Showing papers by "Yanyu Wei published in 2018"
TL;DR: In this article, the authors presented two configurations to reduce the mutual coupling (MC) between two microstrip patch antenna elements, where one ML is inserted in the slot of the ground and a maximum MC reduction of 39 dB throughout the −10 dB bandwidth is achieved.
Abstract: Meander lines (MLs) in two configurations are presented to reduce the mutual coupling (MC) between two microstrip patch antenna elements. Inserting a slot in the ground plane between the antenna elements is a simple method to reduce the MC, while adding the MLs in the slot of the ground can further reduce the MC. In the first configuration, one ML is inserted in the slot of the ground and a maximum MC reduction of 39 dB throughout the −10 dB bandwidth is achieved. What’s more, the radiation patterns are not changed compared with the dual-element microstrip antenna array with a slotted ground. For the second configuration, two MLs are added in the slot of the ground. It is found that a maximum isolation of 53 dB can be obtained. However, the radiation patterns are slightly changed compared with the dual-element microstrip antenna array with a slot in the ground. Meanwhile, the measured peak gain and efficiency of the dual-element microstrip antenna array in the two configurations are given. Along with this paper, several prototypes have been fabricated and measured. The simulated results are in good accordance with the measurements, which are presented to verify that MC reduction can be achieved between microstrip antenna elements by adding the MLs in the slotted ground.
22 citations
TL;DR: In this article, a planar monopole antenna with dual-band circularly polarisation (CP) was proposed, which consists of a modified L-shaped monopole, an inverted-L strip, and a modified ground.
Abstract: A novel planar monopole antenna with dual-band circularly polarisation (CP) is presented here. The antenna consists of a modified L-shaped monopole, an inverted-L strip, and a modified ground. The utilisation of the modified L-shaped monopole not only generates dual-band operation, but also excites CP radiation in the lower band. In order to achieve CP in the upper band, a parasitic inverted-L strip is added on the top plane of the substrate and a modified ground is designed. The proposed antenna has been fabricated and tested, the measured -10 dB reflection coefficient bandwidths are 370 MHz (2.38-2.85 GHz) in the lower band and 2330 MHz (4.05-6.38 GHz) in the upper band. The measured corresponding 3 dB axial ratio (AR) bandwidths are 610 MHz (2.39-3 GHz) and 850 MHz (5.15-6 GHz), respectively. The overlapped -10 dB reflection coefficient and AR bandwidths can totally cover the WLAN bands, Wi-Fi bands, Bluetooth band, and partly cover the WiMAX bands. The proposed antenna owns bidirectional radiation characteristic and reasonable gain at both the lower band and the upper band.
20 citations
TL;DR: In this paper, a flat-roofed sine waveguide slow-wave structure (FRSWG-SWS) was proposed for a W-band sheet electron beam (SEB) traveling-wave tube (TWT) based on flat-Roofed Sine Waveguide (SWG) structure.
Abstract: A W-band sheet electron beam (SEB) traveling-wave tube (TWT) based on flat-roofed sine waveguide slow-wave structure (FRSWG-SWS) is proposed. The sine wave of the metal grating is replaced by a flat-roofed sine wave around the electron beam tunnel. The slow-wave characteristics including the dispersion properties and interaction impedance have been investigated by using the eigenmode solver in the 3-D electromagnetic simulation software Ansoft HFSS. Through calculations, the FRSWG SWS possesses the larger average interaction impedance than the conventional sine waveguide (SWG) SWS in the frequency range of 86-110 GHz. The beam-wave interaction was studied and particle-in-cell simulation results show that the SEB TWT can produce output power over 120 W within the bandwidth ranging from 90 to 100 GHz, and the maximum output power is 226 W at typical frequency 94 GHz, corresponding electron efficiency of 5.89%.
20 citations
24 Apr 2018
TL;DR: In this article, the authors proposed the use of the meander line (ML) as a parasitic configuration to reduce the mutual coupling between two microstrip patch antenna elements to achieve a maximum MC reduction of 40dB.
Abstract: In this paper, meander line (ML) as a parasitic configuration is introduced to reduce the mutual coupling (MC) between two microstrip patch antenna elements. Inserting a slot in the middle of ground plane is a simple method to reduce the MC, by adding the ML in the proper position in the slot can further reduce the MC. Along with this letter, several prototypes have been fabricated and measured. The simulated results show a close agreement with the experimental results, which show that a maximum MC reduction of 40dB can be achieved.
