Abstract:A four-channel electron beam planar focusing system is designed to meet the application requirements of the planar integrated traveling wave tube for one-dimensional electron beam array focusing. The calculated results of the axial and transverse components of the magnetic field along the axis are compared with the measured results, which confirms the accuracy of Opera software in calculating the magnetic field distribution. In order to compare with the magnetic field distribution in the electron beam channel of the axisymmetric Periodic Permanent Magnet(PPM) focusing system, a model of the PPM focusing system is established, and the tested results are in good agreement with the calculated results. By comparing the longitudinal and transverse distribution characteristics of the magnetic field in the electron beam channel of the planar focusing system and the axisymmetric PPM focusing system, it is shown that the two focusing systems share the same magnetic field distribution characteristics in the electron beam channel, the ratios of transverse magnetic field component to the axial component are both about 0.11 on the circumference at the same off-axis position, and it is expected that the planar focusing system can achieve good focusing of the one-dimensional array electron beam.

Abstract:Millimeter-wave Traveling Wave Tubes(TWTs) have the characteristics of high power, broad band and high gain, and are widely used in modern military electronic equipment, such as radar, high-speed communication and electronic countermeasures, etc. In order to improve the coupling impedance of the Folded Waveguide(FWG) and the engineering applicability, a novel type of ear-FWG is proposed, which increases the coupling impedance in the working frequency band by more than 30% and reduces the loss by 10% compared with the conventional rectangular waveguide. When the ear-FWG W-band TWT operates at 21.9 kV and 210 mA, and the duty cycle is 5%, the output power in the 10.8 GHz bandwidth is higher than 192 W, the peak power reaches 278 W, the electron efficiency and gain reach 6.3% and 44.6 dB, respectively, and the TWT works stably.

Abstract:With the rapid development of terahertz technology, people are increasingly interested in its various applications in communications, spectroscopy, and sensing. The basis for the development and application of terahertz technology is high-performance terahertz sources. Traditional terahertz sources are large in size and require high-power power supply to drive and are difficult to adapt to the development of integrated terahertz technology. Therefore, there is an urgent need to develop micro-terahertz sources with new mechanisms. This paper studies a new type of miniaturized free electron terahertz radiator, which realizes the excitation of terahertz waves based on the interaction of free electrons and the terahertz waves excited in the grating dielectric waveguide structure. This research provides new options for developing efficient on-chip terahertz radiation sources and expanding advanced terahertz applications.

Abstract:In order to meet the demand of THz vacuum devices for miniature electron beam with high current density, a kind of miniature cathode has been prepared by depositing Ta/Zr coating on impregnated scandate cathode surface via dual Ion-Beam-Assisted Deposition (Dual IBAD) and etching an emission zone with a diameter of 100 m via Focus Ion Beam(FIB). Based on the previous study, this paper focuses on the characteristics of anti-emission coating. It is shown in the experimental results that Ta/Zr coating prepared by dual Ion Beam Assisted Deposition(Dual IBAD) can suppress electron emission more effectively and has a longer life time than that prepared by magnetron sputtering. The reasons for the sound anti-emission performance are that composition with high work function is formed in the process of Barium diffusion into the Ta/Zr coating, and that Barium diffusion is effectively suppressed by the high dense Ta/Zr coating.

Abstract:A design of the electro-optical system for D-band Travelling Wave Tubes (TWTs), including an electron gun and a Periodic Permanent Magnet(PPM) focusing system, is presented and verified. The electron gun utilizes the classical Pierce electron gun structure, the outer layer of the cathode emission surface is set with a cathode sleeve to suppress stray emission at the edge of the cathode, and a cylindrical control electrode is used instead of a conical control electrode, and a negative bias is added to the focusing electrode to adjust the compression state of the electron injection. The electron gun can provide a beam current 57 mA with the beam waist radius of 0.068 mm and the shooting distance of 14.9 mm at the beam voltage of 1.9 kV. A sleeve tube is attached on the cathode to block the electron emission from the edge of the cathode. A cylindrical focusing electrode is used in the electron gun for adjusting the beam focusing state. To stably focus and transmit the electron beam in the beam tunnel of 0.15 mm radius, a PPM focusing system is employed. The peak magnetic field is 2.9 times the Brillouin magnetic field to increase the rigidity of electron injection. The simulated result shows the fluctuation radius of the electron beam is less than 0.1 mm. In order to validate the effectiveness of the D-band TWT electro-optical system, the electron gun and the PPM focusing system have been machined and assembled. The experimental results show the beam current is 49.83 mA, and the collector current is 49.6 mA. The beam transmission rate of 99.5% are obtained by carefully adjusting the PPM system, which achieves the design goal.

