A Filtering Dense Dielectric Patch Antenna with Permittivity-Graded Structures

This paper proposes a novel Filtering Dense Dielectric Patch Antenna (DDPA). The antenna include a dense dielectric patch (DDP) and a double-layer printed circuit board (PCB) structure. The proposed filtering DDPA exhibits three resonant modes, with the first two modes operating in TE <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${ }_{11}$</tex> mode and the third mode in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{TE}_{12}$</tex> mode. By encircling the cylindrical DDP with an annular DDP of higher permittivity, the introduction of a low-frequency radiation zero is proposed., whose position can be independently adjusted by modifying the thickness of the outer annular DDP. The radiation null at the higher frequency edge of the passband originates from the non-radiative <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{TE}_{12}$</tex> mode of the cylindrical DDP itself. To reduce the TE 12 mode, two cylindrical holes are drilled on both sides of the DDP structure and silverplated along their sidewalls. Simulation results demonstrate that the proposed filtering DDPA reaches a relative bandwidth of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{1 3. 7 \%}$</tex> (3.82 GHz to 4.38 GHz, spanning 0.56 GHz). The average gain was determined to be <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{6. 7 4} \mathbf{~ d B i}$</tex>.