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Backward wave oscillation suppression study of the helix travelling wave tube
摘要： In this paper, the effect of backward wave oscillation (BWO) on helix slow wave structure performance for TWT has been described. In this paper both the cases tapered and untapered helix slow wave structure (SWS) have been analyzed, caused by BWO for high gain helix TWT. In house developed the one-dimensional (SUNRAY-1D) large signal analysis model has been used for stability analysis of the helix SWS. The analysis on backward wave amplifier gain has been carried out as a function of the taper parameter and frequency parameter. The position and nature of tapering also affect the electronic efficiency as well as the start oscillation current. Hence, position and nature of tapering have been optimized.
关键词： backward wave oscillation (BWO),support rods,instability,Slow wave structure (SWS)
更新于2025-09-23 15:23:52
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A Slow-Wave Structure Optimization with Variable Helix Section Length in STWT Based on CI-NMCSO Algorithm
摘要： A novel slow-wave structure optimization method on Chaos-improved Normal mutation cat swarm optimization (CI-NMCSO) algorithm is proposed. Under the variable helix section length in STWT, the CI-NMCSO combined with 1D CHRISTINE code is used to calculate the best set of pitch distribution and section length with the objective function of electron beam efficiency improvement. Quantum particle swarm optimization (QPSO) and Cauchy mutated cat swarm optimization (CMCSO) algorithms are applied to make performance comparison. Experimental results show that the beam efficiency has been increased by CI-NMCSO from rated value 30% to 45.3%, and the values using CMCSO and QPSO are 41.8% and 36.5%, respectively, the convergence speed of CI-NMCSO is the fastest, only 16 iterations, while CMCSO and QPSO take 19 and 23 iterations, so the performance of CI-NMCSO is better than CMCSO and QPSO on both optimization precision and calculation speed in terms of slow-wave structure optimization, and is also superior to that with equal section length when the helix section length is variable.
关键词： space traveling-wave tube,electron beam efficiency,chaotic transformation,Slow-wave structure,normal mutation cat swarm optimization
更新于2025-09-23 15:22:29
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A Terahertz Traveling-Wave Tube Based on Defect Photonic Crystal Waveguide
摘要： A defect photonic crystal waveguide (DPCW) is presented as a slow-wave structure (SWS) for terahertz (THz) traveling-wave tube (TWT). Due to the characteristics of DPCW, the mode competition and backward wave are greatly depressed, improving the stability of TWT. The DPCW SWS has ?at dispersion characterization and high interaction impedance at 220 GHz. Simulation results show that saturated output power of 12.1 W, corresponding to a gain of 24.3 dB, and the 3-dB gain ripple within 20 GHz can be achieved at the center frequency of 220 GHz. The DPCW-TWT has a low working voltage at 9.52 kV compared to that of folded waveguide (FWG) SWS in this frequency band. The proposed DPCW for the THz regime is easy to fabricate and assemble using the modern fabrication processing technology.
关键词： terahertz,Defect photonic crystal waveguide (DPCW),traveling-wave tube (TWT),slow-wave structure (SWS)
更新于2025-09-23 15:21:01
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Investigation of angular log-periodic folded groove waveguide slow-wave structure for low voltage Ka-band TWT
摘要： In this paper, a novel angular log-periodic folded groove waveguide (ALFGW) slow-wave structure (SWS) has been investigated theoretically and experimentally for application in Ka-band traveling-wave tubes (TWTs). The dispersion relation for the ALFGW is derived analytically, and the dispersion characteristics are calculated for a Ka-band design. The designed SWS is fabricated using oxygen-free-copper that is silver electroplated. The measured cold-test parameters show good agreement with the simulation results, with S21 varying from ?2.7 dB to ?4.8 dB and S11 better than ?13.6 dB over the frequency range of 30–38 GHz. Simulations of beam–wave interactions using a 4850 V and 0.4 A sheet beam with a high aspect ratio of 28:1 indicate an output power of 128 W, corresponding to a maximum gain and electronic efficiency of 18.1 dB and 6.6%, respectively. Due to the log-periodic form, a higher output power, higher efficiency, wider bandwidth, and lower operating voltage are achieved as compared to a TWT based on the conventional folded groove waveguide (FGW) SWS. These results show that the proposed ALFGW SWS has good potential for application in relatively high-power wideband TWTs.
关键词： angular log-periodic folded groove waveguide,beam–wave interaction,slow-wave structure,Ka-band,traveling-wave tubes
更新于2025-09-19 17:13:59
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Compact Equal-Width Equal-Length Phase Shifter With Slow-Wave Half-Mode Substrate Integrated Waveguide for 5G Applications
摘要： The emerging fifth-generation (5G) wireless and mobile communications demand high-performance phase shifters to enable the multi-channel transmit/receive systems with phase control ability. In this work, a size-miniaturized wideband phase shifter based on slow-wave half-mode substrate integrated waveguide (SW-HMSIW) is presented. The proposed SW-HMSIW is consisting of conventional HMSIW section and periodically-patterned non-uniform microtrip polyline unit cells. Patterning polyline unit cells in HMSIW can effectively enhance the product of the equivalent permittivity and permeability of SW-HMSIW, so that the slow-wave effect can be exhibited and its associated size reduction will be further achieved. Moreover, lengths and widths of segments of the proposed polyline unit cell can influence the equivalent permittivity and permeability of the SW-HMSIW, and consequently change its phase constant and cutoff frequency. Hence, for a SW-HMSIW with a fixed physical length, an electrical length variation, i.e, phase shift, can be achieved as segments of the polyline employ various lengths or widths. Based on this principle, a wideband equal-width equal-length SW-HMSIW phase shifter is implemented. Measured results are in good agreement with simulated ones, with a phase shift of 90.5 ± 3 degree and a fractional bandwidth of 43.0% achieved. Compared with some similar reported works, the proposed one shows a size reduction more than 80% as well as good magnitude and phase deviations performance. Moreover, its miniaturized size and equal-width equal-length structure make it suitable for the complex multi-channel modules and networks of the 5G applications.
关键词： slow-wave structure,phase shifter,Effective medium approximation,size miniaturization,half-mode substrate integrated waveguide (HMSIW)
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - 1.0 THz Backward-Wave Oscillator Based on Novel Helical Groove Rectangular Waveguide
摘要： A novel helical groove rectangular waveguide slow wave structure (HGRW-SWS) is put forward to develop the lower operating voltage and high electron efficiency terahertz backward wave oscillator (BWO). The major advantage of the HGRW structure is its higher interaction impedance, lower ohm loss and lower operating voltage with respect to the typical SWSs such as folded waveguide SWS or double staggered grating SWS especially in the case of higher spatial harmonics. It is found that this kind of SWS can be operating on the n=-2 harmonic with the interaction impedance of more than 1.5 ohms from the analysis of the cold characteristics of the HGRW-SWS. Moreover, the beam-wave interaction results indicate that the BWO based on the HGRW SWS can produce the output power exceeding 0.657 W in the frequency range from 0.894 THz to 1.164 THz.
关键词： helical groove rectangular waveguide,slow wave structure,terahertz,interaction impedance,backward wave oscillator
更新于2025-09-12 10:27:22