Wenqiu Xie

Theory and Simulation of Arbitrarily Shaped Groove Staggered Double Grating Array Waveguide

A theoretical model for the arbitrarily shaped groove staggered double grating array waveguide (SDGAW) slow-wave structure is proposed in this paper. The boundary of the groove was approximately replaced by a series of steps and the formulas of dispersion and interaction impedance were obtained utilizing the field matching method combined with the continuity of transverse admittance. Considering the traditional single mode approximation (SMA) model is not so accurate for describing the high frequency (HF) characteristics, a multiple modes approximation (MMA) model is established, which takes account for the higher order terms in the grooves, thus greatly improves the accuracy of the numerical calculations. As an example, the HF characteristics of a cosine groove SDGAW for a 0.22-THz traveling wave tube were calculated utilizing the SMA model, the MMA model, and HFSS code, the results were compared and discussed. Comparison of the HF characteristics among several kinds of groove shaped SDGAWs has been made by numerical calculation.

Three dimensional nonlinear analysis of a single-grating rectangular waveguide Cerenkov maser

A three dimensional (3-D) nonlinear model for illustrating the beam-wave interaction in a single-grating rectangular waveguide sheet-beam Cerenkov maser is presented. The dynamical equations and the equations of motion are solved self-consistently to predict the device performance. Space-charge effects and Ohmic losses are considered in the model. A 1.03 THz backward wave oscillator and a 0.65 THz traveling wave tube are discussed as two illustrative examples.

Analytical solutions of dispersion characteristics for a coaxial staggered double grating array waveguide with step-shaped grooves

An analytical model for a coaxial staggered double grating array waveguide with step-shaped grooves is presented in this abstract, which has potential application in high-power THz travelling wave tubes (TWT). By using the field matching method combined with the transverse admittance matching method, the formulae for discussing high frequency characteristics of the slow wave structure (SWS), is obtained.

Analytical solutions of a coaxial staggered double-grating slow-wave structure

An analytical mode of a coaxial double-grating slow-wave structure (SWS) is obtained. Utilizing field matching method, in which the higher order terms of the field in the grooves are considered, the formulae for discussing the high frequency characteristics of the SWS, including dispersion and interaction impedance are given.

A wideband input/output structure for the staggered double grating sheet beam travelling wave tube

A wideband input/output structure for the staggered double grating sheet beam traveling wave tube (SBTWT) is designed, which has the merits of simple structure, low reflection and high isolation in a wide frequency band. A design example is given for a 94GHz sheet beam travelling wave tube, the CST-MWS simulation results show the S parameters are satisfactory.

High-Frequency Characteristics of the Axisymmetric TM Modes in a Coaxial Staggered Double-Grating Slow-Wave Structure

The formulas of dispersion and interaction impedances of the axisymmetric TM modes in a coaxial double-grating slow-wave structure (SWS) are obtained utilizing the field matching method, in which the higher order terms of the field in the grooves have been considered. The high-frequency characteristics of lowest two modes-the fundamental mode and the TM01 mode-in the SWS were discussed by adjusting its structure parameters. The calculated results show that the dispersion curve and the interaction impedance are in good agreement with those simulated by the CST-MWS code. In addition, the parameter analysis demonstrates that the rational selection of the position of the beam tunnel and the relative position of the upper and lower gratings are helpful for the development of the traveling-wave tube and the back-wave oscillator to improve the bandwidth and enhance the interaction impedance.

A three dimensional large signal model for sheet beam travelling wave tubes

A three-dimensional (3-D) frequency domain large signal code called SBTWT3D for illustrating the beam-wave interaction in the sheet beam traveling-wave tube (SBTWT) is presented. A 3-D nonlinear beam-wave interaction analysis for a W band SBTWT is performed and the calculation results are compared with those obtained from time-domain 3-D particle-in-cell simulations.

Analysis of high frequency characteristics for double-slot coupled cavity slow wave structure with a modified equivalent circuit

Discusses the modification of an equivalent circuit model of double-slot coupled cavity slow wave structure (CCSWS), including in-line and staggered with overlap ones. The model was investigated by comparing its calculation results of high frequency characteristics for a relative structure in X-band, with those obtained by full-wave electromagnetic software HFSS.

Linear analysis of a terahertz staggered double-grating arrays waveguide Cerenkov traveling wave amplifier

Based on a sheet electron beam propagating through the tunnel of a staggered double-grating arrays waveguide (SDGAW) slow-wave structure (SWS), a three dimensional linear theory for describing beam-wave interaction is presented, in which the higher order terms inside the groove were retained. With the optimized parameters, a 1THz SDGAW Cerenkov traveling wave amplifier (CTWA) may obtain a moderate net gain larger than 10dB/cm in 0.92THz to 1.145THz considering the serious Ohmic losses in THz frequency range.

Linear theory of double slot coupled cavity slow wave structure in TWT

A 3-D model of the double slot coupled cavity slow-wave structure (CCSWS) with a solid round electron beam for the beam-wave interaction is proposed in this abstract. Based on the “cold” dispersion, the “hot” dispersion equation is derived with the Borgnis potential function by using the field-matching method. Then, the formula of the linear gain is given.