Abstract: The modern satellite communication uses non-constant envelope digital modulation techniques and thus demands for the high efficiency, wideband linear high-power amplifiers. The travelling wave tube (TWT) amplifier is widely used in digital wireless communication systems because of its high power efficiency and broadband, but its strong nonlinear characteristic generates intermodulation distortion, which degrades the data quality of transmitted signal and causes interference in adjacent channels. The current techniques such as baseband prediction and feedforward technique cannot achieve wideband greater than 1 GHz, and they are too complex to be used on satellite. This paper presents a broadband predistortion TWT linearizer. A frequency bandwidth of 1.2 GHz has been demonstrated with a K-band TWTA between 19.8 GHz and 21.0 GHz. The measurement result shows that the linearizer delivers about 2 dB to 5 dB of gain expansion and 20-50 degrees phase shift expansion. And the cascaded LTWTA shows good nonlinearity improvement of 17.8 dB at 6 dB input power back off point.