Dielectric filter, dielectric duplexer, and communication device

A dielectric duplexer comprising:

• a pair of dielectric filters, one of said filters being a dielectric filter comprising:
• a substantially rectangular parallelepiped dielectric block;
• a plurality of inner-conductor holes extending from a top surface to an opposing bottom surface of the dielectric block;
• an inner conductor provided on the respective surface of each of the inner-conductor holes;
• an outer conductor formed on outer surfaces of the dielectric block;
• and
• I/O electrodes extending from side-surfaces to an undersurface of the dielectric block, the side-surfaces being orthogonal to a direction in which the inner-conductor holes are arrayed in the dielectric block, and the undersurface being a mounting surface for being mounted on a mounting board,
• wherein the I/O electrodes are separated from the outer conductor and provide capacitance between the I/O electrodes and the plurality of inner-conductor holes,
• at least one of the I/O electrodes extends onto the undersurface of the dielectric block so as to overlie at least two of the inner-conductor holes when viewed from the undersurface, and further extends from the corresponding side-surface to a point beyond the second one of the at least two inner-conductor holes in a direction away from the corresponding side-surface for providing the capacitance stability between the second one of the at least two inner-conductor holes and the at least one of the I/O electrodes;
• and
• wherein a first one and a second one of the at least two inner-conductor holes are capacitively coupled to each other.

A dielectric filter comprising:

• a substantially rectangular parallelepiped dielectric block;
• a plurality of inner-conductor holes extending from a top surface to an opposing bottom surface of the dielectric block;
• an inner conductor provided on the respective surface of each of the inner-conductor holes;
• an outer conductor formed on outer surfaces of the dielectric block;
• and
• I/O electrodes extending from side-surfaces to an undersurface of the dielectric block, the side-surfaces being orthogonal to a direction in which the inner-conductor holes are arrayed in the dielectric block, and the undersurface being a mounting surface for being mounted on a mounting board,
• wherein the I/O electrodes are separated from the outer conductor and provide capacitance between the I/O electrodes and the plurality of inner-conductor holes,
• at least one of the I/O electrodes is disposed in such a position on the undersurface of the dielectric block as to couple to at least two of the inner-conductor holes, and extends from the corresponding side-surface to a point beyond the second one of the at least two inner-conductor holes in a direction away from the corresponding side-surface for providing the capacitance stability between the second one of the at least two inner-conductor holes and the at least one of the I/O electrodes;
• and
• wherein a first one and a second one of the at least two inner-conductor holes are capacitively coupled to each other.