Improved Gain Equalization Technique for Q-Band Folded-Waveguide TWT for Potential Application in High-Data-Rate Communication

With demanding applications in high-data-rate communication, a folded-waveguide (FWG) traveling-wave tube (TWT) faces the challenge of gain fluctuation and bandwidth limitation. To flatten gain and extend bandwidth, a novel 3-stage gain equalization technique (GET) is proposed and applied in FWG-TWT in this article. This technique shifts the operating point to a high-frequency range in the middle section. Gain equalization can be implemented by improving gain at high frequency and decreasing gain at low frequency. Furthermore, the GET also has a significant advantage in extending bandwidth. Accordingly, a 3-stage FWG-TWT is realized. Compared with a
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-band FWG-TWT with a uniform slow-wave structure (SWS), the 3-stage FWG-TWT extends the 3-dB bandwidth by more than ~45% and the gain variation less than 0.3 dB in the operating bandwidth, which demonstrates great improvement.