115 results on '"Cui, Wanzhao"'
Search Results
2. Effective improvement of the micro-discharge threshold and environmental stability in microwave devices based on carbon/silver/titanium composite films.
- Author
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Zhao, Yanan, Zhou, Zicong, Meng, Xiangzhao, Han, Lin, Yao, Yufei, Zhu, Shukai, Cui, Wanzhao, Peng, Bin, Hu, Zhongqiang, and Liu, Ming
- Subjects
TITANIUM composites ,MICROWAVE devices ,SECONDARY electron emission ,WAVEGUIDE filters ,SILVER ,DOPING agents (Chemistry) ,ELECTRON emission ,ELECTRON field emission - Abstract
The micro-discharge effect limits the development of high-frequency microwave power components to miniaturization and integration. Therefore, it has become a focus of research to effectively suppress the micro-discharge effect, increase the micro-discharge threshold, and strengthen the environmental stability of high-frequency microwave devices. In this study, different elemental ratios of carbon (C)/silver (Ag)/titanium (Ti) composite films were obtained by multi-target magnetron co-sputtering technology and then systematically analyzed for micro-discharge effects. When the doping ratio of C/Ag/Ti was 3.538/1/0.013, the corresponding maximum secondary electron emission coefficient (δ
max ) decreased to 1.01 owing to the suppression of secondary electron emission by the increase in the content of sp2 hybrid bond. The micro-discharge threshold of Ku band waveguide filters coated with moderate C/Ag/Ti composite films showed an optimal performance of 10 000−12 500 W, which was increased by approximately 20 times. Moreover, the microstructure of the composite films exhibited higher density and flatness with a tiny increase in the titanium doping ratio, representing good environmental stability. Thus, the effective suppression of the secondary electron emission yield, significant improvement in the micro-discharge threshold, and enhancement of the environment stability of microwave components could be realized simultaneously by reasonably controlling the content of titanium in silver and titanium co-doped carbon-based composite films. [ABSTRACT FROM AUTHOR]- Published
- 2024
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3. Controllable preparation of silver nano-bowl coatings for suppressing secondary electron emission
- Author
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Ma, Jianzhong, Wei, Linfeng, Bai, Yuanrui, Bao, Yan, Kang, Qiaoling, Zhang, Wenbo, Cui, Wanzhao, Hu, Tiancun, and Wu, Duoduo
- Published
- 2021
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4. Domain Decomposition Hybrid Implicit–Explicit Algorithm with Higher-Order Perfectly Matched Layer Formulation for Electrical Performance Evaluation under Low-Pressure Discharge Phenomenon.
- Author
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Wang, Rui, Cui, Wanzhao, Zhang, Le, Wang, Yuming, and Wei, Huan
- Subjects
DOMAIN decomposition methods ,ALGORITHMS ,ORBITS (Astronomy) - Abstract
Low-pressure discharge events have a major impact on a satellite's electrical performance. Most notably, a number of serious issues arise from the inability to directly modify satellite systems that operate in orbit. Accurate analysis of electrical performance is crucial for mitigating the issues arising from the low-pressure discharge phenomenon. Complex structures, such as intricate features and curved structures, are frequently used in satellite systems' enormous microwave components. In this case, the finite-difference time-domain (FDTD) approach proposes the hybrid implicit–explicit (HIE) algorithm with a domain decomposition method to effectively simulate complex structures under the low-pressure discharge phenomenon. The bilinear transform method is adjusted in accordance with the implicit equations for the anisotropic magnetized plasma environment caused by the discharge. To end unbounded lattices, a higher-order perfectly matched layer is used at the boundary. An example of a microwave connector structure is used to show how well the algorithm performs electrically. According to the findings, the suggested algorithm behaves in a way that is consistent with both the traditional algorithm and the experiments. Furthermore, the phenomenon of low-pressure discharge has a notable impact on the electrical performance of microwave components. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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5. Design and Implementation of C-Band Large-Power Planar Butler Matrix in SRS.
- Author
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Li, Jinfeng, Yan, Liping, Liu, Changjun, Bai, He, and Cui, Wanzhao
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TRANSMITTING antennas ,REFLECTANCE ,INSERTION loss (Telecommunication) ,COAXIAL cables ,ANTENNA arrays ,MATRICES (Mathematics) - Abstract
In satellite remote sensing (SRS), there is a demand for large-power microwave components. A Butler matrix is essential to a transmitting antenna array in SRS. This article illustrates the electrical and mechanical design, simulation, and test results of a large-power planar beamforming network for SRS at C-band. It is a 4 × 4 Butler matrix based on square coaxial lines. Short-ended stubs are used in the Butler matrix to broaden its bandwidth by 10%, support inner conductors, and enhance heat transfer in vacuum environments. The simulation results are consistent with the measured results. The reflection coefficient is less than −18 dB, and the isolation is more than 23 dB from 3.8 GHz to 4.2 GHz. The insertion losses are less than 0.6 dB, and the phase errors are better than ±6°. The measured peak microwave power of the proposed Butler matrix is 9 kW. Its size is 440 × 400 × 40 mm
3 . The proposed Butler matrix beamforming network can be applied to SRS systems. [ABSTRACT FROM AUTHOR]- Published
- 2024
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6. Surface roughness evolution induced low secondary electron yield in carbon coated Ag/Al substrates for space microwave devices
- Author
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Lu, Qi, Yu, Bin, Hu, Zhongqiang, He, Yun, Hu, Tiancun, Zhao, Yanan, Wang, Zhiguang, Zhou, Ziyao, Cui, Wanzhao, and Liu, Ming
- Published
- 2020
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7. A G-Band 2-Pixel Heterodyne Receiver with Integrated Local Oscillator Chain
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Chen, Zhenhua, Chen, Xiang, Cui, Wanzhao, Li, Xiaojun, and Ge, Junxiang
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- 2019
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8. Significantly reduced secondary electron emission from silver/carbon composite films for microwave devices.