19 citations
TL;DR: In this paper, a ridge-loaded folded rectangular groove waveguide has been proposed for developing the wideband high-power terahertz (THz) traveling-wave tube (TWT), which can successfully suppress the selfexcited oscillations and keep the harmonics to a very low level.
Abstract: A novel slow-wave structure (SWS) called ridge-loaded folded rectangular groove waveguide has been proposed for developing the wideband high-power terahertz (THz) traveling-wave tube (TWT). A new kind of attenuator suitable for this kind of SWS has also been proposed, which can successfully suppress the self-excited oscillations and keep the harmonics to a very low level. An input and output waveguide transition structure which is appropriate for this new kind of SWS is put forward. It can be found from the simulation results that the ridge-loaded SWS can enhance the electric field intensity in the electron beam tunnel so that the average interaction impedance of this ridge-loaded folded rectangular groove waveguide SWS at 0.34 THz is 30.1% higher than that of the folded rectangular groove waveguide SWS. Moreover, the particle-in-cell simulation results reveal that with the sheet electron beam parameters of 27 kV and the 250 mA, the average output power, the gain, and the electronic efficiency of the ridge-loaded folded rectangular groove waveguide TWT at the frequency of 0.34 THz can reach 39 W, 26.99 dB, and 0.59%, respectively. Therefore, the ridge-loaded folded rectangular groove waveguide SWS should be considered as a promising slow-wave circuit for high-power wideband THz radiation source.
18 citations
TL;DR: In this article, a dual-sheet-beam planar dielectric-rod-support uniform metallic meander line slow-wave structure (SWS) for high-efficiency Ka-band traveling wave tube (TWT) is proposed.
Abstract: A dual-beam planar dielectric-rod-support uniform metallic meander line slow-wave structure (SWS) for high-efficiency Ka-band traveling wave tube (TWT) is proposed in this paper. Two dielectric rods are placed on both sides of metallic meander line to support it, instead of the dielectric substrate in the conventional microstrip meander line. Furthermore, it can not only solve the problem of the electron charge accumulation on microstrip but also leads to a bigger interaction impedance. According to particle-in-cell simulation results, a dual-sheet-beam planar dielectric-rod-support uniform metallic meander line TWT can get an output power of 330.2 W at 38 GHz under the case of 10.6 kV beam voltage and 0.2 A beam current. The corresponding maximum gain and electron efficiency are 23.4 dB and 15.5%, respectively, where the length of whole SWS is only 20 mm.
16 citations
TL;DR: In this paper, an innovative complementary electric split-ring resonator metamaterial (MTM) structure applied as the slow-wave circuit for a cascade backward-wave oscillator (CBWO) operating in C-band is studied.
Abstract: An innovative complementary electric split-ring resonator metamaterial (MTM) structure applied as the slow-wave circuit for a cascade backward-wave oscillator (CBWO) operating in C-band is studied in this paper. The idea of a drift tube in a multiresonant cavity extended interaction klystron is borrowed to design a novel backward-wave oscillator (BWO). The construction of this device features two BWOs separated by a short cutoff waveguide for permitting the flow of the electron beam and stopping the electromagnetic wave. The high-frequency characteristics are analyzed and optimized by using a high-frequency structure simulator and computer simulation technology (CST). Meanwhile, the S-parameter retrieval approach is used to retrieve the effective permittivity and permeability. In addition, the CST code is adopted to investigate the performance of the MTM-based CBWO. The particle-in-cell simulation results show that the novel CBWO is capable of achieving over 51.77% electronic efficiency from 4.8344 to 4.8687 GHz. Meanwhile, the maximum electronic efficiency can reach 82.44%, corresponding to a peak output power of 14.51 MW at 4.8466 GHz. These results indicate that the MTM-based CBWO proposed in this paper has the characteristic of miniaturization, manufacturability, and high electronic efficiency.
16 citations
08 Jul 2018
TL;DR: A compact dual-band dual-element multiple-input-multiple-output (MIMO) antenna for wireless local area network (WLAN) and Wireless-Fidelity (Wi-Fi) applications is presented in this report.
