K-/Ka-Band Dual-Polarized Differential Series-Fed Waveguide Slot Array Antenna With Enhanced Boresight Radiation Bandwidth

This communication presents a hollow-waveguide (HW) differential series-fed continuous transverse stub (CTS)-based dual-band dual-polarized antenna (DBDPA) with wideband boresight radiation characteristics. The realization of the dual-band dual-polarized performance is based on the orthogonal layout of series-fed dual-band CTS elements. To ensure the boresight radiation of both polarizations at the center frequencies of two target bands, a 2-D slow wave structure (SWS) is loaded in the parallel-plate waveguide (PPW) to flexibly modulate the guided wavelengths to match the physical periods of CTS elements. By further employing two sets of orthogonal differential feeding networks, the frequency-induced squint beams can be superposed to form a boresight main beam in a wideband. Combined with the optimization of the physical period, the boresight radiation bandwidth with stable patterns in both bands has been improved. A prototype is fabricated and demonstrated. The measured results indicate that the boresight radiation bandwidth for both polarizations is extended to 17.5–20 GHz (K-band) and 28.5–30 GHz (Ka-band), respectively. In these two frequency ranges, the antenna efficiencies are both larger than 85%.