Abstract:To satisfy the application requirements of sapphire output window for the 170 GHz megawatt-class gyrotron short-pulsed experiment, by calculating the characteristic of reflection and absorbing of Gaussian beam transmitted through sapphire window, a sapphire window unit is designed with low reflection and low loss power. The low reflectance is verified by vector network analyzer that the Voltage Standing Wave Ratio(VSWR)<1.1. The maximum output average power threshold of the sapphire window has been calculated approximately to be 590 W by analyzing the damage mechanism. The 170 GHz gyrotron employing sapphire window is fabricated, and the power threshold calculated theoretically is verified, providing a reliable theoretical basis for the application of sapphire output window used in high power gyrotron.

Abstract:As an important vacuum electron device, the gyrotron has the capability to generate high peak and average powers in the millimeter-wave and terahertz frequency ranges, holding broad prospects of application in fields such as spectroscopy, radar, communication, and biomedical science. However, conventional gyrotrons inevitably face intense mode competition issues, and the introduction of quasi-optical cavity is expected to significantly alleviate the severity of mode competition. In this study, based on the theory of electron gyrotron oscillation, the innovative combination of quasi-optical cavity and sheet electron beam is proposed with the aim of achieving higher output power and efficiency. Simulation results indicate that under conditions of 40 kV electron voltage and an 8.4 T background magnetic field, the designed quasi-optical gyrotron can generate 6.1 kW of output power at a frequency of 220 GHz, with an electron efficiency of 6.1% and stable operation over a certain duration. The proposed structure in this study may provide a novel solution for gyrotron design operating in high-frequency and even higher harmonic regimes, thus furthering its applications in fields such as radar and controlled nuclear fusion.

Abstract:For the physical layer security communication system based on artificial noise, traditional artificial noise is usually generated by using closed-form expressions derived from derivation or numerical optimization methods which both require accurate channel state information matrix to guarantee the secrecy of the communication system. However, the channel estimation error in the real scenarios causes the artificial noise precoding error to reduce the security capacity of the communication system. For this reason, this paper proposes an artificial noise precoding generation method based on deep learning. By taking the channel estimation information with estimation error as input and fitting it with the precoding matrix obtained by traditional numerical solution generated by perfect channel estimation, a well-trained deep neural network that can adapt to the channel estimation error is obtained. Simulation shows that the security performance and robustness of this method when there are errors in channel estimation are better than traditional artificial noise generation systems. Compared with other deep learning methods for physical layer security, the method proposed in this paper has faster convergence speed.

Abstract:Synthetic Aperture Radar(SAR) works all day and all weather, and has a wide application in the field of earth remote sensing. Video SAR expands the spatial dimension information obtained by SAR imaging to the space-time dimension to obtain richer remote sensing information. The low frequency band of traditional SAR leads to long synthetic aperture time, large amount of data calculation, and great difficulty in high frame rate output. However, the low frequency terahertz wave has strong perception on target details and short synthetic aperture, which is especially suitable for video perception of weak targets. A video SAR system working in the W-band is designed, which adopts the solid-state front end system of bistatic continuous wave, with peak output power of 1 W and maximum transmission bandwidth of 1 GHz. The Polar Format Algorithm(PFA) along with Graphics Processing Unit(GPU) processing architecture is employed to realize high frame rate and low delay imaging. The simulation results show that the imaging resolution of the system can reach 0.15 m and the imaging frame rate is 5 Hz.

Abstract:Joint Tactical Radio System(JTRS) is an important communication equipment for all levels of cyberspace capabilities development and construction for US army, which is the major initiative for realizing the advantages of tactical cyberspace. The overview of JTRS is expounded, including the radio evolution and specification of Software Communication Architecture(SCA) standard. Then the radio station of JTRS architecture and typical networking construction are studied in detail. The primary waveforms and related radio stations of JTRS are analyzed and the latest developments are expected. This work can provide reference for the development of new tactical Internet and software defined radio.

