To provide a ceramic duplex filter that facilitates tuning and manufacturing processes and improves reliability.
The ceramic duplex filter (10) has a filter body (12) of a dielectric material, and has a top (14), bottom and side surfaces (18, 20, 22, and 24) with through-holes extending from the top (14) to the bottom surface. Receptacles are positioned adjacent to the top surface (14) with a conductive material therein. The surfaces (16, 18, 20, 22 and 24) are substantially covered with a conductive material defining a metallized layer (25), with the exception that the top surface (14) is substantially unmetallized. The receptacles include a conductive layer of material to define a certain capacitance. Coupling devices (94, 96 and 98) for coupling signals into and out of the duplex filter (10) are provided. Shunt, series and coupling capacitors are strategically positioned adjacent to the top surface (14), which help to facilitate tuning of the filter.
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