Abstract: A microwave signal linearizer for a travelling wave tube amplifier (TWTA) provides for simple and flexible adjustment of a predistortion network suitable for independently compensating for a wide range of travelling wave tube amplifier-induced distortions. The linearizer or predistortion network is formed by three divided parallel passive microwave signal channels, the first channel having a coaxial microwave limiter diode network, the second channel having a variable attenuator for adjusting amplitude modulation (AM/AM) non-linearity, and a third channel for adjusting amplitude modulation to phase modulation (AM/PM) non-linearity. Signals directed to the first and second channels are combined in a 180.degree. hybrid network to produce a difference signal which is directed through a difference channel to a 90.degree. hybrid network. The signals through the third channel are directed to the 90.degree.