Predistortion Linearization of an X-Band TWTA for Communications Applications

Using a predistortion linearizer is an important way to improve traveling-wave tube amplifier (TWTA) linearity. However, predistortion linearizers cannot usually control amplitude modulation (AM)/AM and AM/phase modulation (PM) conversion separately, so it is difficult to satisfy linearization requirements for AM/AM and AM/PM conversion simultaneously. This paper proposes a predistortion linearizer with a relatively simple circuit structure, which provides good control of gain expansion over the input power dynamic range while keeping the amount of phase expansion small. Good linearity improvement has been obtained for a 45-W X-band TWTA with this predistortion linearizer.