Feature-Based Fusion of Dual Band Infrared Image Using Multiple Pulse Coupled Neural Network

To improve the quality of the infrared image and enhance the information of the object,a dual band infrared image fusion method based on feature extraction and a novel multiple pulse coupled neural network(multi-PCNN)is proposed.In this multi-PCNN fusion scheme,the auxiliary PCNN which captures the characteristics of feature image extracting from the infrared image is used to modulate the main PCNN,whose input could be original infrared image.Meanwhile,to make the PCNN fusion effect consistent with the human vision system,Laplacian energy is adopted to obtain the value of adaptive linking strength in PCNN.After that,the original dual band infrared images are reconstructed by using a weight fusion rule with the fire mapping images generated by the main PCNNs to obtain the fused image.Compared to wavelet transforms,Laplacian pyramids and traditional multi-PCNNs,fusion images based on our method have more information,rich details and clear edges.

Design and study of a C-band pulse compressor for the SXFEL linac

A C-band RF pulse compressor is in development at SINAP It comprises of two resonant cavities,two mode convertors and a 3 dB power divider.TE_(0.1.15)mode is selected for obtaining higher quality factor Q_0 of the RF pulse compressor cavities,so that the power gain factor can be 3.2,which is supposed to multiply the RF power from 50 MW to 1 60 MW.In this paper,we report our work on C-band RF pulse compressor,namely the design simulation and cold test results.

Numerical simulation of the coupling of ultra-wide band electromagnetic pulse into landmine by aperture

The modern landmine＇s electronic fuse is susceptible to strong interference or can even be damaged by the ultra-wide band electromagnetic pulse（UWB-EMP）. The finite-difference time-domain（FDTD） method in lossy media with cylindrical coordinates is used to study the interactions of the UWB-EMP with the landmine. First, the coupling of UWB-EMP into the landmine shielding shell through an aperture is numerically simulated. Second, the coupled electromagnetic field of mine shells made of different shielding materials and with apertures of different sizes is plotted. Third, the aperture coupling laws of UWB-EMP into shells are analyzed and categorized. Such an algorithm is capable of effectively preventing ladder similar errors, and consequently improving the calculation precision, and in addition to adopting the message passing interface（MPI） parallel method to divide the total calculating range into more sub-ranges, the overall calculating efficiency is greatly increased. These calculations are surely a constructive reference for modern landmine design against electromagnetic damage.

Rabi Sidebands of Dressed Na Atom Excited By a Pulsed laser

The observation of Rabi sideband of Na atom shows the two-level dressed atom model is over simplified.Using a multi-level model and considering the time evolution of the laser pulse the experiment is well explained.

Microstructure,optical,and photoluminescence properties ofβ-Ga_(2)O_(3)films prepared by pulsed laser deposition under different oxygen partial pressures

Theβ-Ga_(2)O_(3)films are prepared on polished Al_(2)O_(3)(0001)substrates by pulsed laser deposition at different oxygen partial pressures.The influence of oxygen partial pressure on crystal structure,surface morphology,thickness,optical properties,and photoluminescence properties are studied by x-ray diffraction(XRD),atomic force microscope(AFM),scanning electron microscope(SEM),spectrophotometer,and spectrofluorometer.The results of x-ray diffraction and atomic force microscope indicate that with the decrease of oxygen pressure,the full width at half maximum(FWHM)and grain size increase.With the increase of oxygen pressure,the thickness of the films first increases and then decreases.The room-temperature UV-visible(UV-Vis)absorption spectra show that the bandgap of theβ-Ga_(2)O_(3)film increases from4.76 e V to 4.91 e V as oxygen pressure decreasing.Room temperature photoluminescence spectra reveal that the emission band can be divided into four Gaussian bands centered at about 310 nm(~4.0 e V),360 nm(~3.44 e V),445 nm(~2.79 e V),and 467 nm(~2.66 e V),respectively.In addition,the total photoluminescence intensity decreases with oxygen pressure increasing,and it is found that the two UV bands are related to self-trapped holes(STHs)at O1 sites and between two O2-s sites,respectively,and the two blue bands originate from V_(Ga)^(2-)at Ga1 tetrahedral sites.The photoluminescence mechanism of the films is also discussed.These results will lay a foundation for investigating the Ga_(2)O_(3)film-based electronic devices.

