Patent ID: 6921889

Claim:
A magnetron, comprising: a ring-shaped anode forming a plurality of resonance circuits; a cathode disposed at an axial center of the anode to emit thermions, separated from the anode by a predetermined space; a ring-shaped permanent magnet provided above the anode; an upper pole piece having a magnetic flux dispersing structure to carry magnetic flux generated by the permanent magnet to an upper portion of the predetermined space, wherein the upper pole piece comprises: a ring-shaped magnetic flux receiving portion disposed between the permanent magnet and the anode to receive magnetic flux generated by the permanent magnet; a slanted portion downwardly slantingly extended from an inner edge of the ring-shaped magnetic flux receiving portion to an upper portion of the predetermined space to carry received magnetic flux to the upper portion of the predetermined space; and a magnetic flux dispersing portion upwardly slantingly extended from an upper edge of the slanted portion to disperse the carried magnetic flux; a lower pole piece carrying the magnetic flux to a lower portion of the predetermined space; and at least one yoke magnetically connecting the permanent magnet with the lower pole piece.