High frequency filter

Abstract

A high frequency filter incorporates: an unbalanced input/output terminal; two balanced input/output terminals; two resonators respectively provided between the unbalanced input/output terminal and the two balanced input/output terminals; and a layered substrate for integrating components of the high frequency filter. The two resonators are inductively coupled to each other, and are also capacitively coupled to each other through two capacitors. Each of the two capacitors is formed using a pair of first and second electrodes and a dielectric layer. The first electrode is connected to one of the resonators via a through hole. The second electrode is connected to the other of the resonators and opposed to the first electrode forming the pair with the second electrode, the dielectric layer being disposed between the second electrode and the first electrode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating the circuit configuration of a high frequency filter of a first embodiment of the invention.

FIG. 2 is a perspective view illustrating an appearance of the high frequency filter of the first embodiment of the invention.

FIG. 3 is a top view of the top surface of a first dielectric layer of the layered substrate of FIG. 2.

FIG. 4 is a top view of the top surface of a second dielectric layer of the layered substrate of FIG. 2.

FIG. 5 is a top view of the top surface of a third dielectric layer of the layered substrate of FIG. 2.

FIG. 6 is a top view of the top surface of a fourth dielectric layer of the layered substrate of FIG. 2.

FIG. 7 is a top view of the top surface of a fifth dielectric layer of the layered substrate of FIG. 2.

FIG. 8 is a top view of the top surface of a sixth dielectric layer of the layered substrate of FIG. 2.

FIG. 9 is a top view of the top surface of a seventh dielectric layer of the layered substrate of FIG. 2.

FIG. 10 is a top view of the top surface of an eighth dielectric layer of the layered substrate of FIG. 2.

FIG. 11 is a top view of the top surface of a ninth dielectric layer of the layered substrate of FIG. 2.

FIG. 12 is a top view of the top surface of a tenth dielectric layer of the layered substrate of FIG. 2.

FIG. 13 is a top view illustrating the tenth dielectric layer and a conductor layer therebelow of the layered substrate of FIG. 2.

FIG. 14 is a top view of the top surface of a third dielectric layer of a layered substrate of a high frequency filter of a second embodiment of the invention.

FIG. 15 is a top view of the top surface of a fourth dielectric layer of the layered substrate of the high frequency filter of the second embodiment of the invention.

FIG. 16 is a top view of the top surface of a third dielectric layer of a layered substrate of a high frequency filter of a third embodiment of the invention.

FIG. 17 is a top view of the top surface of a fourth dielectric layer of the layered substrate of the high frequency filter of the third embodiment of the invention.

FIG. 18 is a top view of the top surface of a third dielectric layer of a layered substrate of a high frequency filter of a fourth embodiment of the invention.

FIG. 19 is a top view of the top surface of a fourth dielectric layer of the layered substrate of the high frequency filter of the fourth embodiment of the invention.

Claims

1. A high frequency filter comprising: a layered substrate including dielectric layers and conductor layers that are alternately stacked;a first resonator and a second resonator that are formed of part of the conductor layers inside the layered substrate and that are inductively coupled to each other;at least one pair of first and second electrodes that are formed of part of the conductor layers inside the layered substrate and that capacitively couple the first and second resonators to each other; andat least one through hole provided inside the layered substrate and connecting the first electrode to one of the first and second resonators, whereinthe second electrode is connected to the other one of the first and second resonators and opposed to the first electrode pairing up with the second electrode, one of the dielectric layers inside the layered substrate being disposed between the second electrode and the first electrode.

2. The high frequency filter according to claim 1, wherein the first and second resonators are disposed on an identical one of the dielectric layers inside the layered substrate.

3. The high frequency filter according to claim 1, wherein: each of the first and second resonators is a half-wave resonator with open ends;two pairs of the first and second electrodes are provided; andone of the two pairs of the first and second electrodes couple one of the ends of the first resonator to one of the ends of the second resonator, while the other of the two pairs of the first and second electrodes couple the other of the ends of the first resonator to the other of the ends of the second resonator.

4. The high frequency filter according to claim 3, further comprising an unbalanced input/output terminal for receiving or outputting unbalanced signals, and two balanced input/output terminals for receiving or outputting balanced signals, wherein the first and second resonators are provided between the unbalanced input/output terminal and the balanced input/output terminals for the sake of circuit configuration.