- Author
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Zhao, Yanan, Sun, Xuan, Hu, Tiancun, Bai, He, He, Yun, Yang, Jing, Cui, Wanzhao, Hu, Zhongqiang, and Liu, Ming
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SECONDARY electron emission ,MICROWAVE devices ,CARBON films ,ELECTRON emission ,HYBRID securities ,MAGNETRON sputtering ,CARBON composites - Abstract
The micro-discharge effect is a failure mechanism that often appeared in space microwave devices under vacuum conditions, such as RF (radio frequency) cavity, RF satellite missile, and antenna launching communication system. How to control micro-discharge effectively and simply has become a research hotspot. In this paper, we have prepared a series of doping silver (Ag)/carbon (C) composite films by double target magnetron sputtering technology and have significantly reduced the maximum secondary electron emission coefficient (δ
max ) from 2.522 to 1.04 when the doping ratio of Ag/C is 1.345. Theoretically, the continuous increase of sp2 hybrid bond content tuned by the existing Ag nanoparticles has a greater contribution to the conductivity and inhibition of secondary electron emission in the Ag/C composite films. Meanwhile, the gradually emerged "multi-trap" surface structure with the increase of Ag doping content has further increased the collision between excited secondary electrons and free electrons, achieving an obvious inhibition effect. The results demonstrate that secondary electron emission can be suppressed effectively by tuning the structural feature of two kinds of compounded materials with low δmax . It is of great significance in physical mechanism analysis and design of the new doping process. [ABSTRACT FROM AUTHOR]- Published
- 2022
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9. Modeling the saturation of the multipactor effect in a dielectric-loaded parallel-plate waveguide.
- Author
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Zhai, Yonggui, Wang, Hongguang, Cao, Meng, Weng, Ming, Lin, Shu, Peng, Min, Chen, Kun, Wang, Rui, Li, Yun, Cui, Wanzhao, Chen, Jun, and Li, Yongdong
- Subjects
PARALLEL-plate waveguides ,SPACE charge ,DIELECTRIC waveguides ,DIELECTRIC materials ,ELECTROSTATIC fields ,PHENOMENOLOGICAL theory (Physics) ,DIELECTRIC properties - Abstract
The aim of this paper is to establish a numerical simulation model for the multipactor effect in a partially dielectric-loaded parallel-plate waveguide, with a focus on the investigation of multipactor saturation mechanisms for different dielectric materials with different secondary emission yield (SEY) properties. An electrostatic method involving the radio-frequency fields, space charge fields, and the dynamics of charge accumulation on the dielectric surface and solutions for electrostatic fields are proposed. The evolution of the electron number, accumulated charge, and secondary electron multiplication rate for different input voltages and SEY properties of the dielectric materials are studied using numerical calculations. The results show that two physical multipactor phenomena occur in a dielectric-loaded parallel-plate waveguide: a self-sustaining phenomenon, which means that the electron population reaches a saturation level, and a self-extinguishing phenomenon. The latter can be divided into two cases: in one, the number of electrons undergoes a process of multiplication, saturation, and reduction, and in the other, the number of electrons disappears after their population reaches a maximum. Furthermore, a multipactor susceptibility diagram for SEY curves of different dielectric materials is constructed. The results show that the multipactor effect is suppressed when the maximum of the SEY curve is less than 1.3. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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10. Quantitative domain evaluation in rhombohedral BS-PT piezoelectric ceramics via diffraction-plane-transformation model.
- Author
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Wu, Jingen, Wu, Chaoyu, Qiao, Jiacheng, Xu, Yiwei, Du, Yongjun, Wang, Zhiguang, Bai, He, Cui, Wanzhao, Hu, Zhongqiang, and Liu, Ming
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FERROELECTRIC materials ,CRYSTAL structure ,MODEL airplanes ,PIEZOELECTRIC ceramics ,CERAMICS - Abstract
The domain structure fundamentally determines the piezoelectric/ferroelectric performance of ferroelectric materials. To understand the correlation between macro-properties and microstructure, the evolution of domain structure should be clearly figured out. Here, the diffraction-plane-transformation (DPT) model is proposed for the domain evaluation in BS-PT piezoelectric ceramics of rhombohedral crystalline structure. The transformation between different crystal planes is accurately revealed by the DPT model. Then, non-180° domain reversal in rhombohedral 0.4BiScO
3 –0.6PbTiO3 piezoelectric ceramics (abbreviated as BS-PT) can be quantitatively estimated, whether in electric poling or thermal depoling processes. Experimentally, the correlations between piezoelectric coefficients, electromechanical coupling properties, and non-180° domain reversal percentage are investigated. It is proven that the DPT model provides an effective method for the non-180° domain estimation in rhombohedral crystalline ceramics. [ABSTRACT FROM AUTHOR]- Published
- 2023
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11. A High-Power G-band Schottky Local Oscillator Chain for Submillimeter Wave Heterodyne Detection
- Author
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Chen, Zhenhua, Chen, Xiang, Cui, Wanzhao, Li, Xiaojun, and Ge, Junxiang
- Published
- 2015
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12. The total secondary electron yield of a conductive random rough surface.
- Author
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Ye, Ming, Feng, Peng, Wang, Dan, He, Yongning, Li, Yun, and Cui, Wanzhao
- Subjects
THREE-dimensional printing ,SURFACE roughness ,ELECTRIC propulsion ,ELECTRON emission ,NANOSTRUCTURED materials ,CARBON fibers ,ELECTRON scattering - Abstract
One problem with current 3D printed microwave components is that they usually have more surface roughness than components manufactured with traditional machining processes. To estimate the multipactor threshold of 3D printed microwave components, it is important to evaluate the total secondary electron yield (TSEY) of the random rough surface. In this work, taking copper as an example, we conduct TSEY simulations for random rough surfaces. First, we generate both isotropic and anisotropic Gaussian type random rough surfaces; then, the dependence of the TSEY on both the roughness and correlation length is studied using Monte-Carlo simulations. Results show that when the root-mean-square roughness increases from 0 to 30 μm, the maximum TSEY increases slowly at first and then decreases rapidly. In other words, roughness can also enhance and not just suppress the TSEY. The results can be interpreted as follows: for a relatively smooth/rough surface, the TSEY enhancement/suppression induced by oblique incidence/a shadowing effect plays a dominant role. Simulation results also show that correlation length has a notable effect on the TSEY. Furthermore, for anisotropic surfaces, the azimuthal angle also influences the TSEY. Compared with currently published work, we provide an optional evaluation method for the TSEY of random rough surfaces. The predictions in this work not only confirm existing observations (the TSEY suppression effect) but also present new predictions (the TSEY enhancement effect and the azimuthal angle effect). [ABSTRACT FROM AUTHOR]
- Published
- 2019
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13. Secondary electron emission characteristics of TiN coatings produced by RF magnetron sputtering.
