Waveguide bandstop filter

Claim 2

For a microwave oven having means defining an oven cooking cavity, a source of microwave energy at a predetermined frequency and a waveguide for coupling the energy from the source to the cavity, a filter for suppressing a harmonic of the operating microwave frequency comprising a resonant ring and means for supporting the resonant ring within the waveguide and from a wall thereof adjacent the source of microwave energy and having at least a part of the ring extending in the direction of the E vector of the field in the waveguide, said source including a magnetron having a radiating end with said ring disposed an emperically predetermined distance from the radiating end so as to minimize the magnitude of the second harmonic generated by the magnetron.

Claim 3

The filter of claim 1 wherein said means for supporting includes a conductive member having means for permitting its support from a narrow wall of the waveguide.

Claim 4

The filter of claim 2 wherein said ring is circular and has an inner diameter on the order of one wavelength of the center rejection band frequency.

Claim 5

The filter of claim 3 wherein said conductive member has a cross-sectional area equal to or greater than the width of the ring so as to provide good heat transfer.

Claim 6

The filter of claim 2 wherein said ring is rotatable to vary E vector coupling.

Claim 7

The filter of claim 1 wherein said means for supporting includes a dielectric member supporting said ring from a wide wall of the waveguide.

Claim 8

In combination: a plurality of walls defining an oven cooking cavity, a source of microwave energy for generating a signal having a principle operating frequency. a rectangular waveguide having a pair of broad walls and a pair of narrow walls and for coupling the signal from the source to the cooking cavity, a circular resonant ring filter structure for suppressing a harmonic of the operating microwave frequency, and means for supporting the resonant ring within the waveguide adjacent the source of microwave energy and having at least a part of the ring extending in the direction of the E vector of the field in the waveguide, said means for supporting the resonant ring including a conductive member having means for permitting its support from one of the narrow walls of the waveguide in a manner to allow limited rotation of the member which in turn rotates said ring to vary the suppression bandwidth without materially varying the center suppression frequency, said conductive member having a cross-sectional area equal to or greater than the width of the ring so as to provide good heat transfer between the ring and waveguide walls, and wherein said ring has an inner diameter on the order of one wavelength of the center rejection band frequency.

Claim 9

In combination: a plurality of walls defining an oven cooking cavity, a source of microwave energy for generating a signal having a principle operating frequency. a rectangular waveguide having a pair of broad walls and a pair of narrow walls and for coupling the signal from the source to the cooking cavity, a circular resonant ring filter structure for suppressing a harmonic of the operating microwave frequency, and means for supporting the resonant ring within the waveguide adjacent the source of microwave energy and having at least a part of the ring extending in the direction of the E vector of the field in the waveguide, said means for supporting the resonant ring including a conductive member having means for permitting its support from one of the narrow walls of the waveguide in a manner to allow limited rotation of the member which in turn rotates said ring to vary the suppression bandwidth without materially varying the center suppression frequency, said conductive member having a cross-sectional area equal to or greater than the width of the ring so as to provide good heat transfer between the ring and waveguide walls, and wherein said ring has an inner diameter on the order of one wavelength of the center rejection band frequency.