Planar Ultra-Wideband Antennas in Ku- and K-Band for Pattern or Polarization Diversity Applications

Two planar diversity antennas operating in Ku- (12.4-18 GHz) and K-band (18-26.5 GHz) are proposed for ultra-wideband (UWB) applications. Both of them consist of a monopole radiating element and two orthogonal feeding ports. Their ground planes are modified and optimized to improve the isolation as well as to control the radiation. The first one is a pattern diversity antenna with a disc monopole patch. The second one is a polarization diversity antenna based on a square patch which is able to provide both linear and circular polarizations. Different feeding approaches are adopted to obtain a broadband impedance matching. Two wideband couplers are designed to provide the required feeding circuit. Both the simulated and measured results are presented to verify the proposed idea. Good radiation efficiency and isolation between the two ports are achieved. Consistent diversity performance is observed across the whole UWB bandwidth which is demonstrated by their radiation patterns.