A TWT power supply for high phase stability transmitter

The author describes the design of a TWT (traveling wave tube) power supply for use in a radar transmitter where phase stability of the RF output is the primary requirement. The transmitter has a peak power output of 155 kW at 2% duty cycle. In order to meet the phase stability requirements, the pulse-to-pulse ripple on the TWT cathode-to-body (25 kV to ground) and cathode-to-collector (15 kV) voltage supplies must be kept below 3 V_PP and 80 V_PP respectively. Ripple is produced by the switching frequency of the power supply, by variations in the main power supply line voltage and by changes in the radar PRF (stagger). The author describes the switching circuits and the techniques used to minimize ripple on the above supply voltages