- Author
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Wang, Dan, He, Yongning, and Cui, Wanzhao
- Subjects
TITANIUM nitride ,SURFACE coatings ,MAGNETRON sputtering ,ELECTRON emission ,NANOSTRUCTURED materials ,ELECTRICAL resistivity ,SEMICONDUCTORS ,ELECTRON traps - Abstract
Multipactor, a frequent detrimental effect in space high power systems, can degrade the performance of space microwave components or even cause devastation. Surface coatings with a low secondary electron yield (SEY) have been verified to mitigate multipactor efficiently, and some literature indicates that titanium nitride (TiN) coating is an excellent multipactor suppressor due to its recognized low SEY, whereas so far, the theoretical analysis for interpreting secondary electron emission (SEE) characteristics of TiN coatings is scarce. In this work, we experimentally and theoretically investigate the SEE characteristics of TiN coatings. We fabricate seven TiN coatings at different N
2 concentrations by RF sputtering. The microscopic analysis indicates that the nanostructured TiN coatings are more likely to be formed at low N2 concentration, inversely, the compact TiN films are more likely to be formed at high N2 concentration. The SEE measurement shows that the nanostructured TiN coatings are more efficient to trap electrons than the compact TiN films do. Furthermore, via measuring resistivity, we find a novel regularity that the variation in true SEY largely depends on the resistivity for compact TiN films. Namely, the true SEY of compact TiN films linearly decreases as their resistivity exponentially declines. Then, we establish an equation to describe the true SEY as a function of resistivity via applying the semiconductor conductivity theory to Dionne's SEE model. The equation qualitatively interprets the experimental regularity. This work presents a probability to control the SEE level of TiN coatings by adjusting resistivity and is of significance to comprehend the SEE of semiconductors. [ABSTRACT FROM AUTHOR]- Published
- 2018
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14. Testing of Passive Intermodulation Based on an Ultrawideband Dual-Carrier Nulling.
- Author
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Zhu, Chengkai, Chen, Zhenyu, Zhang, Bin, Wang, Xinbo, Cui, Wanzhao, Li, Yun, Zhu, Zhongbo, Li, Xiaojun, Wang, Jun, Wu, Song, and Ran, Lixin
- Subjects
INTERMODULATION ,RADIO frequency ,MICROWAVE communication systems ,BASEBAND ,PROBLEM solving ,MICROWAVE devices - Abstract
The occurrence of passive intermodulation (PIM) is inevitable in high-power microwave devices. It interferes with wireless communication and radar systems, resulting in severe deterioration of receiving performance. So far, narrowband PIM analyzers have been realized for different business bands. However, they are incapable of testing wideband systems. To solve this problem, rack-mounted analyzers piled with multiple narrowband analyzers were implemented. While such solutions significantly increase the volume, cost, and power consumption, they cannot provide a wide, continuous bandwidth for PIM localizations. Aiming to solve this problem, we propose a novel solution for realizing ultrawideband PIM analyzers. Based on the principle of cooperative radio frequency and baseband (RF-BB) nulling, we demonstrate an experimental prototype working within a continuous frequency band covering three octaves, exhibiting promising potential in PIM testing applications. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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15. Multiaperture multibeam antenna design method for high‐throughput satellite applications.
- Author
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Tao, Xiao, Ding, Wei, Zhang, Xingang, Ye, Wenxi, Cui, Wanzhao, Deng, Heng, and Zhang, Ke
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ANTENNA design ,APERTURE antennas ,TELECOMMUNICATION satellites ,RECEIVING antennas ,STRUCTURAL design ,NANOSATELLITES ,MATHEMATICAL optimization ,ANTENNAS (Electronics) - Abstract
As the core technology of high‐throughput satellite payloads, multibeam antennas have received high attention and rapid development in recent years. Because of the characteristics of high gain and high beam isolation, multiaperture multibeam antennas is an important technical approach to meet the high‐performance requirements of high‐throughput satellites. This article proposes a mathematical modeling method based on the mutual coupling parameters of the reflector. This method takes capacity requirements and satellite structure design boundary conditions as input condition, and adopts an adaptive evolutionary multiobjective optimization algorithm to perform joint optimization and solution of multiple parameters, which can complete the optimization efficiently. This method does not need to perform a large number of antenna parameter simulation, reduces the number of iterations and structural layout design, greatly reduces the design cost. This article takes the demand of the AP‐6D satellite as an example, applies the above method to the multibeam antenna design of the satellite, and completes the simulation verification, structural design, physical manufacturing, and various tests of the antenna to verify the correctness of the design method. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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16. Design of Pattern Reconfigurable Patch Antenna Array Based on Reflective Phase-Shifter.
- Author
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Shang, Yuqiu, Zeng, Qingsheng, Cui, Wanzhao, Wang, Xinwei, and Zheng, Gengqi
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ANTENNA arrays ,MICROSTRIP antenna arrays ,PHASE shifters ,DIRECTIONAL couplers ,VARACTORS ,DIRECTIONAL antennas - Abstract
A circularly polarized (CP) broadside antenna array with a continuously adjustable beam is proposed and implemented. First, a reflection phase shifter with varactor diodes loaded on two output terminals of a branch directional coupler is realized. By controlling the voltage across both ends of the varactor diodes in the terminal load circuit, the reactance of the load is changed, allowing control of port phase shift. Following that, the microstrip patch antenna array is combined with the reflection phase shifter to achieve the pattern reconstruction for the array. For verification, a prototype of the designed pattern reconfigurable antenna (PRA) is fabricated and measured. The measurement results indicate that the beam direction of the antenna can be continuously adjusted with a change in the voltage across the varactor diodes. The maximum beam direction of the antenna reaches ±21° when the biggest DC bias voltage across the varactor diode is chosen as 15 V. Besides, the antenna shows good CP performance in different beam directions. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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17. Voltage Control of Perpendicular Exchange Bias in Multiferroic Heterostructures
- Author
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Yang, Qu, Hu, Zhongqiang, Zhang, Yao, Su, Wei, Peng, Bin, Wu, Jingen, Zhou, Ziyao, He, Yun, Cui, Wanzhao, Wang, Zhiguang, and Liu, Ming
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Condensed Matter::Materials Science ,Condensed Matter - Materials Science ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences - Abstract
Perpendicular exchange bias (EB), which combines the perpendicular magnetic anisotropy and the ferromagnetic (FM) - antiferromagnetic (AFM) exchange coupling, is extremely important in the high-density AFM spintronics. However, the effective modulation of EB remains challenging, since the alternant spins at the AFM/FM interface are strongly pinned by the AFM layer. Voltage tuning of EB through the magnetoelectric coupling provides a potential way to achieve a rapid magnetization switching in an energy-efficient manner. Nevertheless, the interfacial strain mediation of perpendicular EB induced by E-field remains unexplored. In this work, we obtain perpendicular EB nanostructure by room-temperature fabrication process, and demonstrate the voltage tunable perpendicular EB in Pt/IrMn/(Co/Pt)2/Ta/(011) Pb(Mg1/3Nb2/3)O3-PbTiO3 multiferroic heterostructure. To enhance the voltage control effect on perpendicular EB, we further investigate both strain-mediated magnetoelectric coupling and ionic liquid gating method in the thinned EB system with the structure of Pt/IrMn/Co/Pt/Ta. As a result, the voltage induced lattice distortion effectively transmits to the AFM/FM interface, while the charge accumulation in gating method generates a relatively large hysteresis loop offset that has not been observed before at room temperature. The voltage manipulation of perpendicular EB at room temperature provides new possibilities towards novel AFM devices and memories with great energy-efficiency and ultra-high density., 21 pages, 6 figures
