A Singly-Fed Dual-Band Aperture-Sharing SIW Cavity-Backed Slot Antenna With Large Frequency Ratio

A singly-fed dual-band aperture-sharing slot antenna with a large frequency ratio is investigated, based on the substrate integrated waveguide (SIW) technology. The dual-band antenna consists of a rectangular slotted SIW cavity operating at 40 GHz millimeter-wave (MMW) band and a ring slotted SIW cavity operating at 5.2 GHz microwave (MW) band. Due to the self-shielding effect of the SIW cavity, the two radiating elements can be tightly nested with each other, leading to a compact structure with a high ratio of radiating aperture utilization. The MW and MMW SIW radiating elements are fed via a common microstrip line through two separate slots, and they are excited in the hybrid TMh (120, 210) mode and TMh (230, 320) mode respectively. In order to avoid the signal crosstalk, a transverse stub of half-wavelength (in terms of MMW frequency) is added onto the microstrip feed line to prevent the MMW signal from getting into the MW element, while the MMW element can naturally reject the MW signal for its high-pass characteristics. Consequently, good radiation performance is obtained at both the MW and MMW bands, and moreover, the two bands can be independently adjusted.