| CPC H01Q 5/307 (2015.01) [H01Q 9/16 (2013.01); H01Q 15/14 (2013.01)] | 5 Claims |

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1. A cavity filter comprising a plurality of resonator elements, wherein each resonator element comprises a plurality of stubs adjusted in frequency and arranged according to a geometric shape to be selected from an ellipse or a rectangle, wherein each resonator element is disposed on a layer of dielectric material and separated from each other by a layer of foam-type material or air, wherein the dielectric materials include a variable dielectric constant to change the working frequency or its phase response, to perform low-pass, high-pass, band-pass or multiband-pass filters.
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