LTCC-Based Millimeter-Wave Wideband Scalable ±45° Dual-Polarized Antenna Array

This communication introduces a millimeter-wave (mmW) wideband scalable ±45° dual-polarized antenna array (DPAA) based on low-temperature cofired ceramic (LTCC) technology. The patch antennas, serving as dual-polarized elements, are rotated 45° to generate a low-sidelobe radiation patterns in E- and H-planes for both polarizations. A rectangular slot and a pair of Z-shaped probes are used to excite each patch element to generate ±45° dual-polarized radiation in a wideband. The rotation of radiating elements also creates adequate space for integrating differential feeding networks (FNs) within the footprint of the radiating part. This configuration enables the proposed DPAA to achieve the features of wideband dual-polarized radiation performance and array scalability simultaneously. Two separate differential FNs are embedded in multiple substrate layers to reduce the occupied space. They integrate cascaded wideband in-phase and out-of-phase power dividers (PDs), implemented by substrate-integrated waveguide (SIW) and substrate-integrated coaxial line (SICL) technologies, respectively. A prototype of a 4×4-element wideband ±45° DPAA is fabricated for demonstration. Experimental results show that the proposed DPAA exhibits stable radiation patterns with low sidelobe levels (SLLs) for both polarizations across the frequency range of 24.5-32.5 GHz (fractional bandwidth: 28%). In the same frequency range, the measured cross-polarization discrimination (XPD) is better than 38.2 dB and peak gain surpasses 16.5 dBi.