Electronics

Editorial

Jump to: Research

4 pages, 173 KiB

Open AccessEditorial

High-Frequency Vacuum Electron Devices

by Jinjun Feng, Yubin Gong, Chaohai Du and Adrian Cross

Electronics 2022, 11(5), 817; https://doi.org/10.3390/electronics11050817 - 5 Mar 2022

Cited by 2 | Viewed by 2852

Abstract

Vacuum electron devices at frequencies of millimeter waves and terahertz play highly important roles in the modern high-data rate and broadband communication system, high-resolution detection and imaging, medical diagnostics, magnetically confined nuclear fusion, etc [...] Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

Research

Jump to: Editorial

11 pages, 4304 KiB

Open AccessFeature PaperArticle

Design of a Dual-Mode Input Structure for K/Ka-Band Gyrotron TWT

by Mengshi Ma, Qixiang Zhao, Kunshan Mo, Shuquan Zheng, Lin Peng, You Lv and Jinjun Feng

Electronics 2022, 11(3), 432; https://doi.org/10.3390/electronics11030432 - 30 Jan 2022

Cited by 10 | Viewed by 2440

Abstract

A dual-band gyrotron traveling wave amplifier (Gyro-TWT) can reduce the size, cost, and weight of a transmitter in dual-band radar and communication systems. In this paper, a dual-mode input coupler for K/Ka dual-band gyrotron traveling wave amplifier (Gyro-TWT) is designed. This structure is [...] Read more.

A dual-band gyrotron traveling wave amplifier (Gyro-TWT) can reduce the size, cost, and weight of a transmitter in dual-band radar and communication systems. In this paper, a dual-mode input coupler for K/Ka dual-band gyrotron traveling wave amplifier (Gyro-TWT) is designed. This structure is composed of two different types of input couplers, one is the coaxial input coupler for the Ka-band

{TE}_{2, 1}

Gyro-TWT and the other is a Y-type input coupler for the K-band

{TE}_{1, 1}

Gyro-TWT. For reducing the backward wave of the

{TE}_{2, 1}

mode reflecting into the Y-type input coupler to influence the operating bandwidth, a Bragg reflector with a strong mode selective characteristic is inserted between these two couplers, which can make the reflection coefficient of the

{TE}_{2, 1}

mode better than −1 dB and the phase matched in the whole bandwidth, and the transmission coefficient of the

{TE}_{1, 1}

mode can reach better than −1 dB. Based on the simulation results, the −1 dB bandwidth of the Ka-band

{TE}_{1, 0}^{⬜}

-

{TE}_{2, 1}^{◯}

mode input coupler reaches 3.32 GHz and the −1 dB bandwidth of K-band

{TE}_{1, 0}^{⬜}

-

{TE}_{1, 1}^{◯}

mode input coupler reaches 3.15 GHz. The designed dual-mode input coupler has the advantages of broad bandwidth and low loss and can be well used in dual-band Gyro-TWTs. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

12 pages, 5793 KiB

Open AccessArticle

Multiple Dielectric-Supported Ridge-Loaded Rhombus-Shaped Wideband Meander-Line Slow-Wave Structure for a V-Band TWT

by Yuxin Wang, Yang Dong, Xiangbao Zhu, Jingyu Guo, Duo Xu, Shaomeng Wang and Yubin Gong

Electronics 2022, 11(3), 405; https://doi.org/10.3390/electronics11030405 - 28 Jan 2022

Cited by 4 | Viewed by 2432

Abstract

A multiple dielectric-supported ridge-loaded rhombus-shaped meander-line (MDSRL-RSML) slow-wave structure (SWS) is proposed for a V-band wideband traveling wave tube (TWT). The high-frequency and transmission characteristics of the SWS are investigated. The proposed structure can realize stable output via attenuator and special phase-velocity jumping. [...] Read more.

