Feedforward and predistortion linearizers on an X-band helix-TWT

Abstract

Research on linearizing an X-band helix-TWT is performed. Both feedforward and predistortion linearizing circuits are designed and fabricated. Output frequency spectra are measured to compare the third order intermodulation distortion amplitudes of the TWT with linearization and without linearization. When a two-tone signal of 9.5 GHz and 9.505 GHz is injected with 6 dBm input power, the output power is measured to be 1.2 W and the third-order intermodulation distortion (IMD) is 45.6 dB. The third-order IMD is improved by 25.6 dB, compared with the TWT without the linearizing circuit.