A flexible ultra-broadband metamaterial absorber working on whole K-bands with polarization-insensitive and wide-angle stability

For potential military applications, a flexible metamaterial absorber(MMA) working on whole K-bands with totalthickness of 3.367 mm, ultra-broadband, polarization-insensitive, and wide-angle stability is presented based on frequencyselective surface(FSS). The absorber is composed of polyvinyl chloride(PVC) layer, polyimide(PI) layer, and poly tetra fluoro ethylene(PTFE) layer, with a sandwich structure of PVC–PI–PTFE–metal plate. Periodic conductive patterns play a crucial role in the absorber, and in traditional, it is designed on the upper surface of PI layer to form LC resonance. Different from commonly absorber, all the patterns are located on the lower surface of the PI layer in this work, and hence the impedance matching and absorptivity are improved in this purposed absorber. The flexible absorber with patterns on lower surface of the PI layer is compared with that on upper surface of the PI layer, the difference and the reasons are explained by absorption mechanism based on equivalent circuit model, and surface current density and electric field distribution are used to analyze resonance peaks. Absorptivity is greater than 90% in a frequency range of 10.47 GHz–45.44 GHz with relative bandwidth of 125.1%, covering the whole Ku, K, Ka, and some of X, U bands, especially containing the whole K bands from 12 GHz to 40 GHz. Radar cross section(RCS) is reduced at least 10 dB in 11.48 GHz–43.87 GHz frequency ranges,and absorption remained about 90% when the incident angle changed from 0°to 55°. The purposed absorber is fabricated,measured, and experiment results show good agreement with theoretical analysis and numerical simulation. After bonded on outer surface of different cylinders with diameters of 200 mm and 100 mm, the absorption of MMA is approximately reduced 10% and 20% respectively, which shows good conformal character with surface of various curvatures. Due to the attractive performance on strong absorption in the whole K-bands, flexible and easy conformal, our design exhibits broad potential application in radar stealth and sensors.

Detection of the spatiotemporal field of a single-shot terahertz pulse based on spectral holography

According to electro-optical sampling theory, we propose a new method to detect the spatiotemporal field of a single- shot terahertz pulse by spectral holography for the first time. The single-shot terahertz pulse is coupled into a broadened chirped femtosecond pulse according to electro-optical sampling theory in the detecting system. Then the reference wave and the signal wave are split by Dammann grating and spread into the interference band-pass filter. The filtered sub-waves are at different central-frequencies because of the different incident angles. These sub-waves at different central-frequencies interfere to form sub-holograms, which are recorded in a single frame of a charge coupled device （CCD）. The sub-holograms are numerically processed, and the spatiotemporal field distribution of the original terahertz pulse is reconstructed. The computer simulations verify the feasibility of the proposed method.

A UWB communication system based on dechirp pulse compression and OOK modulation

In this paper,a novel UWB communication system structure is proposed.The transmitted signal uses OOK modulation and chirp spread spectrum.The received signal first goes through a dechirp pulse compression process,and then is processed with a two-level sliding correlation algorithm for coarse timing synchronization and fine timing synchronization.After the SNR estimation,the signal is demodulated by an energy detection method.An integrated system level simulation model is established,and the performance of this system is evaluated over the AWGN channel,IEEE 802.15.3a CM1 and CM4 channels.The theoretical analysis and simulation results show that this UWB communication system can effectively reduce the sampling rate and signal processing speed at the receiver,and it is more suitable for long-distance and low-rate UWB communications with high spreading gain.

Study on the transient radiation for apertures excited by rectangle pulse

The analytic representation of the transient radiation for an aperture excited by a rectangle pulse is obtained. It shows that the field duration and amplitude depend on the observation distance, the elevation angle, the pulse width of the rectangle pulse and the aperture size.