Abstract:The test method of split cylindrical resonator is studied in order to realize the nondestructive test of dielectric constant of flat dielectric materials in microwave band. The electromagnetic field analysis theory of split cylindrical resonator is introduced, and the accurate solution of electromagnetic field distribution in the cavity under dielectric loading is realized by using mode matching technology. The exact relationship between the resonant frequency of the cavity and the dielectric constant of the material is obtained. On the basis of theoretical analysis, a split resonator with cavity resonant frequency of 10 GHz is fabricated and compared with the previously developed closed resonator. The relative error of the measurement results of the real part of dielectric constant is less than 1%. Compared with similar foreign products, the real results of dielectric constant are basically consistent, and the measurement result of loss tangent of this device is closer to the reference value. Therefore, the microwave split cavity method can realize the nondestructive measurement of flat dielectric plates, with outstanding advantages such as high accuracy and convenient use. It can accurately test the dielectric constants of various flat dielectric materials with dielectric constant range of 1~20, tangent of loss angle 1×10^-3~1×10^-5 and plate thickness of 0.1~2.0 mm in the microwave frequency band.

Abstract:A Substrate Integrated Waveguide(SIW) is proposed, which bears the advantages of small size, easy processing, high Q value, and low cost, compared with the traditional slot antenna. The radiation characteristics of the proposed antenna can be optimized by adjusting the slot length, slot width, and cavity size. Calculating the model through electromagnetic simulation software HFSS, then the optimal structure of the antenna can be confirmed finally. The simulation results show that the relative bandwidth of this antenna is about 4.5%, the directivity is excellent, the resonance depth at the center frequency point is <-31 dB, and the maximum antenna gain is 5 dBi, which meets the design requirements and verifies the correctness of the design. The proposed SIW waveguide cavity-backed slot antenna broadens the available frequency spectrum of digital communication, which can provide new ideas for future research.

Abstract:For a complex opto-mechanical system related with optics, mechanics, electronics, control, thermodynamics, gas, liquid, etc, it is an unsolved key problem that how to assess the performance of complicated opto-mechanical system. Herein, combined with Analytic Hierarchy Process(AHP) method, grey method, fuzzy method, etc., one intuitionistic G-factor is presented to evaluate the performance of the system. The G-factor has only one value and can be a direct token of the whole system. Through the statistic progress, it can compare single parameter with that of other system.

Abstract:Intelligent unmanned system is one of the important means to seize the information advantage, implement the precision attack and complete special combat tasks in information war. It is also a multiplier of future military forces. How to apply emerging technologies to improve the effectiveness of intelligent unmanned systems in future combat scenarios is one of the important research directions. The relevant background of intelligent unmanned system is introduced. The edge computing technology and its advantages in intelligent unmanned system are analyzed, and then the problems during the application of edge computing technology into intelligent unmanned system are modeled and solved. The effectiveness of the algorithm is verified by simulation experiments.

Abstract:Quantum Cascade Lasers(QCL) are the important laser sources in mid-infrared bands. The tunable mid-infrared quantum cascade laser has been a research focus because of tunable frequency and single longitudinal mode. At present, the tunable frequency of mid-infrared quantum cascade lasers can be realized by the Distributed Feed Back(DFB) grating, the Distributed Bragg Reflect(DBR) grating, the external cavity diffraction grating, etc. The principle and applications of mid-infrared quantum cascade laser are introduced. The progresses of the DFB and DBR tunable quantum cascade lasers, of the external cavity tunable quantum cascade lasers nearly 10 years are summarized. The advantages and disadvantages of various tunable methods are discussed. Finally, the development trends of tunable quantum cascade lasers are prospected.

Abstract:The error of the double-qubit gate operation caused by the noise is an important reason for the reduction of the fidelity of the execution result in the reversible quantum circuit. A strategy for mapping quantum circuits to noisy quantum computing devices is proposed, so as to improve the success rate of quantum circuits on quantum computing devices. This strategy first provides a method for finding the neighbor path of two qubits on a quantum computing device in which the qubits are not fully connected; since the noise of any two neighbor qubits on the neighbor path is generally different, a heuristic function is constructed based on the execution success rate of the double-qubit gate on the nearest neighbor path to estimate the fidelity of the line in the look-ahead window, and the nearest neighbor method with the highest fidelity is selected according to the cost function. After testing multiple Benchmarks, the experimental results show that the proposed strategy improves the fidelity of the quantum circuit by an average of 65.67% and 71.60% respectively compared with the SabreSwap and BasicSwap methods in Qiskit. The proposed method can improve the fidelity of quantum circuits