Strapped magnetron with a dielectric resonator for absorbing radiation

1. A strapped magnetron comprising an anode having a plurality of vanes defining a plurality of cavities and a dielectric resonator in communication with the plurality of vanes, the dielectric resonator being arrange to at least partially absorb radiation generated in a predetermined mode of operation of the magnetron.

2. A strapped magnetron as claimed in claim 1 , in which each of the vanes are disposed about a common axis, the dielectric resonator is annular and is substantially coaxial with each of the vanes.

3. A strapped magnetron as claimed in claim 1 , wherein the dielectric resonator has dimensions which are such that a predetermined resonance between each of the vanes and a pole piece of the magnetron is substantially equal to a frequency of the predetermined mode of operation.

4. A strapped magnetron as claimed in claim 1 , in which the predetermined mode of operation is the pi−1 mode.

5. A strapped magnetron as claimed in claim 1 , in which the dielectric resonator is comprised of ceramic material.

6. A strapped magnetron as claimed in claim 5 , in which the ceramic material is alumina.

7. A strapped magnetron as claimed in claim 1 , in which the dielectric resonator comprises a first portion and a second portion and the first portion of the dielectric resonator is lossy.

8. A strapped magnetron as claimed in claim 7 , in which each of the vanes are disposed about a common axis and the resonator is substantially co-axial with each of the vanes.

9. A strapped magnetron as claimed in claim 7 , in which the predetermined mode of operation is the pi−1 mode.

10. A strapped magnetron as claimed in claim 7 , in which the first portion of the dielectric resonator comprises a first annular member and the second portion comprises a second annular member, the first and second annular members being substantially coaxial.

11. A strapped magnetron as claimed in claim 10 , further comprising a third member of electrically conductive material sandwiched between the first and second annular members.

12. A strapped magnetron as claimed in claim 11 , in which the third member is annular and substantially coaxial with the first and second members.

13. A strapped magnetron as claimed in claim 7 , in which the dielectric resonator includes ceramic material.

14. A strapped magnetron as claimed in claim 13 , in which the ceramic material is alumina.

15. A strapped magnetron as claimed in claim 13 , in which the first lossy portion which is lossy comprises ceramic material loaded with carbon.

16. A strapped magnetron as claimed in claim 7 , in which the first lossy portion of the resonator is located further from the anode vane than the second portion.

17. A strapped magnetron as claimed in claim 7 , in which the first lossy portion of the resonator is thinner than the second portion.

18. A strapped magnetron as claimed in claim 17 , in which the first lossy portion of the resonator has a thickness less than one quarter of that of the second portion.

19. A strapped magnetron as claimed in claim 7 , further comprising an electrically conductive region interposed between the first portion and the second portion.

20. A strapped magnetron comprising an anode having a plurality of vanes defining a plurality of cavities and a dielectric resonator in communication with the plurality of vanes, the dielectric resonator being arranged to at least partially absorb radiation generated in a predetermined mode of operation of the magnetron in which the dielectric resonator comprises a first portion and a second portion and the first portion of the dielectric resonator is lossy and an electrically conductive region interposed between the first portion and the second portion.

21. A strapped magnetron comprising an anode having a plurality of vanes defining a plurality of cavities and a dielectric resonator in communication with at least one of the vanes the dielectric resonator being arranged, in use, to at least partially absorb radiation generated in a predetermined mode of operation of the magnetron.

22. A strapped magnetron as claimed in claim 21 , in which a portion of the dielectric resonator is lossy.