- Published
- 2019
18. Hard–Soft Groove Gap Waveguide Based on Perpendicularly Stacked Corrugated Metal Plates.
- Author
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Sun, Dongquan, Chen, Xiang, Guo, Li-Xin, Cui, Wanzhao, and Deng, Jing-Ya
- Subjects
BAND gaps ,METALS ,SUBSTRATE integrated waveguides - Abstract
A new electromagnetic band gap (EBG) structure based on the soft and hard surfaces for gap waveguide (GW) technology is introduced in this article. The proposed EBG structure consists of a soft surface and a hard surface in parallel with a gap between them, where the ridges/corrugations of the two surfaces are perpendicular to each other or with an angle near 90°. Compared with the contactless bed of nails EBG, the most widely used EBG structure in GW technology, the structural strength of the new EBG structure is increased significantly, which makes it very suited for high-frequency applications. Another advantage is that with the varying of the angle between the ridges/corrugations of the two surfaces, the stopband shifts in a wide frequency band, which makes the stopband tunable after the EBG is fabricated. The stopband performance of the proposed EBG is investigated. Straight and bended groove GWs (GGW) employing this new EBG are designed, manufactured and tested. The isolation performance with different columns of ridges/corrugations is also tested. The measured results show the proposed GGWs have excellent transmission performance. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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19. Characteristics of secondary electron emission and multipactor from a nested microtrap structure surface.
- Author
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Liu, Lu, Feng, Guobao, Chen, Bangdao, Wang, Ning, and Cui, Wanzhao
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MONTE Carlo method ,SECONDARY electron emission ,SURFACE structure ,ELECTRON emission ,ELECTRON traps ,PLASMA sheaths ,PLASMA etching ,ROUGH surfaces ,ELECTRON field emission - Abstract
It is known that an appropriate surface structure can suppress the secondary electron emission as a result of the receded multipactor in a spacecraft microwave component. On the other hand, the multiplier effect caused by electron re-entrance in ordinary surface structures can degrade the suppression of secondary electron emission. The present paper concerns our proposition of a new type of two-level nested microtrap structure surface able to effectively inhibit the generation of the secondary electrons inside the trap structure to achieve better suppression of the total secondary electron emission on the surface. The surface of a two-level nested microtrap array structure was obtained by lithography, stripping, dry etching, and Ag sputtering. Experimental tests were conducted on the two proposed nested structures with different sizes. The test results show that inhibition effects of the two structures have been improved by 100% and 144% compared with those of the traditional single-hole trap structure. The secondary electron yield on the bottom surface of the rough nested trap due to Ag sputtering is higher than that of the ideal regular structure simulated by Monte Carlo. In addition, the larger depth-to-width ratio of the nested trap can inhibit the multi-generation multiplication of electrons in the trap more effectively and further improve the inhibition effect on secondary electrons. For an impedance transformer, the proposed two size nested structure surface can increase the multipactor power threshold by about 346% and 386%. This method plus the nested microtrap structure can achieve a better secondary electron emission suppression effect and further improve the multipactor threshold of space microwave components. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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20. A Combined Susceptibility Diagram Including the Average Secondary Emission Yield on the Dielectric Surface.
- Author
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Zhai, Yonggui, Wang, Hongguang, Li, Yongdong, Cao, Meng, Lin, Shu, Weng, Ming, Li, Yun, Cui, Wanzhao, and Chen, Jun
- Abstract
This letter proposed a combined susceptibility diagram, applicable to investigating and differentiating the inherent mechanism of multipactor in dielectric-loaded microwave devices. This susceptibility diagram consists of average secondary emission yield on the dielectric surface and both the surfaces. Using this diagram, we predict the electron multiplication mechanism in the partially dielectric-loaded parallel-plate waveguide. It is found that the multipactor extinguishing only occurs for a low multipaction rate, while the saturation occurs for a higher multipaction rate. To verify its validity, the dynamic evolution of multipactor is investigated by electrostatic particle-in-cell. A good agreement between simulations and prediction results has been achieved. This susceptibility diagram thus constructed can provide a guidance to clearly identify the condition for multipactor extinguishing or saturation. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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21. Transient Analysis of High-Power Microwave Air Breakdown under External DC Magnetic Field.
- Author
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Wang, Lin, Ding, Dazhi, Chen, Rushan, Cui, Wanzhao, and Wang, Rui
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MAGNETIC fields ,MAXWELL equations ,TRANSIENT analysis ,MICROWAVES ,GALERKIN methods - Abstract
This article concentrates on the high-power microwave (HPM) breakdown process and behaviors in air-filled rectangular waveguide under the external dc magnetic field. To solve the persuasive issue, a three-dimensional (3-D) multiphysics model coupling full-wave Maxwell’s equations with plasma fluid equations is established and solved by the spectral-element time-domain (SETD) method. In our simulation, the Galerkin’s method is employed for the space discretization and the central difference scheme is used for the temporal discretization during the SETD process. The numerical results reveal that the external dc magnetic field applied in breakdown volume can significantly enhance the breakdown threshold to suppress the HPM breakdown, which is beneficial for the propagation of HPM pulse in air-filled waveguide. Our research provides theoretical guidance for suppressing the impact of HPM breakdown for HPM devices protection. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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22. A theoretical model for suppression effect of single-surface multipactor on dielectric by external DC magnetic field.
- Author
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Sun, Yanzi, Zhang, Ziyi, Liu, Zhen, Cui, Wanzhao, and Chang, Chao
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MAGNETIC fields ,ELECTRIC fields ,DIELECTRICS ,TANGENTIAL force ,RADIO frequency ,DIRECT currents - Abstract
This paper proposes a theoretical model for the single-surface multipactor on a dielectric. We consider the combined effects of the normal cumulative electric field, the normal and tangential radio frequency (RF) electric fields, as well as the tangential external direct current (DC) magnetic field and study the suppression effect of the tangential external DC magnetic field on the resonant multipactor. Kinetic properties of the electron and the resonant multipactor condition with no tangential external DC magnetic field are derived by analytical calculations. The flight time of the electron is analyzed profoundly by considering different values of the electron's initial energy, the amplitude ratio between the normal cumulative electric field and the normal RF electric field, and the tangential external DC magnetic field. Our results demonstrate that the tangential external DC magnetic field can decrease the flight time, and hence, the resonant multipactor can be suppressed or mitigated effectively by the tangential external DC magnetic field. The flight time of the electron shows a decreasing trend as the electron's initial energy increases, and the amplitude ratio between the normal cumulative electric field and the normal RF electric field decreases. The suppression effect of the tangential external DC magnetic field on the resonant multipactor can be much stronger when the amplitude ratio between the normal cumulative electric field and the normal RF electric field becomes larger. The resonant multipactor suppressing is also relevant to the amplitude ratio and the initial phase difference between the tangential and normal RF electric fields. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
