宽频带相位测向系统相位补偿方法

在被动导引头中,角度信息是由微波接收机接收并由后续信号处理机处理后得到的,方法多采用单脉冲体制的相位测向法,相位测向的关键是相位的准确性,由于被动体制工作带宽较宽,增加了系统相位指标的设计难度,需要通过相位补偿的方法提高测角精度。文章介绍了一种用于被动导引头宽频带测向系统的相位补偿方法,分析了方法的可行性,并给出了试验结果。     

宽带重叠微带贴片天线的分析与设计

分析和设计了一种宽频带微带贴片天线应用全波分析法（ＦＷＡＭ）研究表明，双层重叠微带贴片天线（ＳＭＤＰＡ）具有比普通单贴片微带天线宽得多的带宽利用离散复镜像理论（ＤＣＩＴ）精确计算了所涉及的索末菲积分（ＳＩ），其速度比数值积分法（ＮＩＭ）快数百倍通过改进ＳＭＤＰＡ的馈电结构，使其带宽在ｓ≤２时展宽至２２％以上最后，设计了匹配网络，从而使其带宽在ｓ≤１５时达到约２５％     

一种新型宽频带全向天线的设计

全向天线在下一代宽带移动通信中有着广泛的应用．设计了一种新型的交叉馈电宽频带全向天线,通过加宽振子和加载巴伦实现了天线的宽带特性,使用平行耦合双线对两个宽带对称振子进行交叉馈电．通过对半波振子天线的理论分析、HFSS仿真软件的计算和加工并实测得到：天线印制在厚度为1.5mm、介电常数为2.55的介质板上,实测电压驻波比带宽为44.7％(在2.6～4.1GHz范围内天线的驻波比小于2),并且在整个频段内方向图不分裂,在设计的频段内方向图不圆度小于2.3dB,增益大于1.6dB．该天线结构简单,易于加工,实用性很强．     

耦合弯曲-剪切载荷L型压电振子的低宽频特性

针对传统的压电能量采集装置固有频率高、工作频率范围窄及能量转换率低的问题,基于Timoshenko梁理论提出耦合弯曲-剪切载荷的L型压电振子,研究基于L型压电振子的复合压电结构的能量采集特性. 根据无线传感器的作业环境特点,研究L型悬臂梁的长度、宽度及延伸段长等因素对压电能量采集频率、输出电压峰值及能量转换效率的影响规律. 组合不同尺寸L型压电悬臂梁,研究设计回字形布局的阵列式复合振子. 经仿真分析与实验验证结果可知,在0~250 Hz低频环境下,能量采集频率为28~36 Hz、61~68 Hz、92~99 Hz以及103~111 Hz,较等尺寸传统阵列式压电复合振子覆盖频率平均提升了260%.     

Design of the broadband microstrip array antenna for blast furnace surface monitoring

Aiming at the requirements of high-resolution imaging and high integration of the blast furnace radar,this paper presents a method for designing a wideband microstrip array antenna,which broadens the antenna bandwidth through the design of parasitic patches and air layers.By combining multi-input multi-output (MIMO) radar and synthetic aperture radar (SAR) imaging principles,a linear MIMO array is designed,and a near-field simulation imaging experiment is performed on the simulated feed line through the wave number domain imaging algorithm.Simulation results show that the gain of the main lobe of the antenna can reach 14.05 dBi,the reflection coefficient is less than -10 dB,the absolute bandwidth is 5.25 GHz,the operating frequency is 20.67~25.92 GHz,and the range resolution is increased to 3 cm compared with the existing blast furnace radar.The average error of the azimuth direction of the simulated material line imaging is 0.008 m,and the range direction is 0.0011 m.Compared with the traditional microstrip array antenna,this antenna effectively widens the bandwidth,and the range resolution is higher than that of the traditional blast furnace radar.It can accurately obtain the shape information on the simulated material line,and has an engineering application value for blast furnace surface monitoring.     