A multiple dielectric-supported ridge-loaded rhombus-shaped meander-line (MDSRL-RSML) slow-wave structure (SWS) is proposed for a V-band wideband traveling wave tube (TWT). The high-frequency and transmission characteristics of the SWS are investigated. The proposed structure can realize stable output via attenuator and special phase-velocity jumping. Particle-in-cell (PIC) results indicate that, for a 7 kV, 0.1 A sheet-beam, the average output power can reach 60 W at 60 GHz and a 3 dB bandwidth of 9 GHz, with the corresponding gain and electron efficiency of 30.8 dB and 17.2%, respectively. Compared with the dielectric-supported rhombus-shape meander-line (DS-RSML) SWS, the proposed structure has a wider bandwidth, higher gain, more stable structure, and better heat dissipation ability, which make it a good candidate source in millimeter-wave communications. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

9 pages, 2280 KiB

Open AccessArticle

A Vacuum Transistor Based on Field-Assisted Thermionic Emission from a Multiwalled Carbon Nanotube

by Yidan He, Zhiwei Li, Shuyu Mao, Fangyuan Zhan and Xianlong Wei

Electronics 2022, 11(3), 399; https://doi.org/10.3390/electronics11030399 - 28 Jan 2022

Cited by 5 | Viewed by 4537

Abstract

Vacuum triodes have been scaled down to the microscale on a chip by microfabrication technologies to be vacuum transistors. Most of the reported devices are based on field electron emission, which suffer from the problems of unstable electron emission, poor uniformity, and high [...] Read more.

Vacuum triodes have been scaled down to the microscale on a chip by microfabrication technologies to be vacuum transistors. Most of the reported devices are based on field electron emission, which suffer from the problems of unstable electron emission, poor uniformity, and high requirement for operating vacuum. Here, to overcome these problems, a vacuum transistor based on Field-Assisted thermionic emission from individual carbon nanotubes is proposed and fabricated using microfabrication technologies. The carbon nanotube vacuum transistor exhibits an ON/OFF current ratio as high as 10⁴ and a subthreshold slope of ~4 V·dec⁻¹. The gate controllability is found to be strongly dependent on the distance between the collector electrodes and electron emitter, and a device with the distance of 1.5 μm shows a better gate controllability than that with the distance of 0.5 μm. Benefiting from Field-Assisted thermionic emission mechanism, electric field required in our devices is about one order of magnitude smaller than that in the devices based on field electron emission, and the surface of the emitters shows much less gas molecule absorption than cold field emitters. These are expected to be helpful for improving the stability and uniformity of the devices. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

9 pages, 18810 KiB

Open AccessArticle

Broadband-Printed Traveling-Wave Tube Based on a Staggered Rings Microstrip Line Slow-Wave Structure

by Ruichao Yang, Lingna Yue, Jin Xu, Pengcheng Yin, Jinjing Luo, Hexin Wang, Dongdong Jia, Jian Zhang, Hairong Yin, Jinchi Cai, Guo Guo, Guoqing Zhao, Wenxiang Wang, Dazhi Li and Yanyu Wei

Electronics 2022, 11(3), 384; https://doi.org/10.3390/electronics11030384 - 27 Jan 2022

Cited by 4 | Viewed by 2811

Abstract

To increase the output power of microstrip line traveling-wave tubes, a staggered rings microstrip line (SRML) slow-wave structure (SWS) based on a U-shaped mender line (U-shaped ML) SWS and a ring-shaped microstrip line (RML) SWS has been proposed in this paper. Compared with [...] Read more.

