Substrate-Integrated Millimeter-Wave Short Backfire Antenna Excited by a Novel Quad-Slot Cavity-Back Feed

This paper describes a millimeter-wave (mm-wave) short backfire antenna (SBA), which can be fully integrated in a multilayer Printed Circuit Board structure and is very easy to be codesigned with other planar circuits. In our proposed design, a cavity with a depth of about half a wavelength is etched in the multilayer substrate. The primary reflector and subreflector are separately printed on substrate layers above and below the cavity. Metallized vias are used to obtain a rim on the primary reflector. The antenna is excited by a novel cavity-backed quad-slot feed, which performs a lower cross-polarization level than conventional single- or dual-slot cavity-backed feed. A prototype is fabricated at Ka-band with a center frequency of 31.75 GHz for demonstration. Investigations show that the antenna can present a bandwidth of ~250 MHz and peak gain higher than 15.5 dBi at its center frequency. A cross-polarization level better than -30 dB is also obtained in our measurement. The proposed substrate-integrated SBA is the first to be reported and very suitable to be involved in mm-wave system-in-package designs with other components.