Fundamental Limitations of Focal Plane Arrays Characterized in Terms of Radiation Efficiencies of Their Embedded Element Patterns

This paper investigates the prospects of using an array of open-ended miniaturized rectangular hard waveguide elements to realize a dense focal plane array (FPA) feed illuminated according to the desired Airy-disc aperture illumination function. The investigation employed an existing computer program code that analyzes an infinite planar "active" array of such open ended dielectric-loaded hard rectangular waveguides which are uniformly excited and linearly phase-steered to give a certain beam direction. Upon further processing and manipulation of the results generated by this array code, any kind of array aperture illumination (in both amplitude and phase) can be studied, with all self and mutual coupling effects taken into account. Hence, this permits the study of the Airy-illuminated FPA feed. The objective of this paper is to ascertain the effects of element size on radiation efficiency of the FPA feed