23. Electron beam irradiation on novel coronavirus (COVID-19): A Monte–Carlo simulation.
- Author
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Feng, Guobao, Liu, Lu, Cui, Wanzhao, and Wang, Fang
- Subjects
SARS-CoV-2 ,COVID-19 ,ELECTRON beams ,ELECTRON impact ionization ,MONTE Carlo method ,IRRADIATION - Abstract
The novel coronavirus pneumonia triggered by COVID-19 is now raging the whole world. As a rapid and reliable killing COVID-19 method in industry, electron beam irradiation can interact with virus molecules and destroy their activity. With the unexpected appearance and quickly spreading of the virus, it is urgently necessary to figure out the mechanism of electron beam irradiation on COVID-19. In this study, we establish a virus structure and molecule model based on the detected gene sequence of Wuhan patient, and calculate irradiated electron interaction with virus atoms via a Monte Carlo simulation that track each elastic and inelastic collision of all electrons. The characteristics of irradiation damage on COVID-19, atoms' ionizations and electron energy losses are calculated and analyzed with regions. We simulate the different situations of incident electron energy for evaluating the influence of incident energy on virus damage. It is found that under the major protecting of an envelope protein layer, the inner RNA suffers the minimal damage. The damage for a ∼100-nm-diameter virus molecule is not always enhanced by irradiation energy monotonicity, for COVID-19, the irradiation electron energy of the strongest energy loss damage is 2 keV. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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24. Nonstationary Statistical Theory for Single-Surface Dielectric Multipactors.
- Author
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Shen, Fazhong, Wang, Xinbo, Cui, Wanzhao, and Ran, Lixin
- Subjects
POLARITONS ,FLUCTUATIONS (Physics) ,DIELECTRICS ,SECONDARY electron emission ,ZENITH distance ,RANDOM variables ,MONTE Carlo method - Abstract
The analytical description of dielectric multipactors requires an accurate physical model. In this article, a nonstationary statistical theory for the analysis of single-surface dielectric multipactors is established by defining an emission-to-emission transition rate and involving all the probability densities related to the emitted secondary electrons. Under the same conditions, the fluctuation of electrons in the evolution process of dielectric multipactors was calculated by the proposed theory and simulated by a commercial particle simulation tool developed based on the Monte Carlo analysis. The calculated results comply well with the simulated ones. Our results also indicated that to obtain an adequate accuracy, at least two random variables, the emission velocity and zenith angle, need to be considered. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
25. Simulation studies of interface dynamics of secondary electron yield in perforated media.
- Author
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Li, Yun, Ye, Ming, Yang, Jing, He, Yongning, Cui, Wanzhao, and Wang, Dan
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POLARITONS ,INTERFACE dynamics ,MONTE Carlo method ,POROUS metals ,ELECTRONS ,METALLIC surfaces - Abstract
The Secondary Electron Yield (SEY) is one of the key factors of multipactor, which remains a serious potential risk for high power vacuum applications. In this paper, the SEY and electron dynamics at different porous medium interfaces have been analyzed numerically for multipactor simulation and suppression. Due to the existence of an RF field, accumulated charge field, and external bias magnetic field, the previous electron trajectory tracking method in porous metal surfaces is not applicable. The real electromagnetic field distributions in porous medium, including metal and dielectric, are obtained theoretically and numerically for the calculation of electron motion. Based on the Monte Carlo simulation method, a novel numerical algorithm is proposed for the SEY calculation in porous medium. Simulation results show that SEYs of the porous dielectric perforated with cylindrical pores are correctly calculated and match well with experiments. It is demonstrated that the SEY at the porous interface is not only determined by electron motions but is also affected by the geometry structures of micro-pores. Different from the metal surface, the SEY at the porous dielectric interface increases when the width-to-depth ratio of micro-pores is greater than 1. The SEY reduces only since the depth of micro-pores is larger than lateral dimensions. As the depth gets much larger than the width, the "electron trapping" effect becomes remarkable and the SEY reduces considerably, which is promising for multipactor-free design in high power applications. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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- View/download PDF
26. An Analytical Model of One-Sided Multipactor on a Dielectric of a Metal Surface for Spacecraft Application.
- Author
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Zhang, Ziyi, Sun, Yanzi, Cui, Wanzhao, Zhang, Hongtai, Huang, Yindong, and Chang, Chao
- Subjects
METALLIC surfaces ,DIELECTRICS ,ELECTRON emission ,ELECTRIC fields ,RADIO frequency - Abstract
The aim of this article is to establish a general and practical analytical model of the one-sided multipactor on a dielectric of a metal surface and analyze the resonant multipactor effect for the recent growing interest in spacecrafts. A theoretical multipactor model involving a normal static electric field, a radio frequency (RF) electric field with both tangential and normal components, and the influence of the desorption gas is proposed. The kinetic properties and the resonant condition of the electron are studied by analytical calculations. The results show that the transit time of the electron decreases with the increase in the normal static electric field and the pressure of the desorption gas. The emission phase of the electron is the paramount factor that has a direct influence on the occurrence of the resonant multipactor. If the resonant multipactor effect could appear, the emission phase of the electron should be larger than a critical phase, and the ratio between the amplitude of the normal component of the RF electric field and the normal static electric field should be larger than a specific value as well. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
27. Transient Characteristics of Charging Effects due to E-Beam Irradiation: A Method of SEY-Based Charging Balance Mode.