基于最优频段循环脉冲指数谱的轴承故障诊断方法

针对滚动轴承多故障冲击共振频带的非一致性及相互交叠影响问题,提出了一种基于循环脉冲指数(CPI)谱的轴承多故障同步诊断方法。该方法引入短时脉冲峰值矩的变异系数对轴承故障冲击进行量化表征,结合冗余提升小波包对轴承故障信号进行频带塔式分解与频带信号CPI计算,构建了故障信号的CPI比值谱图(CPIRgram);根据CPI比值最大原则对轴承故障信号的最优共振频带进行自适应选择,并采用最优频段循环脉冲谱对轴承各故障特征频率进行了统一表征。仿真与故障试验分析结果表明,本文方法无需故障先验知识与分解参数的优化设置,在强噪声及随机瞬态干扰情况下,也能够准确地对多故障特征频率进行同步检测,检测出的故障频率与其理论值误差均小于1.6 Hz,且对故障冲击强度大小及冲击模式变化具有较好的鲁棒性,有较好的应用前景。

数字T/R组件发射频谱控制技术研究

现代武器装备单平台集成的各频段雷达、通信等无线电设备数量越来越多,且发射信号均向高功率、超宽带等方向发展,使得雷达与其他设备之间的发射频谱交叠严重,进而导致不同设备之间存在严重的电磁干扰问题。文中针对不同无线电设备收发信号之间的电磁干扰问题进行了分析,重点讨论了数字T/R组件脉冲发射带外频谱分量的产生机理和改善方法,提出了针对性的频谱控制措施,并在某雷达数字T/R组件上开展了试验验证,证明了该频谱控制方法的有效性。

一种L波段300W GaN脉冲功率模块

随着第三代半导体GaN器件技术的不断发展,GaN高电子迁移率晶体管(HEMT)在电子系统中逐步得到了广泛应用。研制了一款小型化L波段300 W GaN脉冲功率模块。研发了满足高压脉冲工作条件的GaN HEMT芯片,采用负载牵引技术进行了器件大信号阻抗参数提取,并以此为基础设计了小型化匹配网络进行阻抗变换。基于高压驱动芯片和开关器件芯片设计了小型化高压脉冲调制电路。测试结果表明,在工作频率990~1130 MHz、工作电压50 V、脉冲宽度100μs、占空比10%下,功率模块脉冲输出功率大于300 W,功率附加效率大于53%,功率增益大于38 dB。功率模块尺寸为30 mm×30 mm×8 mm。

可见光色分复用通信系统研究与实验

针对单色光通信不便用于照明、普通白光通信频谱利用率较低的问题,设计了一个可见光色分复用通信系统。该系统在保持发光二极管(LED)正常照明功能的同时,还具备信息传递功能。在发送端,采用3种具有固定波长的LED进行调制;在接收端,使用与发送端波长相匹配的窄带滤光镜来分离各个信道的光信号。分离后的光信号经由单片光电二极管转换成电信号,这些电信号再经过与预设阈值的比较后,被微控制器接收并解码。测试结果表明:接收端的窄带滤光镜能有效区分来自3个特定波长LED的广播信号;当发送速率低于50 kHz时,眼图效果良好,能够实现稳定的通信;但当发送速率提升至50 kHz以上时,图像会出现错误色块和偏移失真。

基于非线性电路的双频带脉冲波选择性超表面吸收器设计

本文提出一种基于非线性电路的双频带脉冲波形选择性超表面吸波器(MetaSurface Absorber,MSA).设计的双频带MSA单元结构由放置在同一平面上两个形状相同但线宽不同且集成二极管与电阻电容并联的非线性电路的金属方环形谐振器、中间介质层以及金属接地面构成.仿真结果表明,在-20~10 dBm功率范围内,双频带MSA随功率的增加对短脉冲波吸收率先增大再减小.当功率为-5 dBm时,设计的双频带MSA对脉冲波吸收率在3.2 GHz和4.1 GHz分别可达97%和92%,连续波吸收率只有28%和39%.另外,MSA吸收率随脉冲宽度的增大逐渐减小.进一步研究表明,该双频带MSA在功率为-5 dBm的TE模和TM模脉冲波,斜入射角为0°~60°范围内吸收率超过70%.还研究了非线性电路中电阻、电容参数对设计的MSA脉冲波和连续波吸收率的影响.本文所提出的双频带脉冲波选择性MSA显示了其在无线通信以及抗电磁干扰领域具有潜在的应用前景.

