35 GHz widebandTE01-HE11 mode converter for Gyroklystron 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, 33-35GHz. High power transmitters, on the order of several hundred kilowatts will thus be required in the millimeter band. The only sources presently capable of producing this power level are Gyro devices, such as Gyroklystron, Gryo-TWT and Gyrotron. 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 TEoη 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 TEoη mode into a Gaussian beam is achieved through the use of several mode converters. One possible system of mode converters is depicted in Figure 1. Here the TEoi mode is emitted by the Gyroklystron into highly overmoded circular waveguide. The TEoi mode then enters the TEoi-TMn mode converter, which consists of circular waveguide sinusoidal bend. The TMn mode then enters a corrugated TMn -HEn mode converter, and finally exits into space through a corrugated horn section.