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 CPW (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 obtained enhanced gain around this frequency. In addition, the metamaterial superstrate in our work contains two identical layers of a frequency selective surface (FSS) based on a two dimensional patch array rather than dissimilar arrays as used in the previous studies. Two such FSS layers are assembled using a laser micromachined PMMA rim and a 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 control of the separation between the two FSS layers as well as resulting in a light weight RCA device. The RCA device was designed to operate in the X-band. The dimensions of the compact RCA device are 45×45×24 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%.