A Single-Layer Filtering Antenna With Two Controllable Radiation Nulls Based on the Multimodes of Patch and SIW Resonators

A single-layer filtering hybrid antenna with low profile and high selectivity is presented. The proposed antenna is composed of a triangular patch and a substrate integrated waveguide (SIW) cavity with triangular slot and U-shaped slot etched on the top surface. The patch is embedded in the triangular slot. Four modes can be generated by the hybrid structure. That is, the TM ₁₀ mode of the patch, the right half-TE ₁₁ , the modified right half-TE ₁₁ and the TE _{1.5, 1} modes of the SIW cavity are selected. By merging the four modes into a single passband, the impedance bandwidth is broadened, and the frequency selectivity is enhanced. There are two radiation nulls at the lower and upper edges of the passband, which can be controlled independently. In addition, part of the shorting pins surrounding the SIW cavity is truncated to decrease the operating frequency and increase the out-of-band rejection. The measured –10 dB impedance bandwidth ranges from 3.44 to 3.62 GHz with sharp frequency selectivity and more than 18 dB out-of-band suppression level.