An S/Ka-band shared-aperture antenna array with grating lobe suppression in millimeter-wave band

A dual frequency shared-aperture antenna array with grating lobe suppression in millimeter wave (mmW) band is investigated in this letter. It consists of a patch antenna working at 2.34 GHz with the fundamental TM10 mode and a slotted substrate integrated waveguide (SIW) cavity-backed antenna array working at 28.5 GHz with the element excited in TE440 cavity mode. The ground of mmW slot array antenna is employed as the radiation patch in microwave band, so high aperture reuse efficiency can be realized. By using a staggered distribution technique, the serious grating lobe of the high-order mode SIW antenna array with large element spacing can be greatly suppressed. A prototype is fabricated and the measurement grating lobe levels are lower than -18.5 dB at 28.5 GHz. The ratio of two antennas operating frequency reaches 12.1:1. The measured channel isolation between the two parts reaches -45 dB at 2.35 GHz and 35 dB at 28.5 GHz, respectively.