Design of a miniature broadband internal antenna for PD detection in GIS

According to the analysis of the relationship between the impedance and bandwidth of the dipole antenna, a novel elliptical plane internal antenna feeding by a coaxial line is presented. It consists of an elliptical monopole and a rectangular grounding piece and has the virtues of broad band, high gain and small size. The antenna can be used for ultrahigh frequency (UHF) partial discharge (PD) detection in the gas-insulated switchgear (GIS). The size is achieved by using the simulation software Ansoft HFSS and the optimum size of total antenna is 90mm×45mm. A prototype is constructed and studied, and then measured. The antenna covers a large band from 781MHz to 2.00GHz, with the VSWR less than 2.5 and a max gain of 3.55dB. Simulated and tested results are in good agreement and the radiation pattern and gain characteristics are given.     

Influence of Temperature on Microstructure and Mechanical Property of Si-B-O-N Ceramics Fabricated by in-situ Reaction Method

为满足新型透波陶瓷工程应用需要,利用硼酸脱水得到的氧化硼与氮化硅在 1400～1800 ℃原位反应制备 Si–B–O–N 陶瓷。借助 X 射线衍射仪、X 射线光电子能谱仪、Fourier 变换红外光谱分析仪和扫描电子显微镜研究了热处理温度对 Si–B–O–N 陶瓷物相组成、结构及力学性能的影响。结果表明：氧化硼和氮化硅的原位反应在 1600 ℃以上完成,所得产物为氮化硼和掺杂硼、氮元素的石英玻璃,其体积分数分别为 30%和 70%;原位反应结束后,随温度提高,氮化硼生长速率逐渐加快,晶粒尺寸由纳米级逐渐长大为亚微米级,非晶相中硼、氮元素含量逐渐降低;受氮化硼纳米晶强化作用以及非晶相结构影响,在 1700 ℃获得的 Si–B–O–N 陶瓷力学性能较好。     

改性氰酸酯基复合材料力学和透波性能研究

利用低介电改性剂对氰酸酯树脂进行改性,制备了石英纤维/改性氰酸酯树脂复合材料,利用SEM表征了树脂及其复合材料的断面,并对改性氰酸酯树脂的耐热性能、力学性能、复合材料的力学性能及透波性能进行了研究。结果表明,改性氰酸酯树脂的玻璃化转变温度达到200℃以上,树脂拉伸破坏表现为韧性断裂,拉伸强度、弯曲强度和压缩强度分别在27MPa、69MPa和148MPa以上;改性氰酸酯树脂和纤维的界面结合良好,复合材料的拉伸强度、弯曲强度和压缩强度分别达到447MPa、461MPa和259MPa以上;在0.5~18GHz范围内,介电常数为3.1~3.3,4mm试样的S21小于-1.6d B。     

Broadband dielectric spectroscopy of Nafion‐117, sulfonated polysulfone (sPSF) and sulfonated polyether ketone (sPEK) membranes

Nafion^®‐117, sulfonated polysulfone (sPSF) and sulfonated polyetherketone (sPEK) are characterized using broadband dielectric spectroscopy in the frequency range of 10 MHz–100 mHz. Overall, there are 4–5 relaxation processes in these sulfonated membranes and a comparison of their spectral features allows assigning the relaxation processes. At an optimum amplitude of ～100 mV_rms, all the relaxations are clearly defined as the electrode polarization is minimized. At low temperatures (?130 °C), these membranes show a broad relaxation peak in the mid‐frequency region, which quickly shifts towards the high‐frequency region as the temperature is increased to ?90 °C. This peak is observed in proton exchange membranes for the first time due to the use of low ac amplitude, and it is assigned to the relaxation of the confined water in the micro‐pores. With all the membranes, the peak associated with ? SO₃H group relaxation is observed in the same frequency range at a temperature of ～?80 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44790.     

热透波材料技术研究进展

热透波材料技术是高超声速飞行器实现通讯与精确导航的关键技术,文章从热透波材料体系、热透波材料热电行为和高温电性能测试技术等方面对热透波材料及其相关技术的发展现状进行了简要介绍。在材料体系方面,石英陶瓷及二氧化硅基复合材料是目前应用的主要材料品种,多孔氮化物陶瓷及陶瓷基复合材料是未来发展的重要方向。在热电行为研究方面,对典型氧化物、氮化物、氮氧化物材料热电行为规律及杂质离子对材料热电行为的影响等方面的研究获得重要进展,并获得试验验证。在高温电性能测试方面,近年来突破了1600℃高温宽频测试关键技术,并获得了氧化硅熔融态介电性能实测数据,国外和国内已实现8MW／m^2热透波实时测试。