A Triple-Mode Wideband Filtering Antenna With Planar Configuration by Combining One SIW Cavity and Two Half-Mode Patch Resonators

In this letter, a triple-mode wideband filtering antenna with a planar configuration is presented. The designed antenna has a single substrate layer, which consists of one half-mode circular patch resonator, one half-mode rectangular patch resonator, and one rectangular substrate integrated waveguide (SIW) cavity, and it is fed through the conventional coaxial probe. On the basis of the field analysis, these three types of resonators are compactly integrated without disturbing the resonant properties of their dominant modes. Given this, three resonant modes of half-TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub>, half-TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub>, and TE<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> are well generated, so as to form a widened operating band. Meanwhile, four radiation nulls are produced from far-field radiation cancellation with the increased radiation boundaries. For validation, a prototype antenna with a center frequency of 2.8 GHz is designed and fabricated. The measured results indicate that the proposed antenna achieves an improved fractional bandwidth of 15.7% under three in-band resonances. Besides, four radiation nulls created at 2.32 GHz, 3.22 GHz, 3.49 GHz, and 3.89 GHz in stopband effectively enhance the out-of-band suppression level. Moreover, low profile of 0.037<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula> is also implemented.