Design and Experimental Demonstration of a Low-Profile Differential-Fed Tri-Band Filtering Antenna

The design and validation of a novel low-profile, differential-fed tri-band filtering antenna are demonstrated. The design consists of a driven patch and two pairs of parasitic strips. Four commensal stubs are added to the driven patch to improve the rate of attenuation at the band edge of the second working frequency band. Additionally, split-ring slots and shorted parasitic strips are appropriately incorporated to tailor the reflection coefficient and enhance the bandwidth of the corresponding working band. Overall, the antenna has a low profile of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.03λ₁</tex> and a small footprint, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.09λ_1²</tex> , where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ₁</tex> represents the wavelength associated with the central frequency of the first operating band. Measurements of its prototype confirmed the same polarization direction and similar radiation properties over the tri-band antenna's operating frequency ranges of 2.4-2.487 GHz, 3.72-3.93 GHz, and 5.57-5.88 GHz. Because the antenna is built in a single-layer configuration, it and its operating bands can be easily scaled up to millimeter wave and even terahertz frequencies for related applications.