A duplex filter includes a block of dielectric material with top, bottom, and side surfaces and first and second spaced-apart sets of through-holes. A pair of outside walls and a center wall extend outwardly from the top surface. A pattern of metallized areas is defined on the top surface of the block including first and second electrodes that extend on the pair of outside walls respectively and third and fourth electrode antennae that extend on the center wall. The block may be two separate blocks coupled together to form an interior layer of metallization separating the first and second sets of through-holes and the center wall separates respective transmit and receive portions of the pattern of metallized areas.