To increase the output power of microstrip line traveling-wave tubes, a staggered rings microstrip line (SRML) slow-wave structure (SWS) based on a U-shaped mender line (U-shaped ML) SWS and a ring-shaped microstrip line (RML) SWS has been proposed in this paper. Compared with U-shaped ML SWS and RML SWS, SRML SWS has a wider transverse width, which means SRML SWS has a larger area for beam–wave interaction. The simulation results show that SRML SWS has a wider bandwidth than U-shaped ML SWS and a lower phase velocity than RML SWS. Input/output couplers, which consist of microstrip probes and transition sections, have been designed to transmit signals from a rectangular waveguide to the SWS; the simulation results present that the designed input/output structure has good transmission characteristics. Particle-in-cell (PIC) simulation results indicate that the SRML TWT has a maximum output of 322 W at 32.5 GHz under a beam voltage of 9.7 kV and a beam current of 380 mA, and the corresponding electronic efficiency is around 8.74%. The output power is over 100 W in the frequency range of 27 GHz to 38 GHz. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

11 pages, 1040 KiB

Open AccessArticle

Investigation on High-Efficiency Beam-Wave Interaction for Coaxial Multi-Beam Relativistic Klystron Amplifier

by Limin Sun, Hua Huang, Shifeng Li, Zhengbang Liu, Hu He, Qifan Xiang, Ke He and Xianghe Fang

Electronics 2022, 11(2), 281; https://doi.org/10.3390/electronics11020281 - 17 Jan 2022

Cited by 7 | Viewed by 2952

Abstract

To significantly improve the electronic efficiency of coaxial multi-beam relativistic klystron amplifier (CMB-RKA), the physical process of beam-wave interaction and parameters that affect efficiency was studied. First, the high efficiency of beam-wave interaction was discussed by simulating the efficiency versus the parameters (frequency [...] Read more.

To significantly improve the electronic efficiency of coaxial multi-beam relativistic klystron amplifier (CMB-RKA), the physical process of beam-wave interaction and parameters that affect efficiency was studied. First, the high efficiency of beam-wave interaction was discussed by simulating the efficiency versus the parameters (frequency of cavity, drift tube length between cavities, and external quality factor of output cavity), in the one-dimensional (1-D) large-signal simulation software. Moreover, the further physical process of beam-wave interaction was analyzed through simulating the current modulation factor and the number of particles at the entrance of the output cavity, in the three-dimensional (3-D) particle in cell simulation software. Last, with the optimal parameters in 3-D simulations, the CMB-RKA, which has 14 electron beams with a total current of 4.2 kA (14 × 300 A), can generate an output power of 1.02 GW with a saturation gain of 55.6 dB and an efficiency of 48.7%, when beam voltage is 500 kV, which indicated the CMB-RKA can achieve high efficiency for high-power microwave radiation. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

10 pages, 3506 KiB

Open AccessArticle

Investigation of a Miniaturized E-Band Cosine-Vane Folded Waveguide Traveling-Wave Tube for Wireless Communication

by Kexin Ma, Jun Cai and Jinjun Feng

Electronics 2021, 10(24), 3054; https://doi.org/10.3390/electronics10243054 - 7 Dec 2021

Cited by 2 | Viewed by 2221

Abstract

To realize the miniaturization of E-band traveling-wave tubes (TWTs), the size analysis and optimization design were carried out based on an improved cosine-vane folded waveguide (CV-FWG) slow-wave structure (SWS) that operates in a low voltage. In addition, a novel miniaturized T-shaped coupler was [...] Read more.

To realize the miniaturization of E-band traveling-wave tubes (TWTs), the size analysis and optimization design were carried out based on an improved cosine-vane folded waveguide (CV-FWG) slow-wave structure (SWS) that operates in a low voltage. In addition, a novel miniaturized T-shaped coupler was proposed to achieve a good voltage standing wave rate (VSWR) in a broad bandwidth. The coupler length was reduced by as much as 77% relative to an original design. With higher coupling impedance, the radius and length of the shortened SWS were optimized as 1.3 mm and 50 mm, respectively. Using microwave tube simulator suit (MTSS) and CST particle studio (PS), 3D beam–wave simulations at 9400 V, 20 mA predicted a gain of 20 dB and a saturated output power of 9 W. The simulation results for CV-FWG TWTs were compared with conventional FWG TWTs from 81 GHz to 86 GHz, showing significant performance advantages with excellent flatness for high-rate wireless communication in the future. The CV-FWG SWS circuit will be fabricated by 3D printing, and this work is underway. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

