Jianqiang Lai

W-Band 1-kW Staggered Double-Vane Traveling-Wave Tube

A design study for a W-band traveling-wave tube (TWT) using a staggered double-vane slow-wave structure combined with a sheet electron beam shows that an output power of over 1 kW should be possible. Numerical eigenmode calculations indicated that the structure has a strong longitudinal component of electric field for interaction with the electron beam. A novel input and output coupler was proposed that can produce good input and output matches. Finally, a TWT model with moderate dimensions was established. The particle-in-cell simulation results revealed that the tube can be expected to produce over 1 kW of peak power in the range from 90 to 95 GHz, assuming an RF input signal with a peak power of 0.15 W and a beam power of 10.3 kW. The corresponding conversion efficiency values vary from 9.87% to 12.15%, and the maximum gain is 39.2 dB at 93 GHz.

A 140 GHz staggered double vane backward wave oscillator

Staggered double vane structure was used as the slow wave circuit and sheet beam was applied to design a 140GHz backward wave oscillator. A transition structure for the circuit was proposed to minimize the attenuation and reflection of the system. Numerical calculation results demonstrated that the oscillator can produce the average output power in excess of 1 watt ranging from 134-146GHz with the beam current of 10mA and accelerating voltage around 20kV. Such design offers the microwave community a promising solution for short-millimeter wave radiation source.

Research of millimeter wave and Terahertz vacuum devices in NKLST-VE

This report gives a review about the study of the novel slow-wave structures and their application in millimeter wave and terahertz band vacuum devices in National Key Laboratory of Science and Technology on Vacuum Electronics(NKLST-VE) in China, including the development of some promising slow wave structures, the design and experiment work of the MM and Terahertz vacuum devices based upon some of these SWSs.

A staggered double vane circuit for millimeter wave traveling wave tube

Design of the staggered double vane slow wave structure (SWS) for two bands of traveling wave tube (TWT) amplifier, one for Ka-band and another one for W-band, has been presented in this paper. The high-frequency characteristics of this kind of structure were calculated by the HFSS eigenmode solver. And particle-in-cell method was carried out to investigate the amplification performance of this structure. Moreover, the experimental models, systems, and the results of this SWS for W-band TWT are exhibited in the end.

Rhombus-shaped microstrip meander-line slow-wave structure for 140 GHz traveling-wave tube

The simulation study on the rhombus-shaped microstrip meander-line slow-wave structure for 140 GHz traveling-wave tube iSs presented. The electromagnetic characteristics and beam-wave interaction of this structure are calculated. From our calculations, it is predicted that this rhombus-shaped microstrip meander-line traveling-wave tube is capable of delivering tens of watts output power.

A novel serpentine waveguide slow-wave structure with caps and posts

A novel serpentine waveguide slow wave structure (SWSWS) with caps and posts is proposed. The HFSS simulation results show that the interaction impedance is enhanced and the phase velocity is reduced over the normal SWSWS. The novel SWSWS is suitable for as the high-frequency structure of compact, linear beam devices.

Dielectric-lined azimuthally periodic circular waveguide for Ka-band TWT

The electron beam interaction in a novel slow-wave structure called dielectric-lined azimuthally periodic circular waveguide (DLAP-CW) is studied in Ka-band frame, which is a modified form of a conventional dielectric-lined circular waveguide (DL-CW). And the DLAP-CW has large beam aperture, good dispersion characteristics and easy fabrication. In this paper, the capability of beam-wave interaction when the DLAP-CW TWT operates in Ka-band is researched by CST PIC-solver. The particle-in-cell simulation results show that more than 1200W output power can be produced in DLAP-CW TWT interacting with high current annular beam with a low electron density 1.8 A/cm2. Furthermore, the gain at the central frequency of 30 GHz reaches 31 dB.

Recent advancements in sine waveguide for terahertz vacuum electron devices

Sine waveguide is a novel electromagnetic structure. The experimental and theoretical investigation work done on sine waveguide for terahertz vacuum electron devices is reported in this paper. One experimental model is fabricated in W-band, and its transmission loss is measured. At the same time, several terahertz traveling wave tube amplifiers and backward wave oscillators are designed in particle-in-cell method.

Progress on the V-band traveling-wave tube

In this paper, the recent research progress on the V-band traveling-wave tube in our laboratory is presented. Several robust full-metal slow-wave structures, including two circular beam structures and two sheet-beam structures, are investigated and employed to design the V-band traveling-wave tube. The corresponding operating characteristics are predicted by using the particle-in-cell method.

Virtual boundary element method for multistage depressed collector of traveling-wave tubes

In this study, virtual boundary element (VBE) method has been employed in multistage depressed collector (MDC) simulation for high efficiency traveling-wave tubes (TWTs). The basic idea of this method is establishing a mapping relation between the source on the real and virtual boundaries. When calculating the potential of the problem field, the virtual source on virtual boundary is only used, instead of the source on real boundary. We discussed the distance between the virtual and real boundaries and the discrete density of virtual boundary, which are closely related to the calculation accuracy. Based on the VBE method, a new computer aided design code CCAD is developed for the MDC system of high efficiency TWT. The results of simulations performed on an axisymmetric four-stage depressed collector are reported. The advantages of VBE method mainly lie in fast calculation and accurate solution. This is of benefit to designing high efficiency MDC thus developing high efficiency TWT, especially for space TWT.