Study on the Effect of Digital Predistortion on Signal Quality of Travelling-wave Tube Transmitter

The linearization technology represented by digital predistortion is an important means to improve the quality of high-power transmitting signals. In this paper, a digital predistortion scheme is designed. An experimental verification is carried out on X band, 100 W TWT transmitter, and the improvement effect on the signal quality is achieved: error vector magnitude (EVM) falls from 8% to 5%; third-order intermodulation is reduced about 10 dB; the consistency of phase between channels is improved about 10° with different input power level; the -3 dB width of amplitude in time domain is improved by 1.33 microseconds. On this basis, the effect of digital predistortion technology on the improvement of transmitted signal quality is analyzed from the perspectives of time domain and frequency domain.