10 pages, 5109 KiB

Open AccessFeature PaperArticle

Design and Experiments of the Sheet Electron Beam Transport with Periodic Cusped Magnetic Focusing for Terahertz Traveling-Wave Tubes

by Changqing Zhang, Pan Pan, Xueliang Chen, Siming Su, Bowen Song, Ying Li, Suye Lü, Jun Cai, Yubin Gong and Jinjun Feng

Electronics 2021, 10(24), 3051; https://doi.org/10.3390/electronics10243051 - 7 Dec 2021

Cited by 8 | Viewed by 2915

Abstract

The successful transport of a sheet electron beam under the periodic cusped magnet (PCM) focusing at the terahertz frequencies is reported. The sheet beam with a current density of 285 A/cm² is intended for the developing G-band sheet-beam traveling-wave tube (TWT) whose [...] Read more.

The successful transport of a sheet electron beam under the periodic cusped magnet (PCM) focusing at the terahertz frequencies is reported. The sheet beam with a current density of 285 A/cm² is intended for the developing G-band sheet-beam traveling-wave tube (TWT) whose operating voltage is nominally 24.5 kV. A beamstick was developed to validate the design of the electron optics system, which is considered as the most challenging part for developing a sheet-beam device. A beam transmission ratio of 81% is achieved over a distance of 37.5 mm at a cathode voltage of −25.0 kV. The total current and the collector current were measured to be 125 and 102 mA, respectively. The experimental results are promising, demonstrating that the PCM scheme is capable of focusing a high-current-density sheet beam and hence can find use in the terahertz TWTs, offering the advantages of compact size and light weight. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

9 pages, 3463 KiB

Open AccessArticle

A 340 GHz High-Power Multi-Beam Overmoded Flat-Roofed Sine Waveguide Traveling Wave Tube

by Jinjing Luo, Jin Xu, Pengcheng Yin, Ruichao Yang, Lingna Yue, Zhanliang Wang, Lin Xu, Jinjun Feng, Wenxin Liu and Yanyu Wei

Electronics 2021, 10(23), 3018; https://doi.org/10.3390/electronics10233018 - 3 Dec 2021

Cited by 7 | Viewed by 1807

Abstract

A phase shift that is caused by the machining errors of independent circuits would greatly affect the efficiency of the power combination in traditional multi-beam structures. In this paper, to reduce the influence of the phase shift and improve the output power, a [...] Read more.

A phase shift that is caused by the machining errors of independent circuits would greatly affect the efficiency of the power combination in traditional multi-beam structures. In this paper, to reduce the influence of the phase shift and improve the output power, a multi-beam shunted coupling sine waveguide slow wave structure (MBSC-SWG-SWS) has been proposed, and a multi-beam overmoded flat-roofed SWG traveling wave tube (TWT) based on the MBSC-SWG-SWS was designed and analyzed. A TE₁₀-TE₃₀ mode convertor was designed as the input/output coupler in this TWT. The results of the 3D particle-in-cell (PIC) simulation with CST software show that more than a 50 W output power can be produced at 342 GHz, and the 3 dB bandwidth is about 13 GHz. Furthermore, the comparison between the single-beam sine waveguide (SWG) TWT and the multi-beam overmoded SWG TWT indicates that the saturated output power of the multi-beam overmoded SWG TWT is three times more than that of the single beam SWG TWT. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

8 pages, 2245 KiB

Open AccessArticle

Broadband and Integratable 2 × 2 TWT Amplifier Unit for Millimeter Wave Phased Array Radar

by Guo Guo, Zhenlin Yan, Zhenzhen Sun, Jianwei Liu, Ruichao Yang, Yubin Gong and Yanyu Wei

Electronics 2021, 10(22), 2808; https://doi.org/10.3390/electronics10222808 - 16 Nov 2021

Cited by 4 | Viewed by 1769

Abstract

A novel power amplifier unit for a phased array radar with 2 × 2 output ports for a vacuum electron device is proposed. Double parallel connecting microstrip meander-lines are employed as the slow-wave circuits of a large power traveling wave tube operate in [...] Read more.

