Dual-Band Dual-Polarized Shared-Aperture Grid Antenna With Large Frequency Ratio

In this letter, a dual-band, dual-polarized, shared-aperture grid antenna with a large frequency ratio is presented. To achieve a shared aperture and large frequency ratio, a millimeter-wave (mm-Wave) partially reflective surface (PRS) is embedded into a microwave patch antenna. A periodic circular grid patch is adopted not only as the microwave antenna but also as the mm-Wave PRS antenna. The mm-Wave PRS antenna is centrally excited by a cross-shaped waveguide with two coaxial connectors, and the microwave patch antenna is driven by a pair of orthogonal L-shaped probes, resulting in polarization diversity in both bands. A compact microstrip resonant cell and a metal post are designed to reduce the couplings between different ports. For demonstration, a prototype operating in the 3.5 and 28 GHz bands is fabricated and measured. The overlapped measured −10 dB impedance bandwidths between the orthogonal ports cover 3.41–3.59 GHz (5.14%) and 26.62–30.26 GHz (12.8%) in the low and high bands, whereas the measured peak realized gains of 8.75 and 12.79 dBi are obtained, respectively. All port-to-port isolations are larger than 20 dB over the bands of operation.