Thales extends its offer of high power TWT's for satellite uplink applications with the TH4092 , a 500 W peak / 350 W CW TWT in the 27.5-30 & 30-31 GHz frequency ranges. The last phase of the development program was successfully completed. The prototype results show high efficiency and good linearity performances. Margin and qualification tests are nearly finished and the industrial means are in place to begin the production.Figure 1: Outline of TH4092 Design of 500W Ka band TWTTo ensure a high reliability, the TH4092 has been designed to sustain a 500W CW RF output power level to ensure margins in specified operating conditions. The design effort has been concentrated on the RF characteristics and on the thermal aspects of the new subassemblies. Duration and environmental tests performed on several prototypes, linked to simulations, have demonstrated that the maximum temperatures and stresses remain well below critical limits at the various operating points.The gun is equipped with a negative anode A0 (with respect to ground) which allows, in combination with the cathode voltage, to optimize the operating point and thus the electrical and RF characteristics (linearity, RF output power and gain). This electrode can also be used to regulate the cathode current over life. A positive ion barrier A1 protects the cathode and increases the lifetime.A new helix -rods system has been defined to increase beam efficiency and ensure a stable operation, free of oscillations. With the help of a four-stage collector, the overall efficiency is typically 55% at saturation and 45% for 350 W RF output power.

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