Intrapulse noise in radar TWT amplifiers

In coherent radars, the transmitted pulse must be free of any undesirable instabilities introduced in the transmission chain. Therefore, it is important to know the effect of radar sensitivity on the stability requirements which the transmitter high-voltage power supplies have to meet. The ripple on the TWT power supply voltages determines the RF signal phase variations, and, consequently, there are additional modulation lines in the transmitted pulse distribution. The modulation process is analyzed mathematically, and results are presented of intrapulse noise measurements carried out on a radar transmitter using switched-mode power supplies synchronized with the radar PRFs. The benefits afforded by improvements to power supply stability are discussed.