A helix slow-wave structure (SWS) for a high efficiency Ku-band 140 W space TWT has been designed. Cold circuit parameters of helix SWS like propagation constant and on axis interaction impedance were determined using 3-D electromagnetic field simulators ANSOFT-HFSS and CST-MWS and validated with the experimental results. In-house developed large-signal code SUNRAY-1D was used to design the complete helix SWS in 2-section with sever and taper to achieve desired output power, gain, efficiency, and other linearity parameters such as phase shift, AM/PM factor, I/M components. Simulated RF performance of the Ku-band 140W helix TWT was validated with the experimental results. A close agreement between the simulated and experimental results has been found.
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