基于色散调控氟碲酸盐玻璃光纤的O-U波段平坦光频梳产生

光学频率梳(简称光频梳)作为一种优秀的多波长光源在通信领域具有巨大的应用潜力。通过将光频梳光源与波分复用技术(WDM)、空分复用技术结合(SDM),通信系统可以具有百Tbit/s量级的传输速率,在5G/6G通信、物联网、自动驾驶等方面具有重要的应用价值。目前实现光频梳的方法主要有以下四种,分别为基于锁模激光器产生飞秒光频梳、基于光学微腔产生光频梳、基于电光调制器产生光频梳以及基于行波四波混频产生光频梳。它们各具特点,但均很难同时实现宽光谱、高信噪比、高平坦度、高的单梳齿功率以及梳齿频率间隔大范围可调,这在一定程度上影响了光频梳在光通信领域的应用。本文提出基于受激布里渊激光腔产生种子梳,采用腔外负色散光纤进行脉冲压缩,进一步利用色散调控的高非线性氟碲酸盐光纤进行扩谱,从而实现光频梳产生。数值计算结果表明,通过该系统,我们可以得到重复频率大范围可调、光谱覆盖整个O-U波段且在O-U波段梳齿强度标准差小于5 dB的平坦光频梳,证明了通过基于布里渊激光腔与色散调控高非线性氟碲酸盐光纤的光学系统产生可用于光通信的平坦光频梳的可行性。

L波段全国产化2.5 kW级脉冲模块设计

随着国防和民用技术的迅速发展,高性能的L波段脉冲模块成为雷达和通信领域的关键组件。文章介绍了一个全国产化的2.5 kW级L波段脉冲模块的设计流程。该模块采用先进的射频放大技术和脉冲形成网络设计,结合本土材料和工艺技术的优势,实现模块的高性能和低成本生产。仿真和实验验证表明,设计的模块满足了所有预期的技术参数,包括功率水平、脉冲宽度和效率,通过了严格的质量控制和可靠性评估。

基于微气囊的三部脉象采集腕带设计

针对传统医学中脉诊方法依赖手脑反馈所带来的明显的主观性与个体差异,为提高证候判断的准确性,将现代脉诊学理论与现代传感器技术相结合,设计一种三部脉象采集腕带诊断系统。系统基于微气囊实现设计,使用气泵对三部充气式腕带充气,控制腕带内的气压模拟取脉压力;选用气压传感器,以数字化信号表示脉诊的信息;通过泄气阀排除腕带内气体。设计上位机软件实现系统控制、脉象可视化与存储等功能。系统在临床上经多次测试,准确性与稳定性良好,并能够完整记录患者脉象信息。

基于改进JMA烈度的脉冲型地震强度预测方法研究

为解决中国强震观测台网布设稀疏、脉冲型地震记录少、难以评估某一地区脉冲地震烈度大小的问题,提出了一种预测脉冲型地震烈度的方法,根据历史地震情况、场地条件、地质情况,采取人工合成的方法生成脉冲型地震,研究日本气象厅计测烈度(JMA烈度)与脉冲地震的相关性,并利用中国地震仪器烈度滤波器对JMA烈度方法进行修正。通过算例计算了鲁甸地震53QQC台站的JMA烈度,并绘制了鲁甸地震和汶川地震的烈度分布云图;选取汶川地震部分台站,对比分析改进JMA烈度与典型烈度计算方法。结果表明:从历史地震数据中提取的高频成分与根据场地、地质情况等生成的低频脉冲成分相叠加,可实现脉冲型地震动的人工合成;随着脉冲速度不断增大,JMA烈度呈增大趋势,回归分析结果表明JMA烈度与脉冲速度的对数呈线性关系;随着脉冲周期的不断增大,JMA烈度呈上升趋势,回归分析结果同样显示为线性关系,可见JMA烈度与脉冲地震有较强的关联性,可以用来衡量脉冲型地震动强度;相较于原滤波器,改进后的滤波器有效频带明显更宽,有效频带在0.3~3 Hz之间,能够涵盖中国绝大部分工程结构的卓越频率,有效频带内部更加平坦,而在有效频带外部则呈现更陡峭的响应,更接近理想滤波器的特性。

E-band通信系统中高速并行FIR成形滤波器设计

为实现E-band(E频段)通信系统中的高速成形滤波,在已有快速FIR滤波算法(FFA)基础上,通过快速短卷积迭代以及张量展开算法,设计了一种高速并行FIR成形滤波器,并进行硬件复杂度分析与时延分析。浮点和定点数仿真验证结果表明,所设计高速并行滤波器在硬件实现上可减少21%的乘法运算操作和1314%的时延单元,6比特以上小数量化可达到系统成形滤波需求。