2.5-D Partially Reflective Surface for Resonant Cavity Antennas: Design and Synthesis

A new concept of 2.5-D partially reflective surface (PRS), with its potential applications in the design of resonant cavity antennas (RCAs), is presented. The proposed structure is in the form of a closed circular loop in which a pair of orthogonally split circular rings, printed on both sides of a substrate, is connected in series by four vertical vias to constitute the 2.5-D PRS unit cell. The 2.5-D PRS has a miniaturized unit cell size, in terms of wavelength, enabling the placement of a large number of unit cells in a given small area, and offers the flexibility of arranging those unit cells in different configurations. The unit cells are arranged in this work in a tapered configuration to construct the PRS. Based on the tapered 2.5-D PRS, a circular aperture RCA with an aperture area of <inline-formula> <tex-math notation="LaTeX">$2.04\lambda _{\mathrm {o}}^{2}$ </tex-math></inline-formula> (<inline-formula> <tex-math notation="LaTeX">$\lambda _{\mathrm {o}}$ </tex-math></inline-formula> being wavelength at the center frequency of 4.2 GHz) is designed, fabricated, and measured for its input reflection coefficient and radiation patterns. The prototype antenna yields a peak realized gain, 3 dB gain bandwidth overlapping with the impedance bandwidth, and an aperture efficiency, respectively, of 13.7 dBi, 26.2%, and 91.6%.