A Wideband Resonant Cavity Antenna Assembled Using a Micromachined CPW-Fed Patch Source and a Two-Layer Metamaterial Superstrate

This paper reports the development of a wideband resonant cavity antenna (RCA). The RCA device was obtained by using an optimized aperture-coupled coplanar waveguide fed wideband patch antenna and a metamaterial-based superstrate design. The wideband behavior is based on the effects of Fabry–Perot cavity on either side of the resonant frequency of the metamaterial superstrate and the finite size of the superstrate to obtain enhanced gain around this frequency. In addition, the metamaterial superstrate in this paper contains two identical layers of a frequency selective surface (FSS) based on a 2-D patch array rather than dissimilar arrays as used in the previous studies. Two such FSS layers are assembled using a laser micromachined polymethyl methacrylate rim and an SU8-based bonding method. The air spacer based metamaterial design offers better performance by minimizing the dielectric loss between the metallic patch arrays and also offers flexibility in the control of the separation between the two FSS layers as well as resulting in a lightweight RCA device. The RCA device was designed to operate in the X-band. The dimensions of the compact RCA device are $45\times 45\times24$ mm3. The gain of the device was measured to be ~13 dBi with a 3-dB bandwidth of 46% and a corresponding 1-dBi-ripple bandwidth as wide as 40%. The measured impedance bandwidth was 44%.