Enhancement of Phase Linearity in an FWG TWT by Utilizing Positive Phase Jumping Method

The increasing demand for communication quality has prompted the exploration of improving the linearity of folded waveguide (FWG) traveling wave tube (TWT). In this article, a positive phase jumping method (PPJM) is proposed to optimize the phase nonlinearity characteristic of FWG TWT. A particular structure based on this method is incorporated into the slow wave structure (SWS), which serves as the phase shifter. By changing the propagation state of the wave, it can cause a phase difference between the electron beam and the wave. Consequently, the time that the bunched electrons spend in the linear region is extended. For demonstration, the proposed method is applied in an E-band FWG TWT. Compared with the conventional one, the results demonstrated that the PPJM effectively enhances the phase linearity of the device as its output is retained. The values of amplitude modulation/phase modulation (AM/PM) conversion in the working band are reduced within 5.22°/dB–5.85°/dB from 7.4°/dB to 10.4°/dB, indicating a significant improvement of 29.5%–44.1%. Nonlinear phase shifts within the working band remain below 60°, while they fluctuate between 55° and 80° before optimization. The PPJM is simple, operable, and requires few extra modifications to conventional SWS, which enables it to have a promising prospect in the design optimization and engineering application of FWG TWT.