Magnetron filter box

Claim 1

A combination of a magnetron and magnetron filter box comprising: a magnetron which includes a body portion, said body portion having an elongated stemlike end, and said stemlike end containing cathode and filament terminals, a pole piece of ferrous material, said pole piece containing an opening therethrough, said body portion positioned with said stemlike end extending through said opening and projecting outward from the surface of said pole piece, and means preventing microwave energy leakage through said pole piece opening between said body portion and said pole piece; first and second elongated electrical conductor means for carrying electrical filament current and a high cathode electrical voltage, said electrical conductor means being insulated electrically from one another and having first respective end portions adjacent one another and each connected to a respective one of the cathode and filament terminals of said microwave tube; microwave dissipative material for dissipating microwave energy and comprising a predetermined volume, Vl, said microwave dissipative material surrounding said first and second conductor means and extending therealong a major portion of the length thereof each to a point proximate said end portions of said conductor means; microwave cavity means defining a predetermined region of volume Vc for confining microwave energy therewithin, said cavity comprising walls of electrically conductive material and including as one wall thereof a portion of said pole piece surface, said microwave cavity including therein said electrical conductor means, said stemlike ends of said magnetron body and said microwave dissipative material; means for providing a filament current and high voltage path to said conductor means from outside said cavity; and wherein the volume of said cavity, Vc, and the volume of said dissipative material, Vl, define a ratio of Vc to Vl, which ratio comprises a quantity equal to or less than 20 whereby said microwave cavity is of a low Q factor electrical characteristic; and wherein a predetermined impedance Zo is defined as approximately equal to 377 (S divided by P) ohms, wherein said relationship of S and P being such that said Zo is equal to or less than 50 ohms, where S is defined as an average spacing distance between the outer surface of said dissipative material and the inner wall surfaces of said cavity means and where P is defined as a mean perimeter length about the space between said dissipative material and said cavity walls.