Abstract: A compact dual-band dual-element multiple-input-multiple-output (MIMO) antenna for wireless local area network (WLAN) and Wireless-Fidelity (Wi-Fi) applications is presented in this report. The proposed antenna has a simple planar structure and occupies a small area of 13. S×32mm2. An L-shaped open-ended slot and an L-shaped micros trip line are used as quarter-wavelength and half wavelength radiators, respectively. The operating band of the proposed antenna are from 2.3-2.49 GHz and S.1-S.S6GHz. The wide slot in the middle of the ground is used to achieve good isolation at both bands.
15 citations
TL;DR: In this article, a theoretical model for linear analysis of the beam-wave interaction in a sine waveguide (SWG) with slow-wave structure was proposed, and the effects of voltage, current, beam thickness, period, and oscillation amplitude on the linear gain and bandwidth were calculated.
Abstract: A theoretical model is proposed for linear analysis of the beam–wave interaction in a sine waveguide (SWG) with slow-wave structure. The field expressions and “hot” dispersion equation are obtained by means of field matching. The ohmic loss and attenuation constant due to imperfect conductors are also derived using the theoretical model. Moreover, the effects of voltage, current, beam thickness, period, and oscillation amplitude on the linear gain and bandwidth are calculated. The results indicate a peak gain and 3-dB bandwidth of 6.82 dB/cm and 19.5%, respectively, for a 0.22-THz SWG traveling-wave tube upon selecting reasonable structural parameters and electron-beam dimensions. Furthermore, by considering the ohmic losses for the finite conductivities of 5.8 × 107 S/m and 2.2 × 107 S/m, the theoretical results are compared with those of particle-in-cell simulations performed using Computer Simulation Technology Particle Studio.A theoretical model is proposed for linear analysis of the beam–wave interaction in a sine waveguide (SWG) with slow-wave structure. The field expressions and “hot” dispersion equation are obtained by means of field matching. The ohmic loss and attenuation constant due to imperfect conductors are also derived using the theoretical model. Moreover, the effects of voltage, current, beam thickness, period, and oscillation amplitude on the linear gain and bandwidth are calculated. The results indicate a peak gain and 3-dB bandwidth of 6.82 dB/cm and 19.5%, respectively, for a 0.22-THz SWG traveling-wave tube upon selecting reasonable structural parameters and electron-beam dimensions. Furthermore, by considering the ohmic losses for the finite conductivities of 5.8 × 107 S/m and 2.2 × 107 S/m, the theoretical results are compared with those of particle-in-cell simulations performed using Computer Simulation Technology Particle Studio.
12 citations
07 May 2018
TL;DR: In this article, a small and compact microstrip-fed monopole antenna, which consists of a rectangular patch and a truncated ground plane, is presented for ultra wideband (UWB) application.
Abstract: A small and compact microstrip-fed monopole antenna, which consists of a rectangular patch and a truncated ground plane, is presented for ultra wideband (UWB) application. The antenna occupies a compact size of $\mathbf{26 mm\times 32 mm \times 0.762 mm}$ , including the feeding mechanism. Proposed antenna, which is printed on Rogers substrate with a relative permittivity of 2.2 has been easily fabricated and has low manufacturing cost. Measured results show good agreement with the simulated results and the proposed antenna has an impedance bandwidth of 3.8-14.8 GHz for a voltage standing-wave ratio less than 2. Furthermore, good radiation patterns indicate that the proposed antenna is well suited to be integrated within various portable devices for UWB application.
10 citations
01 Apr 2018
TL;DR: In this paper, a conformal microstrip angular log-periodic meander line (ALPML) traveling wave tube (TWT) based on quartz substrate is studied.
Abstract: A conformai microstrip angular log-periodic meander line(ALPML) traveling wave tube(TWT) based on quartz substrate is studied in this paper. In order to decrease the attenuation of dielectric substrate and eliminate the charge accumulation, a conformal microstrip is adopted. Conformal microstrip remove the unnecessary dielectric substrate and remain the dielectric substrate in the microstrip metal layer below. The remained dielectric substrate is as same shaped as the metal layer. By simulation, this traveling wave tube can reach 25W power output in 32GHz, which in condition of voltage 2300V and current 0.2A. The gain and efficiency is 14dB and 5.6%, respectively. The 3dB bandwidth is 10GHz from 27.5GHz to 37.5 GHz.
24 Apr 2018
TL;DR: In this article, a new slow wave structure (SWS) of azimuthal support angular log-periodic strip line SWS is presented, which is better than microstrip SWS.
