A magnetron includes a decoupling plate located between the end hat of the magnetron cathode and an output coupling member. The use of the decoupling plate presents a high impedance and gives a resonant circuit which is arranged to be resonant at the operating frequency of the magnetron. This prevents or reduces power loss due to capacitive coupling. In another arrangement, the decoupling plate is mounted to a post on the end hat of the magnetron cathode.
1. A magnetron, comprising:
a) a cathode coaxially surrounded by an anode;
b) an axial output having an output coupling member connected to the anode; and
c) a decoupling plate located between an end of the cathode and the member, the plate having dimensions and being located such that a resonant frequency of its equivalent circuit is substantially an operating frequency of the magnetron.
2. The magnetron as claimed in claim 1 , wherein the decoupling plate is a planar disc.
3. The magnetron as claimed in claim 1 , wherein the decoupling plate is supported by a post.
4. The magnetron as claimed in claim 3 , wherein the post is mounted on the cathode.
5. The magnetron as claimed in claim 1 , wherein the plate is constituted of copper.
6. The magnetron as claimed in claim 1 , wherein the anode includes a plurality of anode vanes, and wherein the member includes a disc and electrical connections to connect the disc with alternate ones of the anode vanes.
7. The magnetron as claimed in claim 3 , wherein the post is mounted on the member.
8. The magnetron as claimed in claim 1 , the magnetron being operative at X band.