and thickness, are examined. Included in the study is the effect of unattainable reflection phase on phase correction errors and far-field radiation characteristics. A formulation based on phased array and aperture theories is derived for the far-field analysis. For the analysis of an infinite periodic array of single-layer rectangular microstrip patches, an empirical expression is formulated for approximating the TE-to-z reflection coefficient phase with the incident angle. Also, for computing individual reflectarray far-field terms, simple symmetry formulations are presented. In addition, multiple patch geometries for the reflectarray are examined. A new hat-shaped patch geometry is introduced in combination with rectangular patch array, for enhanced performance. Far-field radiation characteristics, using tapered distribution schemes for line-source excitations, are compared with those of the uniform distribution. Subsequently, an offset-fed reflectarray is also proposed.