Dielectric duplexer with different capacitive coupling between antenna pad and transmitting and receiving sections

A dielectric duplexer comprising:

• a dielectric ceramic block;
• a plurality of juxtaposed resonators provided in the dielectric ceramic block, which include through holes extended through the dielectric ceramic block sequentially along a direction and internal conductors covering the inner peripheral surfaces of the through holes, the resonators being divided into a group of resonators located near a lateral side of the dielectric ceramic block and operating as a transmitting section and another group of resonators located near the opposite lateral side of the dielectric ceramic block and operating as a receiving section;
• an external conductor covering the outer peripheral surface of the dielectric ceramic block except the open-circuit end surface on which one end of each through hole is exposed;
• a first input/output pad arranged on the dielectric ceramic block and electrically isolated from the external conductor but capacitively coupled to the outermost resonator of the transmitting section;
• a second input/output pad arranged on the dielectric ceramic block and electrically isolated from the external conductor but capacitively coupled to the outermost resonator of the receiving section;
• and
• an antenna terminal pad arranged only on a side surface of the dielectric ceramic block, electrically isolated from the external conductor, and capacitively coupled through the block to the innermost resonator of the transmitting section and the innermost resonator of the receiving section located adjacent to the innermost resonator of the transmitting section, respectively, the antenna terminal pad, the innermost resonator of the transmitting section and the innermost resonator of the receiving section being relatively positioned to each other, and the capacitive coupling between the antenna terminal pad and the innermost resonator of the transmitting section being of greater value than the capacitive coupling between the antenna terminal pad and the innermost resonator of the receiving section.