Multi-Ring Unit Cells for Increased Phasing Range in Single-Layer Microstrip Reflectarrays

In this paper, we investigate planar antenna elements in the form of multi-rings of square and circular shapes, and explain the concept behind their increased phase range in a unit cell of a single layer microstrip printed reflectarray. It has been shown that the extended phase range can be obtained by utilizing similar in shape, but different in size, resonant elements. Using this principle it has been shown that two resonant elements forming a unit cell can double while three elements can almost triple the phasing range of a single resonant element unit cell, while the slope of the phase response remains almost unchanged. The issue of bandwidth improvement has not been considered. However, this can be achieved using thicker substrates similarly, as in the multi-layer approach.