The development of low-noise pulse traveling wave tube amplifier for radar scatterometer

The traditional pulse traveling wave tube amplifier has been faced with some technical problems, such as high noise power spectral density, poor internal clutter index and low re-frequency gate modulation stability, which seriously restricted its application in the direction of radar scatterometer. A new type of low-noise pulse Traveling Wave Tube Amplifier (TWTA) is developed. The power supply firstly uses active filter controlled by pulse width modulation (PWM) technology to reduce the pulse current fluctuation of satellite bus. Secondly, a linear voltage regulator based on proportional integral differential (PID) regulation is used at the back stage of boost circuit to further reduce the ripple noise of cathode. The modulator circuit uses the multi-stage suspension isolation technology and frequency spreading circuit to increase the modulator gating stability and realize the function of low repetition pulse width modulation. Based on the above designed low-noise pulse traveling wave tube amplifier integrated with the power supply and TWT, the technical indexes that the noise power spectral density of the amplifier is lower than -110dBm /Hz and the clutter rejection of the product is lower than -75dBc are realized. It is applied to flight verification of a scattering scoring system to achieve the target that the wind speed measurement is better than 1.5m/s.