A novel power amplifier unit for a phased array radar with 2 × 2 output ports for a vacuum electron device is proposed. Double parallel connecting microstrip meander-lines are employed as the slow-wave circuits of a large power traveling wave tube operate in a Ka-band. The high frequency characteristics, the transmission characteristics, and the beam–wave interaction processes for this amplifier are simulated and optimized. For each output port of one channel, the simulation results reveal that the output power, saturated gain, and 3-dB bandwidth can reach 566 W, 27.5 dB, and 7 GHz, respectively. Additionally, the amplified signals of four output ports have favorable phase congruency. After fabrication and assembly, transmission tests for the 80-period model are performed preliminarily. The tested “cold” S-parameters match well with the simulated values. This type of integratable amplifier combined with a vacuum device has broad application prospects in the field of high power and broad bandwidth on a millimeter wave phased array radar. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

12 pages, 2828 KiB

Open AccessArticle

Green’s Functions of Multi-Layered Plane Media with Arbitrary Boundary Conditions and Its Application on the Analysis of the Meander Line Slow-Wave Structure

by Zheng Wen, Jirun Luo and Wenqi Li

Electronics 2021, 10(21), 2716; https://doi.org/10.3390/electronics10212716 - 8 Nov 2021

Cited by 1 | Viewed by 2094

Abstract

A method was proposed for solving the dyadic Green’s functions (DGF) and scalar Green’s functions (SGF) of multi-layered plane media in this paper. The DGF and SGF were expressed in matrix form, where the variables of the boundary conditions (BCs) can be separated [...] Read more.

A method was proposed for solving the dyadic Green’s functions (DGF) and scalar Green’s functions (SGF) of multi-layered plane media in this paper. The DGF and SGF were expressed in matrix form, where the variables of the boundary conditions (BCs) can be separated in matrix form. The obtained DGF and SGF are in explicit form and suitable for arbitrary boundary conditions, owing to the matrix form expression and the separable variables of the BCs. The Green’s functions with typical BCs were obtained, and the dispersion characteristic of the meander line slow-wave structure (ML-SWS) is analyzed based on the proposed DGF. The relative error between the theoretical results and the simulated ones with different relative permittivity is under 3%, which demonstrates that the proposed DGF is suitable for electromagnetic analysis to complicated structure including the ML-SWS. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

9 pages, 10159 KiB

Open AccessArticle

Inverse Design of a Microstrip Meander Line Slow Wave Structure with XGBoost and Neural Network

by Yijun Zhu, Yang Xie, Ningfeng Bai and Xiaohan Sun

Electronics 2021, 10(19), 2430; https://doi.org/10.3390/electronics10192430 - 7 Oct 2021

Cited by 6 | Viewed by 2088

Abstract

We present a new machine learning (ML) deep learning (DL) synthesis algorithm for the design of a microstrip meander line (MML) slow wave structure (SWS). Exact numerical simulation data are used in the training of our network as a form of supervised learning. [...] Read more.

