Patent ID: 7567141

Claim:
A nonreciprocal circuit device comprising: permanent magnets; a ferrite core to which a direct-current magnetic field is applied from the permanent magnets; a plurality of center electrodes disposed on the ferrite core; a circuit substrate; and a magnetic yoke; wherein the plurality of center electrodes are disposed on main surfaces of the ferrite core so as to intersect with one another and are electrically insulated from one another; the ferrite core and the permanent magnets are disposed substantially in parallel so that main surfaces thereof face each other and are substantially perpendicular to a surface of the circuit substrate; the magnetic yoke has a ring-like shape so as to surround the ferrite core and the permanent magnets with surfaces thereof substantially perpendicular to the surface of the circuit substrate; a shield conductor made of a nonmagnetic metal conductive material is disposed directly above the ferrite core and the permanent magnets to cover an opening portion of the magnetic yoke; and the shield conductor includes an opening area at a position facing at least one of shorter sides of the ferrite core.