Experiment on TWT 3IM suppression using harmonic and IM3 injection

Abstract

In this paper, both second harmonic and third order inter-modulation signals are experimentally injected into a traveling wave tube (TWT) to carry out the research on the suppression of IM3 in a X-band TWT. The results shows that with proper phase and amplitude of injected 2f₂ and 2f₂ - f₁, a significant reduction in the upper IM3 (2f₂ - f₁) is observed. IM3 suppression of up to 30.67 dB is examined with 2f₂ injection when Df = f₁- f₂ = 5MHz, and 15.75 dB IM3 suppression is obtained with IM3 (2f₂ - f₁) injection.