Abstract: A new slow wave structure (SWS) of azimuthal support angular log-periodic strip line SWS is presented in this paper. An attractive property of the new structure is that the ability of resistance to electron bombardment is better than microstrip SWS. Applied a single radial sheet beam with the work voltage of 5920V and the current of 0.6A, the beam-wave interaction results show that the maximum output power, gain and electron efficiency are 300.3W, 14.8dB and 8.46%, respectively, in Ka band.
01 Apr 2018
TL;DR: In this article, the dispersion characteristics and coupling impedance of the SWS are calculated, and the simulation results of beam wave interaction, the planar travelling wave tube (TWT) with SWS can give the output power of 136.3W, the electron efficiency and gain approach 5.6% and 9.6dB, respectively, at 39GHz under a single fan-shaped radial sheet beam voltage of5250V and current of 0.46A.
Abstract: The ridge loaded azimuthal supported angular log-periodic strip meander line slow wave structure (SWS) is presented in this paper. The dispersion characteristics and coupling impedance of the SWS are calculated. According to the simulation results of beam wave interaction, the planar travelling wave tube(TWT) with SWS can give the output power of 136.3W, the electron efficiency and gain approach 5.6% and 9.6dB, respectively, at 39GHz under a single fan-shaped radial sheet beam voltage of5250Vand current of 0.46A.
TL;DR: In this article, the effects of different structure parameters on transmission characteristics of the 25 periods SWS during the Ka band are discussed in detail, and the experimental results show that the output power is 11.4 W at the frequency of 32 GHz, with the electron efficiency of 3.3%.
Abstract: The microstrip angular log-periodic meander line slow wave structure (SWS) on quartz substrate with coaxial input/output coupler is studied. The effects of different structure parameters on transmission characteristics of the 25 periods SWS during Ka band are discussed in detail. The SWS with the total length of ∼6.5 mm, add coaxial input/output coupler and tapered impedance microstrip line to form an entire assembly. The testing result is accordant with that of simulation. The dispersion characteristics of the SWS were obtained to determine the work voltage. The beam-wave interaction results show that the output power is 11.4 W at the frequency of 32 GHz, with the electron efficiency of 3.3%.
TL;DR: In this paper, a double-ridge-loaded folded waveguide (DRL-FW) traveling wave tube (TWT) based on period-tapered structure is proposed and analyzed for verifying the feasibility in suppressing upper-band-edge oscillation and increasing the output power.
Abstract: A double-ridge-loaded folded waveguide (DRL-FW) travelling wave tube (TWT) based on period-tapered structure is proposed. Through analysing the dispersion characteristics of the DRL-FW slow wave structure (SWS), the physical mechanism of the band-edge oscillation is obtained. Period-tapered SWS is proposed and analysed for verifying the feasibility in suppressing upper-band-edge oscillation and increasing the output power. Then the electromagnetic characteristics and the beam-wave interaction of TWT based on the period-tapered DRL-FW SWS are investigated. The calculation results predict that it potentially could provide continuous wave power over 600W from 29 GHz to 32 GHz without upper-band-edge oscillation. The bandwidth expands from 29-31GHz to 29-32GHz and electron efficiency is increased from more than 8.3% to more than 11%, while the range of operating voltage expands from 22kV-22.5kV to 22kV-24kV. The corresponding saturated gain can reach over 36.8 dB. In addition, we have carried out experimental tests on the transmission characteristics of period-tapered DRL-FW SWS. The cold test results show that the voltage stand-wave ratio (VSWR) is below 1.8 in the range of 29-32GHz. Good transmission characteristics greatly reduce the risk of reflection wave oscillation, thus improving the stability of DRL-FW TWT.A double-ridge-loaded folded waveguide (DRL-FW) travelling wave tube (TWT) based on period-tapered structure is proposed. Through analysing the dispersion characteristics of the DRL-FW slow wave structure (SWS), the physical mechanism of the band-edge oscillation is obtained. Period-tapered SWS is proposed and analysed for verifying the feasibility in suppressing upper-band-edge oscillation and increasing the output power. Then the electromagnetic characteristics and the beam-wave interaction of TWT based on the period-tapered DRL-FW SWS are investigated. The calculation results predict that it potentially could provide continuous wave power over 600W from 29 GHz to 32 GHz without upper-band-edge oscillation. The bandwidth expands from 29-31GHz to 29-32GHz and electron efficiency is increased from more than 8.3% to more than 11%, while the range of operating voltage expands from 22kV-22.5kV to 22kV-24kV. The corresponding saturated gain can reach over 36.8 dB. In addition, we have carried out experimental...