- Author
-
Feng, Guobao, Liu, Lu, Cui, Wanzhao, Wang, Rui, and Hu, Tiancun
- Subjects
ELECTRON beams ,DIELECTRIC function ,IRRADIATION ,DIELECTRIC loss ,SURFACE potential ,CARRIER density - Abstract
Charging effects of dielectric due to space electron beam irradiation have a huge impact on spacecraft. To understand charging equilibrium characteristics of dielectric under electron beam irradiation, in this paper, we present a novel numerical simulation method for analyzing the secondary electron yield (SEY) based on a charging balance mode. We used the Mott scattering model and the Penn dielectric function (PDF) model to calculate the collisions between incident electrons and material the atoms of material. For internal charge transport, we considered the processes of drift, diffusion, trapping, and neutralization. These were calculated with a finite-difference time-domain (FDTD) method. Based on mechanisms of import–export dynamic charge evolution, charging balance can be categorized into three modes: SE mode, leakage (LE) mode, and cooperation (CO) mode (a combination of the two). In most situations, the SE mode corresponds to the surface charging state, while the LE mode always corresponds to deep charging states. Shortening the distance of free charge transport, a thinner sample is more likely to present as LE mode. Although the surface potential can be enhanced by monotonously increasing the thickness, the total internal charge quantity approaches a local maximum with thickness because of a charging balance mode transformation. In addition, with a larger average density of carriers in the LE mode, the material conductivity is enhanced and the dielectric loss tends to be larger at low frequencies (<103 Hz). The charging balance mode method in this study can also be appropriate to the analyses of altering irradiation parameters and materials intrinsic parameters. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
28. Gap Waveguide With Interdigital-Pin Bed of Nails for High-Frequency Applications.
- Author
-
Sun, Dongquan, Chen, Xiang, Deng, Jing-Ya, Guo, Li-Xin, Cui, Wanzhao, Yin, Kang, Chen, Zhenhua, Yao, Changfei, and Huang, Feng
- Subjects
MILLING cutters ,PLATING ,BEDS ,COPLANAR waveguides - Abstract
A new kind of contactless electromagnetic bandgap (EBG) structure in the form of interdigital-pin bed of nails is introduced for the first time in this paper. It consists of two metal plates with interdigital-pin bed of nails face to face with each other, where each pin is surrounded by four pins on the other plate. The working mechanism of the interdigital-pin contactless EBG structure is suppressing the modes supported by the parallel plate waveguide (PPW) by loading interdigital pins inside the PPW. The advantage of the interdigital-pin lattice is there is a significant pin gap increase. This lattice makes the minimum pin gap that could be processed by the machining center, after assembling, reduced from the diameter of the milling clutter to its radius. It provides a way to process EBG structures at higher frequency band with the same milling cutter. The cases the pins allocated between the two plates in a random manner are also studied. Compared to its traditional counterpart, the stopband is stable with a small variation. A W-band groove gap waveguide (GGW) prototype with interdigital-pins and a Ka-band GGW with randomly allocated pins are designed, manufactured, and tested. The measured results agree well with the simulation. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
29. All-angle Brewster effect observed on a terahertz metasurface.
- Author
-
Wang, Chun, Zhu, Zhongbo, Cui, Wanzhao, Yang, Yanbin, Ran, Lixin, and Ye, Dexin
- Subjects
INTERFACES (Physical sciences) ,POLARIZERS (Light) ,LONGITUDINAL waves ,ELECTRIC impedance ,PHASE shifters - Abstract
In physics, the Brewster effect initially refers to a reflectionless transmission of a transverse-magnetic wave that impinges on an interface separating two different regular media at a particular angle, known as the Brewster angle. Nowadays, people have recognized that the Brewster effect can also be observed under transverse-electric incidences such as in magnetic media. However, all Brewster effects observed so far were associated with a unique incident angle. In this work, we demonstrate a Terahertz metasurface on which the Brewster effect can be observed at all angles of incidence. The underlying physics behind this all-angle Brewster effect is the dispersion engineered at each angle of incidence to strictly match the longitudinal wave impedance on both sides of the surface. Theoretical analysis, full-wave simulation, and experimental results are consistent with each other. The proposed approach is simple but robust and scalable to other frequencies, implying promising applications such as perfect polarizers and space phase shifters. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
30. Experimental Verification of Multipactor Discharge Dynamics Between Ferrite Dielectric and Metal.
- Author
-
Li, Yun, Wang, Dan, Yu, Ming, He, Yongning, and Cui, Wanzhao
- Subjects
ELECTRICAL engineering ,DIELECTRIC materials ,DIELECTRIC devices ,DIELECTRIC properties ,SCANNING electron microscopy - Abstract
The underlying mechanisms of multipactor between dielectric and metal and the discharge threshold of practical dielectric components have been investigated numerically and experimentally in this paper. The reduction in secondary electron yield (SEY) and the change in surface condition are achieved using the microstructure processing technology on both of ferrite dielectric and metal. Combined with the electromagnetic particle-in-cell method, the SEY model fit with the experimental data is utilized to simulate multipactor in three groups of ferrite circulators with different surface conditions. Simulation and experimental results demonstrate that the multipactor threshold of the circulator is increased by a factor of 2 through the SEY reduction on the ferrite and is increased by a factor of more than 8, from 380 W to more than 3400 W, through the SEY reduction on both of the ferrite and the metal. Different multipactor discharge mechanisms, including two-side multipactor with positive charge accumulation, singe-side multipactor with negative charge accumulation, and multipactor suppression effect, exist in circulators with the same physical structure and different surface conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
31. Generation of Coherent Multicarrier Signals for the Measurement of Multicarrier Multipactor.
- Author
-
Wang, Xinbo, Qi, Xiaokang, Chen, Xiang, Wei, Huan, Wang, Baoxin, Guo, Luchuan, Sun, Qinfen, Cui, Wanzhao, Yin, Xinshe, Zhang, Hongtai, Zhang, Xiaoning, Li, Yongdong, Liu, Chunliang, Zhang, Bin, Ye, Dexin, and Ran, Lixin
- Subjects
RADIO frequency measurement ,PHASE-locked loops ,SIGNAL generators ,MIMO systems ,PHASED array antennas - Abstract
Many radio frequency measurement systems require multicarrier signals with coherent phases between carriers with different frequencies. A typical example is the signal generator which is used in multicarrier multipactor (MM) testing systems. In this paper, we propose a new approach for the generation of coherent multicarrier signals based on a state-of-the-art phase-locked loops technique. Different from existing systems that rely on a heavy use of commercial microwave instruments, this generator can be implemented with on-shelf chips and devices. As an example, an ultrahigh frequency band generator is implemented and how to implement the in-system calibration of this generator in an experimental multipactor testing system is demonstrated. Based on the proposed approach, performing a quantitative experimental research on MM becomes affordable for an ordinary microwave laboratory, which may promote the in-depth experimental study in this area. It can also be used in a wide range of applications such as MIMO and phased array systems. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
