GB1233030A - - Google Patents

Abstract

1,233,030. Microwave heating. VARIAN ASSOCIATES. 11 Oct., 1968 [13 Oct., 1967], No. 48440/68. Heading H5H. In order to ensure coupling to three subsets of resonator modes, a microwave heater comprises a multimode cavity resonator 12; a first coupling hole 51 adjacent a corner 67 of boundary wall of the cavity; a second coupling hole adjacent a corner 56 of a boundary wall, the proximate edge of each coupling hole being not further than #/2#2 from the adjacent corner, where # is the free space wavelength of microwave energy at a selected frequency with which the resonator is intended to be energized; first and second waveguides 53, 54 terminating at said respective coupling holes 51, 52, said first waveguide 53 and coupling hole being arranged to deliver said microwave energy at said selected frequency in such a manner as to excite the cavity 12 in two of said resonator mode subsets, and said second waveguide 54 and coupling hole 52 being arranged so as to excite cacity 12 in at least said third resonator mode subset; and means, e.g. mode stirrers 88, for varying the frequencies at which the resonator mode patterns occur about the selected frequency. The coupling holes 51, 52 and waveguides 53, 54 may be arranged adjacent any of the corners of the cavity 12 in any wall provided that they are oriented so that the electric field propogated by the waveguides have components lying parallel to the wall currents characteristic of the resonator mode subsets with which they are intended to be coupled. As shown, both waveguides propogate TE waves, waveguide 53 having components of its electric field parallel to wall currents characteristic of the first and third resonator mode subsets and waveguide 54 having components parallel to the wall currents characteristic of the second and third resonator mode subsets. If TM waveguides are used, their orientation is not critical. In addition to the two coupling holes 51, 52, further coupling holes may be provided at various locations of the cavity. A single generator may supply the two waveguides 53, 54 by means of a T-type junction. In other respects the microwave heater is identical with that disclosed in copending application No. 48442/68.