24 Apr 2018
TL;DR: In this paper, a novel slow-wave structure (SWS) named angular log-periodic folded groove waveguide was proposed, which mainly used in traveling wave tube (TWT) for G-band.
Abstract: A novel slow-wave structure (SWS) named angular log-periodic folded groove waveguide was proposed in this paper, which mainly used in traveling wave tube (TWT) for G-band. Due to the design idea owing the combination of folded groove waveguide and log-periodic form, this new SWS possess several advantages from them. Low operation voltage and weak dispersion of electromagnetic wave are merits of them. In addition, a modified equation to calculate the phase velocity in radial direction was proposed. In the end, one angular log-periodic folded groove waveguide was designed which owing 38.8W output power at 198GHz, the gain is 18.8dB when operation voltage is set to 8080V.
TL;DR: In this article, a sine waveguide (SWG) traveling-wave tube with sheet electron beam tunnel is proposed to amplify the high-frequency terahertz wave, and the slow wave characteristics including the dispersion properties and interaction impedances have been investigated by using the eigenmode solver in the 3D electromagnetic simulation software Ansoft HFSS.
Abstract: A sine waveguide (SWG) traveling-wave tube with sheet electron beam tunnel is proposed to amplify the high-frequency terahertz wave. In this study, the slow wave characteristics including the dispersion properties and interaction impedances have been investigated by using the eigenmode solver in the 3D electromagnetic simulation software Ansoft HFSS. The truncated SWG slow wave structure possesses the relatively large average coupling impedance. The beam–wave interaction characteristics of truncated SWG with sheet electron beam tunnel are calculated by high-frequency simulation software CST. From the particle-in-cell simulation results, this beam–wave interaction circuit can produce >490 mW ranging from 0.845 to 0.855 THz with a corresponding gain over 22 dB.
TL;DR: In this article, a plan about a W-band sheet beam traveling wave tube based on a staggered double vane slow wave structure is drawn up and the dispersion characteristics, transposition characteristics of highfrequency system, sheet electron beam gun, vacuum window, periodically cusped magnetic focusing system and beam-wave interaction are analyzed by CST Microwave Studio, CST Particle Studio and HFSS.
Abstract: In this study, a complete and viable plan about a W-band sheet beam travelling wave tube based on a staggered double vane slow wave structure is drawn up. The dispersion characteristics, transposition characteristics of high-frequency system, sheet electron beam gun, vacuum window, periodically cusped magnetic focusing system and beam–wave interaction are analysed by CST Microwave Studio, CST Particle Studio and HFSS. An attenuator is used in this device to suppress oscillation. A phase velocity taper is used to increase output power. The operation voltage is 20.6 kV and the current is 80 mA. With a 10 W input power, the output power is 1100 W versus the gain is 20.41 dB at 95 GHz. The peak amplitude approaches 1200 W versus the gain approaches 20.79 dB at 99 GHz.
24 Apr 2018
TL;DR: In this paper, the results of simulation and cold test were analyzed and compared with the simulated results. And the results showed that the results were in accordance with the simulation and the cold test results.
Abstract: In this paper, vacuum window and staggered double vane slow wave structure (SDV-SWS) with vacuum window of a 220GHz staggered double vane TWT are tested and compared with the simulated results. The cold test results are analyzed and compared with the simulated one. The results of simulation and cold test show a good accordance.
01 May 2018
TL;DR: In this article, a new high-power microwave-generator based on metamaterial (MTM) slow wave structure is studied, which is formed by inserting a MTM plates loaded with 2D split ring resonators (SRRs) into a rectangular waveguide.
Abstract: A new high-power microwave-generator based on metamaterial (MTM) slow wave structure is studied. The microwave structure is formed by inserting a MTM plates loaded with 2D split ring resonators (SRRs) into a rectangular waveguide. The dispersion characteristics of the unit cell are obtained by using eigenmode simulations in the High Frequency Structure Simulator (HFSS). In addition, the transmission properties and the beam-wave interaction characteristics are simulated in the Computer Simulation Technology (CST). The simulation results indicate that the novel metallic MTM backward wave oscillator (BWO) can produce 20.05 MW output peak power and an interaction efficiency of 45.56% at the frequency of 33.157 GHz.
01 Apr 2018
TL;DR: In this paper, an equivalent circuit model for the metamaterial slow wave structure (MSWS) consisting of the empty circular waveguide filled with a complementary electric split ring resonator (CeSRR) array is proposed.