We present a new machine learning (ML) deep learning (DL) synthesis algorithm for the design of a microstrip meander line (MML) slow wave structure (SWS). Exact numerical simulation data are used in the training of our network as a form of supervised learning. The learning results show that the training mean squared error is as low as 5.23 × 10⁻² when using 900 sets of data. When the desired performance is reached, workable geometry parameters can be obtained by this algorithm. A D-band MML SWS with 20 GHz bandwidth at 160 GHz center frequency is then designed using the auto-design neural network (ADNN). A cold test shows that its phase velocity varies by 0.005 c, and the transmission rate of a 50-period SWS is greater than −5 dB with the reflectivity below −15 dB when the frequency is from 150 to 170 GHz. Particle-in-cell (PIC) simulation also illustrates that a maximum power of 3.2 W is reached at 160 GHz with 34.66 dB gain and output power greater than 1 W from 152 to 168 GHz. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

10 pages, 2708 KiB

Open AccessFeature PaperArticle

Study of an Attenuator Supporting Meander-Line Slow Wave Structure for Ka-Band TWT

by Hexin Wang, Shaomeng Wang, Zhanliang Wang, Xinyi Li, Tenglong He, Duo Xu, Zhaoyun Duan, Zhigang Lu, Huarong Gong and Yubin Gong

Electronics 2021, 10(19), 2372; https://doi.org/10.3390/electronics10192372 - 28 Sep 2021

Cited by 7 | Viewed by 2042

Abstract

An attenuator supporting meander-line (ASML) slow wave structure (SWS) is proposed for a Ka-band traveling wave tube (TWT) and studied by simulations and experiments. The ASML SWS simplifies the fabrication and assembly process of traditional planar metal meander-lines (MLs) structures, by employing an [...] Read more.

An attenuator supporting meander-line (ASML) slow wave structure (SWS) is proposed for a Ka-band traveling wave tube (TWT) and studied by simulations and experiments. The ASML SWS simplifies the fabrication and assembly process of traditional planar metal meander-lines (MLs) structures, by employing an attenuator to support the ML on the bottom of the enclosure rather than welding them together on the sides. To reduce the surface roughness of the molybdenum ML caused by laser cutting, the ML is coated by a thin copper film by magnetron sputtering. The measured S₁₁ of the ML is below −20 dB and S₂₁ varies around −8 dB to −12 dB without the attenuator, while below −40 dB with the attenuator. Particle-in-cell (PIC) simulation results show that with a 4.4-kV, 200-mA sheet electron beam, a maximum output power of 126 W is obtained at 38 GHz, corresponding to a gain of 24.1 dB and an electronic efficiency of 14.3%, respectively. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

8 pages, 6855 KiB

Open AccessArticle

A New Method to Focus SEBs Using the Periodic Magnetic Field and the Electrostatic Field

by Pengcheng Yin, Jin Xu, Lingna Yue, Ruichao Yang, Hairong Yin, Guoqing Zhao, Guo Guo, Jianwei Liu, Wenxiang Wang, Yubin Gong, Jinjun Feng, Dazhi Li and Yanyu Wei

Electronics 2021, 10(17), 2118; https://doi.org/10.3390/electronics10172118 - 31 Aug 2021

Cited by 1 | Viewed by 2043

Abstract

In this paper, a novel method, named PM-E, to focus the sheet electron beam (SEB) is proposed. This new method consists of a periodic magnetic field and an electrostatic field, which are used to control the thickness and width of the SEB, respectively. [...] Read more.

In this paper, a novel method, named PM-E, to focus the sheet electron beam (SEB) is proposed. This new method consists of a periodic magnetic field and an electrostatic field, which are used to control the thickness and width of the SEB, respectively. The PM-E system utilizes this electrostatic field to replace the unreliable

B_{y, o f f}

, which is a tiny transverse magnetic field in the PCM that confines the SEB’s width. Moreover, the horizontal focusing force of the PM-E system is more uniform than that of the conventional PCM, and the transition distance of the former is shorter than that of the latter. In addition, the simulation results demonstrate the ability of the PM-E system to resist the influence of the assembly error. Furthermore, in the PM-E system, the electric field can be conveniently changed to correct the deflection of the SEB’s trajectory and to improve the quality of the SEB. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