32. Localization of Passive Intermodulation Based on the Concept of $k$ -Space Multicarrier Signal.
- Author
-
Zhang, Mei, Zheng, Chuan, Wang, Xinbo, Chen, Xiang, Cui, Wanzhao, Li, Jun, Huangfu, Jiangtao, Ye, Dexin, Qiao, Shan, Li, Changzhi, and Ran, Lixin
- Subjects
INTERMODULATION ,PASSIVE components ,MICROWAVE devices ,MULTI-carrier modulation ,INDOOR positioning systems - Abstract
Passive intermodulation (PIM) potentially occurs in all high-power passive microwave devices. It can severely deteriorate the receiving performance of wireless communication and radar systems. To date, the simultaneous localization of multiple PIM sources in practical microwave devices is still a technical challenge. In this paper, we indicate that if a reference PIM source can be introduced into the standard PIM testing system, and the amplitude and frequency-dependent phase difference between the reference and the real PIM products can be used to construct a k-space multicarrier signal, PIM localization algorithms for both wideband and narrowband devices can be proposed based on the inverse k-space Fourier transform and inverse optimization of the partial multicarrier signal. Simulation and experimental results validate the effectiveness of the proposed approaches. These methods can solve the difficulty of multipoint PIM localization, and can be widely used in the design, production, testing, and troubleshooting of high-power microwave systems. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
33. 2D PIM Simulation Based on COMSOL
- Author
-
Wang, Xinbo, Cui, Wanzhao, Wang, Jingyu, Pan, Jingnan, Zheng, Xiaocheng, Huangfu, Jiangtao, and Ran, Lixin
- Abstract
Passive intermodulation (PIM) is a problematic type of nonlinear distortion en- countered in many communication systems. To analyze the PIM distortion resulting from ma- terial nonlinearity, a 2D PIM simulation method based on COMSOL is proposed in this paper. As an example, a rectangular waveguide ¯lled with nonlinear dielectric was taken. Both of the e®ect of nonlinear coe±cients and geometrical discontinuities were taken into consideration. The contribution of this paper is to make the PIM simulation more convenient, especially for those who are not good at analytical methods, and those who are not familiar with computational techniques. This type of analysis will aid in the development of PIM prediction, as well as PIM mitigation in the future.
- Published
- 2011
34. The secondary electron facility at China Academy of Space Technology (Xi'an).
- Author
-
Miao, Guanghui, Cui, Wanzhao, Zhang, Na, Yang, Jing, and Zhang, Heng
- Published
- 2016
- Full Text
- View/download PDF
35. Exploration of the relationship between emitted energy spectrum and multipactor threshold.
- Author
-
Zhang, Heng, Cui, Wanzhao, Li, Jun, Li, Yun, and Yang, Jing
- Published
- 2016
- Full Text
- View/download PDF
36. Monte Carlo Analysis of Occurrence Thresholds of Multicarrier Multipactors.
- Author
-
Wang, Xinbo, Shen, Jianhua, Wang, Jingyu, Song, Qingqing, Wang, Zhiyu, Li, Yun, Wang, Rui, Hu, Tiancun, Xia, Yafeng, Sun, Qinfen, Yin, Xinshe, Cui, Wanzhao, Zhang, Hongtai, Zhang, Xiaoning, Liu, Chunliang, Li, Changzhi, and Ran, Lixin
- Subjects
MICROWAVE devices ,MONTE Carlo method ,MULTI-carrier modulation ,THRESHOLD voltage measurement ,ELECTROMAGNETISM - Abstract
The newly discovered “long-term” multicarrier multipactors that can be induced by low-energy electric fields potentially threatens the reliability of spaceborne microwave systems. It also causes a new technical challenge to the prediction of the global occurrence threshold of multicarrier multipactors. In this paper, we propose efficient approaches to rapidly compute the fluctuation of space electrons in the evolving process of a multicarrier multipactor, based on which Monte Carlo approaches are developed to efficiently find the global “worst case” waveforms and the occurrence thresholds for both “single-event” and “long-term” multipactors. The proposed approaches can be used for wideband devices, providing an efficient integrated solution for the multicarrier multipactor analysis for practical high-power microwave devices with inhomogeneous field distribution. [ABSTRACT FROM PUBLISHER]
- Published
- 2017
- Full Text
- View/download PDF
37. Analytic Passive Intermodulation Model for Flange Connection Based on Metallic Contact Nonlinearity Approximation.
- Author
-
Zhao, Xiaolong, He, Yongning, Ye, Ming, Gao, Fan, Peng, Wenbo, Li, Yun, Bai, Chunjiang, and Cui, Wanzhao
- Subjects
INTERMODULATION ,CONTACT resistance (Materials science) ,ROUGH surfaces ,CURRENT density (Electromagnetism) ,MICROWAVE communication systems - Abstract
Passive intermodulation (PIM) is one of the major reliability problems in microwave communication systems. In this paper, the PIM interference generated by the metal–insulator–metal (MIM) contact nonlinearity was analytically modeled and experimentally verified. The pressure-dependent nonlinear $I$ – $V$ equations of the MIM contact were derived based on electrical contact theory and verified using a manufactured MIM contact structure. Then a point source model for the PIM product based on the metallic contact nonlinearity was proposed. The PIM product is mainly determined by the contact resistance, surface current density, and nonlinear current coefficient from the model, and in the small contact resistance region, the PIM level decreasing rates are 60, 60, and 20 dB/decade by decreasing the contact resistance, surface current density, and the nonlinear current coefficient, respectively. A designated PIM current source was utilized to verify the relationship. In the end, the PIM equation for the rectangular waveguide connection was derived based on the point source model. This model will provide guidance on low PIM system design. [ABSTRACT FROM PUBLISHER]
- Published
- 2017
- Full Text
- View/download PDF
38. A Folded Contactless Waveguide Flange for Low Passive-Intermodulation Applications.
- Author
-
Chen, Xiang, Sun, Dongquan, Cui, Wanzhao, and He, Yongning
- Abstract
Contact nonlinearity is one of the primary sources of passive intermodulation (PIM). Common methods to eliminate the contact nonlinearity are focused on improving the electrical contact. In this letter, the contactless waveguide flange (CWF) based on gap waveguide technology is first applied to solve the PIM problem caused by waveguide connection. A compact folded CWF is proposed for low-frequency applications. The artificial magnetic conductor plate, in the form of a bed of nails, is arranged surrounding the outer surface of the male flange, whereas a waveguide with broader hollow end serves as the female flange. The size of the proposed contactless flange is significantly reduced compared to its planer counterpart. An S-band prototype is designed, manufactured, and measured. Compared to traditional waveguide flange, the measured PIM level achieves a maximum improvement of 30 dB, which is almost unaffected by surface plating materials and connection pressure. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
