Miniaturized Dual-Band Filter Using Single Quad-Mode Monoblock Dielectric Resonator

A miniaturized dual-band filter using quad-mode monoblock dielectric resonator (MDR) is proposed in this letter. By designing the blind holes symmetrically and making full use of the perfect even and odd boundaries, the quad-mode M<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ee</sub>, M<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eo</sub>, M<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oe</sub>, and M<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oo</sub> exist simultaneously in the single ceramic. The feeding posts are inserted centrosymmetrically to obtain the transmission zero (TZ) between the quad-mode to get the dual-band performance. More importantly, in such a simple structure, the frequency of the quad mode can be manipulated, respectively, which makes the lower and upper passbands independently controlled with each other. For demonstration, the dual-band filter is designed, and the passbands are centered at 3.16 and 3.76 GHz, respectively. It features a lower insertion loss and more compact size compared with the published filters.