Luqi Zhang

Study of High-Power Ka-Band Rectangular Double-Grating Sheet Beam BWO

It is attractive to use sheet beam vacuum devices to generate high frequency, high-power microwave radiation. In this paper, we present the numerical and experimental studies of a high-power Ka-band sheet electron beam backward wave oscillator (BWO), in which the double-grating rectangular waveguide is used as the slow wave structure (SWS) for its thermal and mechanical robustness. The fundamental mode of this kind of SWS is an antisymmetric mode which has an antisymmetric longitudinal field distribution and will nonsynchronously interact with the electron beam on two sides of the electron channel along the vertical direction. We put forward a method to overcome this trouble in this paper. To drive this BWO, a high-power sheet beam is used with a cross section of 30 mm

Investigation of 0.38 THz backward-wave oscillator based on slotted sine waveguide and pencil electron beam

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Novel W -Band Ridge-Loaded Folded Waveguide Traveling Wave Tube

1 mm. A thin graphite cathode is used for its superiority in producing a high current, high-quality electron beam. For an experimental electron beam of 141 kV and 1668 A, the output power of over 46.8 MW at 31.68 GHz is obtained, which corresponds to a beam–wave interaction efficiency of 19.9%. Compared with the conventional hollow beam BWO and the single-grating rectangular waveguide sheet beam BWO, the double-grating sheet beam BWOs efficiency is higher, which indicates that the double-grating sheet beam device is promising for producing millimeter wave radiation with high power and high efficiency.

Full-wave analysis of the high frequency characteristics of the sine waveguide slow-wave structure

A novel backward wave oscillator (BWO) is presented by utilizing a slotted sine waveguide with a pencil electron beam to produce the high power terahertz wave. The high frequency characteristics including dispersion properties, interaction impedances, and transmission characteristics of the slotted sine waveguide are analyzed in detail. The high frequency system including the output coupler, slow wave structure (SWS), and reflector are designed properly. A 3-D particle-in-cell mode is applied to predict the device performance of the BWO based on the novel SWS. The investigation results demonstrate that this device can generate over 8.05 W output power in the frequency range of 363.4–383.8 GHz by using a 30 mA pencil electron beam and adjusting the beam voltage from 20 kV to 32 kV.

A Ridge-Loaded Sine Waveguide for

A novel ridge-loaded folded waveguide slow-wave structure has been firstly employed to manufacture a W-band continuous wave traveling wave tube (TWT). This letter reports the processes of the design and experimental test for this TWT. From the experimental results, over 25-W output power are produced within the operation bandwidth from 93.1 to 94.8 GHz, which is in accordance with the simulation results.

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A theoretical model for calculation of the high frequency characteristics of the sine waveguide slow-wave structure (SWS) is proposed. The formulas of dispersion and interaction impedances of the hybrid modes are obtained by combining the Helmholtz equation with the appropriate boundary conditions. Using the full wave analysis method, it is proved that the periodic structures with a half-period shift followed leads to a pairwise closing of passbands characteristic of adjacent mode. The sine waveguide SWS for 0.22THz traveling wave tube (TWT) is chosen as an illustrative example to verify the validity of the theoretical model, and the calculation results of the dispersion curve and interaction impedance curve are consistent with the HFSS simulation results. In addition, the influences of dimensions of sine waveguide on the high frequency characteristics of +1st spatial harmonic wave are investigated by numerical calculation. The study indicates that the appropriate SWS parameters are helpful for improving ...

-Band Traveling-Wave Tube

A novel slow-wave structure (SWS), named ridge-loaded sine waveguide (RLSWG), has been proposed to develop the wideband high-power terahertz traveling-wave tube (TWT). The slow-wave characteristics of the RLSWG SWS, including dispersion properties and interaction impedance, are analyzed by using the 3-D electromagnetic simulation software Ansoft high frequency structure simulator (HFSS). From our calculation, the average interaction impedance of the RLSWG SWS at 0.22 THz is 42.2% higher than the conventional SWG SWS. Meanwhile, the simulation results demonstrate that the RLSWG SWS possesses low ohmic losses and reflection. Moreover, the particle-in-cell (PIC) simulation results reveal that, with the cylindrical electron beam of 20.9 kV and 45 mA, the output power and electron efficiency of the RLSWG TWT at the typical frequency of 0.22 THz can reach 52.1 W and 5.54%, respectively. In addition, the 3-dB bandwidth of the RLSWG TWT exceeds 25 GHz. Compared with the SWG TWT, the RLSWG TWT has the shorter tube length and can generate the larger output power.

Study for 140 GHz folded waveguide traveling wave tube with big electron tunnel

This paper mainly introduces the study for 140 GHz folded waveguide (FWG) traveling wave tube (TWT) with big electron tunnel. Through the high frequency simulation software and 3-D particle in cell (PIC) simulation, we get the structural parameters. By using these parameters, we fabricate the whole vacuum electron device (VED), including the slow wave structure, magnetic focusing system, input and output coupler and so on.

A novel microstrip meander-line slow wave structure for millimeter-wave TWT

A S-shaped microstrip meander-line slow wave structure is proposed for millimeter-wave sheet electron beam traveling-wave tube. The slow wave electromagnetic characteristics are calculated by HFSS. The results show that the structure has high interaction impedance and wide cold bandwidth. Meanwhile, the transmission loss is very small from the calculations of CST.

A triple-band planar monopole antenna for GPS/LTE/WLAN/Wi-Fi/WiMAX systems

A novel triple-band planar monopole antenna is presented in this report. By combing a C-shaped monopole, a U-shaped loop and a modified ground with a slot, three operating bands can be achieved. The measured results show that the 10-dB impedance bandwidths of the proposed antenna can cover multiple frequency bands, including 1.55–1.67 GHz, 2.2–3 GHz and 5.13–6 GHz, which can be applied to the GPS, LTE, WLAN, Wi-Fi and WiMAX systems. A prototype of the proposed antenna is fabricated and measured, the experimental results agree well with the simulated results.