Abstract: In this paper, we set up an equivalent circuit model for the metamaterial slow wave structure (MSWS) which consists of the empty circular waveguide filled with a complementary electric split ring resonator (CeSRR) array, and we propose a method to compute the resonant frequency of irregular slot-line according to the surface current distribution of the CeSRR. And then we theoretically calculate the high-frequency characteristics of the MSWS with different parameters. By comparing the results of theoretical calculations with those of simulations, we find that the results of equivalent circuit model are in good agreement with the simulation results. This fact indicates that the equivalent circuit model can be used to calculate the resonant frequency of slot-line, the dispersion characteristics and the interaction impedance for the MSWSs.
24 Apr 2018
TL;DR: In this article, an 850 GHz staggered double-vane traveling wave tube (TWT) was designed and the high frequency characteristics and transmission characteristics of the circuit were calculated and the results indicate that the reflection coefficient is below -20 dB in the frequency range from 770 GHz to 860 GHz, which including the attenuator and ridge-loaded waveguide input/output coupler.
Abstract: An 850 GHz staggered double-vane traveling wave tube (TWT) is designed in this paper. The high- frequency characteristics and transmission characteristics of the circuit are calculated and the results indicate that the reflection coefficient is below -20 dB in the frequency range from 770 GHz to 860 GHz, which including the attenuator and ridge-loaded waveguide input/output coupler. The particle-in-cell simulation is also calculated and the results show that the tube can get over 50m W output power among a wide bandwidth with an operating voltage of 28.1 kV, input power of 2mW and beam current of 20 mA.
01 Sep 2018
TL;DR: In this paper, beam-wave interaction of ridged sine waveguide and the design of sheet beam electron optical for 0.22THz backward wave oscillator (BWO) was introduced, which could create a sheet electron beam with thickness 0.05mm and width 0.4mm at waist position.
Abstract: This paper introduces beam-wave interaction of ridged sine waveguide and the design of sheet beam electron optical for 0.22THz backward wave oscillator (BWO). The electron gun which could create a sheet electron beam with thickness 0.05mm and width 0.4mm at waist position is used. The simulation result shows that the transmission current in the tunnel with 0.09mm thick and 1.2mm width is 15mA with 100% transmission. The result of beam-wave interaction shows that the signal with 1W and 16.4GHz bandwidth could be achieved by the ridged sine waveguide BWO.
TL;DR: In this article, two types of plasma-photonic-crystal-like beam-plasma systems, namely, PVPVP and PVPV, have been simulated using the particle-in-cell method, and the simulation results show that the beam electrons can be focused without an external magnetic field, and electromagnetic (EM) radiation can be observed.
Abstract: In this study, the plasma-photonic-crystal-like beam–plasma system has been proposed. Two types of plasma-photonic-crystal-like beam–plasma systems, namely plasma-vacuum-plasma-vacuum-plasma (PVPVP) beam–plasma system and plasma-vacuum-plasma (PVP) beam–plasma system, have been simulated using the particle-in-cell method. The simulation results show that the beam electrons can be focused without an external magnetic field, and the electromagnetic (EM) radiation can be observed. For the PVPVP beam–plasma system, the EM radiation frequency is 0.9035 THz, and the electron efficiency that the beam electrons give out their energy to the EM wave is 3.06%. For the PVP beam–plasma system, the EM radiation frequency is also 0.9035 THz, but the electron efficiency can be up to 10.5%. This work can contribute to the engineering practice of the beam–plasma system.
01 Apr 2018
TL;DR: In this paper, a particle-in-cell (PIC) method was used to simulate terahertz (THz) electromagnetic radiation in beam-plasma system under different plasma distribution.
Abstract: Terahertz (THz) electromagnetic (EM) radiation in beam-plasma system under different plasma distribution has been simulated using particle-in-cell (PIC) method in this paper. The calculation results show that the electromagnetic radiation frequency under radially non-uniform plasma distribution is lower than that under uniform plasma distribution, which is good agreement with the theoretical analysis. The related physical analysis about the simulation results is given out. This work will give a better physical understanding of beam-plasma system and provide guidance to the project practice
01 Apr 2018
TL;DR: In this article, a dangling slot-line Slow-Wave Structure (DSL-SWS) has been proposed and studied and the high frequency characteristics of them, including dispersion properties, and coupling impedances, have been investigated.
