Low Cross-Polarization SIW Slots Array Antenna With a Compact Feeding Network

A low cross-polarization-slotted substrate-integrated waveguide (SIW) cavity planar array antenna, which consists of four symmetrically arranged linear arrays, is presented in this letter. The linear array is fed through a coaxial probe located at the center of the SIW cavity, which ensures that two quasi-TE150 modes with approximate frequencies can be excited simultaneously. Therefore, the impedance bandwidth can be significantly improved by merging the two resonant frequencies. When the adjacent linear arrays are fed by reversed phase signals with uniform amplitude, extremely low cross polarization can be achieved in both E- and H- planes. The alternative reversed phase signals with uniform amplitude are simply generated by a compact SIW TE410 mode cavity. Measured results show that the proposed 4 × 4 planar array antenna achieves an impedance bandwidth ranging from 9.9 to 10.34 GHz. Within the operating band, the gain varies from 12.5 to 14.9 dBi. In E and H planes, the cross-polarization level is lower than -52.1 dB within the half-power beamwidth, and the sidelobe levels are below -13.4 and -18.4 dB, respectively. The aperture efficiency is up to 51.5%.