Wide Range of Harmonics Suppression of a Semicircular Patch Antenna Using Shorting Vias

In this letter, an effective approach is adopted to design a semicircular patch antenna at 5.8 GHz with a wide range of harmonics suppression. Initially, a circular patch antenna was designed with microstrip-coupled line feeding. The dominant mode TM110 is exciting at 5.8 GHz along with higher order modes TM210, TM010, and TM310 at 9.7 GHz, 11.9 GHz, and 13.5 GHz, respectively. The analysis is done up to 16 GHz due to measurement limitations. A perfect electric wall is created using plated through-hole vias along the central plane of the circular patch. The electric wall reduces the size to semicircular and suppresses higher order modes TM210 and TM010 without disturbing the modes TM110 and TM310 at 5.8 GHz and 13.5 GHz, respectively. To further suppress the higher order mode TM310, the conducting vias are shifted strategically to the electric field maxima position of this mode. In this way, size reduction and a wide range of harmonic suppression are achieved simultaneously. A prototype is fabricated and tested to verify the design. The measured and simulated results are in good agreement. The gain pattern is like filtering response, and its maximum value at the operating frequency is 5 dBi. The design exhibits a low profile (0.015λ0) and a compact overall size of 0.58λ0×0.48λ0.