11 pages, 3021 KiB

Open AccessArticle

A G-Band High Output Power and Wide Bandwidth Sheet Beam Extended Interaction Klystron Design Operating at TM₃₁ with 2π Mode

by Shasha Li, Feng Zhang, Cunjun Ruan, Yiyang Su and Pengpeng Wang

Electronics 2021, 10(16), 1948; https://doi.org/10.3390/electronics10161948 - 12 Aug 2021

Cited by 6 | Viewed by 2243

Abstract

In this paper, we propose a high-order mode sheet beam extended interaction klystron (EIK) operating at G-band. Through the study of electric field distribution, we choose TM₃₁ 2π mode as the operating mode. The eigenmode simulation shows that the resonant frequency of [...] Read more.

In this paper, we propose a high-order mode sheet beam extended interaction klystron (EIK) operating at G-band. Through the study of electric field distribution, we choose TM₃₁ 2π mode as the operating mode. The eigenmode simulation shows that the resonant frequency of the modes adjacent to the operating mode is far away from the central frequency, so there is almost no mode competition in our high mode EIK. In addition, by studying the sensitivity of the related geometry parameters, we conclude that the height of the coupling cavity has a great influence on the effective characteristic impedance, and the width of the gap mainly affects the working frequency. Therefore, it is necessary to strictly control the fabrication tolerance within 2 μm. Finally, the RF circuit using six barbell multi-gap cavities is determined, with five gaps for the input cavity and idler cavities and seven gaps for the output cavity. To expand the bandwidth, the stagger tuning method is adopted. Under the conditions of a voltage of 16.5 kV, current of 0.5 A and input power of 0.2 W, the peak output power of 650 W and a 3-dB bandwidth of 700 MHz are achieved without any self-oscillation. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

13 pages, 18086 KiB

Open AccessArticle

Linearly Polarized High-Purity Gaussian Beam Shaping and Coupling for 330 GHz/500 MHz DNP-NMR Application

by Xingchen Yang, Chaohai Du, Ziwen Zhang, Juanfeng Zhu, Tiejun Huang and Pukun Liu

Electronics 2021, 10(13), 1508; https://doi.org/10.3390/electronics10131508 - 22 Jun 2021

Cited by 1 | Viewed by 2096

Abstract

Terahertz waves generated by vacuum electron devices have been successfully applied in dynamic nuclear polarization enhanced nuclear magnetic resonance (DNP-NMR) technology to significantly enhance the sensitivity of high-field NMR. To reduce the magnetic field interference, the high-power terahertz wave source and the NMR [...] Read more.

Terahertz waves generated by vacuum electron devices have been successfully applied in dynamic nuclear polarization enhanced nuclear magnetic resonance (DNP-NMR) technology to significantly enhance the sensitivity of high-field NMR. To reduce the magnetic field interference, the high-power terahertz wave source and the NMR spectrometer need to be separated by a few meters apart. Corrugated horns and directional couplers are key components for shaping high linearly polarized terahertz Gaussian beam and accurately coupling electromagnetic power in the transmission system. In this paper, a corrugated TE₁₁-HE₁₁ mode converter and a three-port directional coupler realized by its inner cylindrical wire array are proposed for a 330 GHz/500 MHz DNP-NMR system. The output mode of the mode converter presents a characteristic of highly linear polarization, which is 98.8% at 330 GHz for subsequent low loss transmission. The designed three-port directional coupler can produce approximately −33 dB electromagnetic wave power on port 3 in the frequency range between 300–360 GHz stably, which can be used to measure the electromagnetic wave power of the transmission line in real-time. The designed mode converter and direction coupler can be installed and replaced easily in the corrugated waveguide transmission system. Full article

(This article belongs to the Special Issue High-Frequency Vacuum Electron Devices)

► Show Figures

Figure 1

Journal Menu

Journal Browser

High-Frequency Vacuum Electron Devices

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Published Papers (16 papers)

Editorial

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI