Codesigned High-Efficiency Single-Layered Substrate Integrated Waveguide Filtering Antenna With a Controllable Radiation Null

This letter proposes a codesigned substrate integrated waveguide (SIW) filtering slot antenna with a controllable radiation null in gain response. The antenna is composed of a single-layered SIW cavity, four metalized posts, a transverse slot, and a vertical SMA connector. Four metalized posts are introduced to split the cavity into two TE 110-mode resonators. The transverse slot is utilized not only to generate radiation, but also to further split one TE110-mode resonator into two half-mode resonators. The bandpass filtering performance is achieved by the couplings between three resonators and the slot. One radiation null has been introduced for selectivity enhancement, and it will occur at the frequency where the slot is placed at about quarter-wavelength from the shorted wall of the cavity. So by changing the position of the slot, frequency of radiation null can be easily controlled, even from one side to another side of the passband. For demonstration, one antenna with a lower out-of-band radiation null and another one with an upper out-of-band radiation null have been designed, fabricated, and measured. Experimental results show that the antennas have the merits of high efficiency, high selectivity, and easily controllable radiation null.