39. Simulation of PIM generated on the mesh reflector.
- Author
-
Bai, He and Cui, Wanzhao
- Published
- 2015
- Full Text
- View/download PDF
40. Investigation of argon ion sputtering on the secondary electron emission from gold samples.
- Author
-
Yang, Jing, Cui, Wanzhao, Li, Yun, Xie, Guibai, Zhang, Na, Wang, Rui, Hu, Tiancun, and Zhang, Hongtai
- Subjects
- *
ARGON , *SECONDARY electron emission , *SURFACE properties , *SPUTTERING (Physics) , *X-ray photoelectron spectroscopy , *ATOMIC force microscopes - Abstract
Secondary electron (SE) yield, δ , is a very sensitive surface property. The values of δ often are not consistent for even identical materials. The influence of surface changes on the SE yield was investigated experimentally in this article. Argon ion sputtering was used to remove the contamination from the surface. Surface composition was monitored by X-ray photoelectron spectroscopy (XPS) and surface topography was scanned by scanning electron microscope (SEM) and atomic force microscope (AFM) before and after every sputtering. It was found that argon sputtering can remove contamination and roughen the surface. An “equivalent work function” is presented in this thesis to establish the relationship between SE yield and surface properties. Argon ion sputtering of 1.5keV leads to a significant increase of so called “work function” (from 3.7 eV to 6.0 eV), and a decrease of SE yield (from 2.01 to 1.54). These results provided a new insight into the influence of surface changes on the SE emission. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
41. The effect of ions on terahertz wave propagation characteristics in plasma sheath.
- Author
-
Li, Shuantao, Li, Jun, Zhu, Zhongbo, and Cui, Wanzhao
- Published
- 2014
- Full Text
- View/download PDF
42. The calculation of electric field for low pressure discharge in air from DC parameters.
- Author
-
Wang, Rui, Zhang, Na, Li, Yun, and Cui, Wanzhao
- Published
- 2014
- Full Text
- View/download PDF
43. Power Synthesis at 110-GHz Frequency Based on Discrete Sources.
- Author
-
Zhao, Jiaqi, Zhu, Zhongbo, Cui, Wanzhao, Xu, Kuiwen, Zhang, Bin, Ye, Dexin, Li, Changzhi, and Ran, Lixin
- Subjects
ELECTRIC power ,FREQUENCIES of oscillating systems ,DISCRETE systems ,TERAHERTZ technology ,MICROWAVE devices ,ELECTRIC impedance - Abstract
Terahertz technology is one of the research fronts in the microwave society. Among many technical challenges, achieving high-power terahertz radiation has been attracting many efforts. In this paper, we investigate the possibility of power synthesis at low-end frequencies of the terahertz gap based on discrete sources. We show that by applying precision digital phase control, such a power synthesis can be achieved, overcoming the difficulty of phase alignment at these frequencies. For demonstration, we implement a 110-GHz prototype system employing solid-state impact avalanche and transit time diodes. Using a simulation- and measurement-based design methodology, the impedance matching of the designed cavity is able to be simultaneously obtained at both the RF bias and the 110-GHz frequency without using any absorbing material. Detailed design, simulation, and measurement of the prototype are introduced and the experimental results comply well with analytical expectations. Analysis shows that with increased wide digital bit width, the proposed approach is able to provide sufficient phase control precision, making it possible to be used in the power synthesis applications at low terahertz frequencies. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
44. A novel method to improve the power capabilities of microwave components.
- Author
-
Wang, Rui, Li, Yun, Zhang, Na, Cui, Wanzhao, Ming, Ye, and He, Yongning
- Published
- 2013
45. Influence of energy distribution of emitted electrons on multipactor discharge.
- Author
-
Zhang, Na, Wang, Rui, Li, Yun, and Cui, Wanzhao
- Published
- 2013
46. The multi-beam antenna with high directivity based on metamaterials.
- Author
-
Hu, Tiancun, Cui, Wanzhao, Dexin Ye, Huangfu, Jiangtao, and Ran, Lixin
- Abstract
In this paper, the four-beam antenna made of anisotropic metamaterial is investigated. Based on the dispersion relationship of anisotropic metamaterial, we give a detailed instruction on the design of multi-beam antenna using metamaterials with proper permittivity and permeability. The radiation property and gain pattern are experimentally obtained based on an experimentally fabricated four-beam antenna, further verifying the effectiveness of design approach. This new design provides an alternative way to design the multi-beam antennas. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
- Full Text
- View/download PDF
47. Performance enhancement of a nulling antenna through an architecture of multiplicative array.
- Author
-
Cui, Wanzhao, Hu, Tiancun, Lili Xu, Jiangtao Huangfu, and Lixin Ran
- Abstract
In this letter, we propose a beam forming architecture for improving the power-inversion algorithm that is most commonly used in nulling antenna systems. To prevent the possible degradation of the original gain of a nulling antenna in the circumstance when there exists strong interference, we multiplex the received signals from the physical radiation elements in digital domain with a power-inversion array (PIA) and a primitive array (PA), and then form the desired radiation pattern by multiplying the outputs from PIA and PA, to obtain expected narrow nulls in the directions of the interference and in the meantime roughly maintain the original gain and the beam shape of the main lobe. Simulation fits well with the analysis, showing the effectiveness of the proposed approach. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
- Full Text
- View/download PDF
48. Analysis of ridge waveguide with substrates of metamaterials with zero index of refraction.
- Author
-
Cui, Wanzhao, Hu, Tiancun, and Zhang, Hongtai
- Abstract
In this paper, based on peculiar electromagnetic characteristics of metamaterials, peculiar properties of ridge waveguide with substrates of metamaterials with zero index of refraction are analyzed. These results provide some interested insights for potential applications. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
- Full Text
- View/download PDF
49. Prediction of multipactor thresholds in passive microwave components using an improved simulation method.
- Author
-
Li, Yun and Cui, Wanzhao
- Abstract
A self-consistent simulation method for the prediction of multipactor breakdown threshold in passive microwave components is presented in this paper. To model the motion of electrons during the entire multipactor process, three-dimensional particle models of primary and secondary electrons are established and a self-consistent algorithm is put forward to drive them. Moreover, the Coulomb repulsion between real electrons is taken into account to improve the simulation accuracy of the self-consistent algorithm through adding the charges and currents induced by the movement of electrons into the source terms of the Maxwell equations and recalculating the field components in each iterative step. The threshold of the multipactor effect in a practical impedance transformer is predicted using this method and relevant multipactor measurements are performed. The prediction threshold matches well with the experimental result, which validates the simulation method. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
50. Space charge effects on multipactor discharge of microwave components.
- Author
-
Li, Yun, Wang, Xinbo, and Cui, Wanzhao
- Abstract
Space charge effects on the multipactor discharge of microwave components have been studied in this paper. As the input power increasing to a level that multipactor avalanche is about to sustain, an oscillating steady state of multipactor electrons is formed due to the mutual repulsion caused by space charge effects. This steady state is proposed as a criterion of multipactor breakdown threshold for microwave components. The theoretical analysis of space charge forces is completed with an approximate model. Simulation results of practical microwave devices show that steady states can be sustained with affection of space charges, which is drastic as the input power going up to a critical level for multipactor breakdown. Employing this method, threshold of multipactor breakdown for microwave components can be predicted precisely. [ABSTRACT FROM PUBLISHER]
- Published
- 2011
- Full Text
- View/download PDF
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