To provide a filter and a duplexer wherein conductive regions are sufficiently separated from each other and dimension accuracy of filter patterns and input/output pads is improved.
A duplexer 42 is constituted of a dielectric block that is a polygon including at least one flat outer surface. Furthermore, the entire outer surface of a polygon of the dielectric block is coated with a metallic material. A ground plane 80 is formed as a metal surface constituted of a conductive material 82. A reception filter 46 is formed in a first area on the flat surface of the dielectric block 1 and includes conductive elements 60, 62, 64, 66, 68. The first conductive element is surrounded with trenches or recesses 74, 76, 78 so that the conductive elements are electrically isolated from each other, each of the conductive elements is recessed just for predetermined depth or width, thereby inducing electrostatic coupling between the conductive element and the ground plane, and operational characteristics of the reception filter such as an operational frequency can be adjusted by the electrostatic coupling.
ROMBACH EDWARD J
SIMONS RANDAL N
PASCO WAYNE D
