A 34.5 GHz 200 kW CW TM/sub 11/-HE/sub 11/ mode converter for gyrotron applications

Future plans call for increasing the uplink and downlink frequencies used for communication with deep space probes from the present 2 GHz and 8 GHz bands into the millimeter band, 32-35 GHz. High power transmitters, of the order of several hundred kilowatts CW will be required in the millimeter band. The only sources presently capable of producing this power level are gyro devices. In order to produce these power levels gyro devices employ unconventional interaction cavities. These cavities resonate in higher order waveguide modes, and typically deliver the output signal into an oversize circular waveguide in a higher order waveguide mode, such as a TE/sub 0N/ mode. If the power is to be used constructively, for example to illuminate a reflector antenna, a Gaussian beam is typically required. Transformation of the TE/sub 0N/ mode into a Gaussian beam is achieved through the use of several mode converters. One possible system of mode converters is depicted. The mode converters used to generate the TM/sub 11/ mode required for testing the TM/sub 11/-HE/sub 11/ mode converter are described.