Development Of Middle Power X-Band TWT Transmitter

With development of the art of military radar, it is required better parameters such as power out, phase stability, bandwidth, efficiency, reliability, volume, weight and so on. At present, travelling wave tube amplifier (TWTA) has particular advantages in these areas. In order to achieve specifications of transmitter which is required by the designer of a fire finder radar system in our institute, the author has researched and developed an X-band grid-controlled TWTA.The grid-controlled TWTA consists mostly of microwave power amplifying chain, transmitter control system, pulse modulator and high voltage (HV) power supply, and their functions and compositions are illustrated in this paper. The author analyzes some factors which affect the power gain and phase modulated noise in TWTA. To get these required specifications of TWTA, the author has studied some theory and computed some parameters. Finally, the way to design an X-band grid-controlled TWTA is obtained and the prototype is developed. Microwave power amplifying chain consisting of a solid state amplifier module and two-stage depressed-voltage TWT, thick film float deck modulator with high reliability, HV power supply based on full-bridge soft switching technology, heater and bias power supply with isolating voltage stabilization technology, control circuit with FPGA hardware were used in this TWTA. HV, heater and bias power supply were encapsulated in epoxy polymer. As a result, the weight and volume of power supply was reduced.At present, the transmitter has been successfully developed and used in the fire-finder radar system. In the process that the transmitter was used, it is stable and reliable.