Abstract: A novel dangling slot-line Slow-Wave Structure (DSL-SWS) has been proposed and studied. The high frequency characteristics of them, including dispersion properties, and coupling impedances, have been investigated, which shows the DSL-SWS is broadband and the dangling slot-line traveling-wave tube (DSL-TWT) has a low voltage. The transmission structure has been designed and simulated, the reflection coefficient is less than -15dB over the frequency range from 28-39 GHz. The stimulation result predicts that the DSL-SWS is a potential choice of the Miniaturization low voltage Traveling Wave Tube (TWT) and Backward Wave Oscillator.
01 Sep 2018
TL;DR: In this paper, a Q-band sheet beam slot-line backward wave oscillator (SWO) was reported, which is much more suitable to be designed as a BWO than a traveling wave tube (TWT).
Abstract: This paper reported a Q-band sheet beam slot-line backward wave oscillator (BWO). The characteristics of slot-line slow wave structure (SL-SWS) has been investigated and the result shows that it's much more suitable to be designed as a BWO than a traveling wave tube (TWT). The slot-line backward wave oscillator is driven by a 0.19A sheet beam whose rectangular cross section is 0.9mm*0.12mm. While the beam voltage ranges from 6000V to 10000V, the frequency of output signal varies from 40.275GHz to 43.925GHz, and the output power is over 40W.
TL;DR: In this article, an experiment on Ka-band amplifiers injected and damaged by electromagnetic waves was conducted and the results showed that the uncharged amplifiers need more injected power to be damaged compared with the charged amplifiers.
Abstract: Research on amplifiers injected by high-power microwave is important and lays foundation for reinforce technology. This study reports an experiment on Ka-band amplifiers injected and damaged by electromagnetic waves. The continuous wave and the pulse wave are injected into the amplifiers which are based on HMMC5040 chips. The injected power level increases until the amplifiers are damaged. The results are recorded and analysed. The results show that: (i) the uncharged amplifiers need more injected power to be damaged compared with the charged amplifiers. (ii) To degrade or damage the amplifiers, the pulse wave need more power. (iii) The first node of the HMMC5040 chip is damaged in the experiment, so this is the key part for anti-radiation design.
01 Apr 2018
TL;DR: In this article, a uniform permanent magnetic field with hemi-ladder structure for sheet electron beam focusing is designed, which has the convenience of design and realization compared with PPM system.
Abstract: There are some sophisticated solutions for focusing sheet electron beam, such as periodic cusped magnetic focusing and periodic permanent-magnet (PPM) focusing. However, the precision of processing and assembling of the magnetic system is getting higher as magnetic blocks become thinner. Here, a uniform permanent magnetic field with hemi-ladder structure for sheet electron beam focusing is designed in this paper. The simulation result shows that a uniform magnetic field with 0.7 T can be obtained among a length of 65mm. Based on these, the designed magnetic field is applied to the focusing of a 0.3*0.08mm sheet beam with electron current of 44 mA and voltage of 22.1 kV produced by a 340GHz sheet beam electron gun, and the beam transmission efficiency measured by current is 94.34% in a 0.35*0.W*65mm drift tube. This structure has the convenience of design and realization compared with PPM system.
TL;DR: In this paper, phase-velocity-taper was used for the improvement of the beamforming of the traveling wave tube (TWT) in the frequency range from 330 to 345 GHz.
Abstract: Staggered double-vane slow wave structure as the core part of the travelling wave tube (TWT) has been more popular in recent years. However, the electron efficiency of this structure is not enough high for higher frequency, especially THz. In this study, phase-velocity-taper method is utilised for the improvement of TWT's efficiency at 340 GHz. The reflection and transmission coefficients of the whole tube with attenuator show good propagation characteristics over the wide frequency range from 330 to 345 GHz. The particle-in-cell simulation results indicate that the output power can increase about 32% at 340 GHz with respect to that of the without-taper structure. The corresponding electron efficiency is improved from 2.8 to 3.5% by phase-velocity-taper. However, the simulation results also show that the tube can produce over 30 W output power in the frequency range from 330 to 343 GHz with an operating voltage of 21.3 kV, a current of 0.043 A, and an input power of 10 mW. In addition, a sheet beam electron gun with a beam current of 43 mA, a beam voltage of 21.3 kV, and beam waist cross-sectional dimension of 0.3 mm × 0.08 mm is also designed as the particle source of the sheet-beam TWT.