微波探测人体皮下肿瘤的最佳工作频率

本文讨论应用微波探测人体皮下肿瘤的最佳工作频率。开口矩形波导探头与人体直接接触。诊断结果通过测量探头的微波反射系数而获得。建立时域有限差分法分析模型,分别从探头的穿透深度与分辨率两个方面者分析,获得不同频率下砂的怀可到的最小肿瘤之间的关系曲线,并进一步确定最佳工作频率约在４ＧＨｚ左右,此时探测效果最佳。     

新颖雷达探盗器

笔者用TWH9250型雷达探测模块设计制作了一台探盗器,它具有制作容易、免调试、工作稳定、性价比高等特点,经实际使用效果良好,现介绍给电子爱好者。该深瓷器探测距离在1～7。范围内可调,每受一次触发,电路即会发出105声音很响的模拟警车电笛声来,使盗贼闻声丧胆。工作原理雷达探盗器由探头和主机两部分组成、雷达探头的电路如图1所示,其核心元件为TWH9250型雷达探测模块。平时,环状天线向周围空间发射出微波信号,产生一个微波警戒场。当有人（或移动物体）进入探测范围时,人体反射的有效回波被天线接收,AI内部微波产生电路便…     

微波测一次风煤粉浓度实验探头天线的设计与仿真

微波测量方法作为新兴煤粉浓度测量法中的一种,以其特有的精度高、测量便捷等诸多优点。本文设计了一种用于微波法测量电厂一次风煤粉浓度的微波探头,探头采用单极子天线进行微波的发射与接收,工作中心频率为570mhz,并利用电磁仿真软件Ansoft HFSS对此天线进行了仿真设计和实验分析,结果表明,天线参数良好,基本满足设计要求,可以作为微波探头使用。     

微波电子探盗器

本文介绍的电子探盗器,是由WT931专用微波多谱勒探头与主机构成。微波多谱勒探测比红外线探测在某一些场合有其独特之优点,例如:可对360°的一个圆区域进行探测;因没有透镜而长期安装使用不怕积尘,从而不影响探测距离;对盗贼穿着特别服装也不失误;性价比高等。电原理见图1(a)。WT931多谱勒探头本身设有3.5双芯插座,可直接用立体声插头与其连接,接线     

基于被动干涉微波亮温图像的海面目标探测算法研究

为利用被动干涉微波技术作为我国天基预警体系的重要补充以实现对海面目标的有效探测，该文提出一种基于被动干涉微波图像的海面目标探测算法。首先，建立了海面背景和海面目标的被动干涉微波图像数学模型；其次，详细地介绍了海面目标的探测算法，并仿真验证了算法的可行性；最后，开展了机载实验。理论分析和实验验证均表明:该探测算法是可行性的，能有效地探测到海面目标，且具有较好的探测性能；海面航行的金属目标在被动干涉微波图像中呈现“一高一低”的特征，可利用该特征提高海面目标探测概率。该探测算法可为天基被动干涉微波技术探测海面目标提供参考。     

基于相位和强度调制的微波测频技术研究

为了更好地对微波信号进行频率测量，采用了一种基于相位调制和强度调制相结合的瞬时测频方法。一束连续波光源通过耦合器被分成两路，未知微波信号分别同时经过相位调制器和强度调制器从而对载波进行调制，之后进入两段长距离的单模光纤中。在光纤中由于色散引起的微波功率损耗的特点，可以获得单调变化的频率-幅度的映射关系，继而通过光电探测的微波信号输出功率比得到幅度比较函数；另外还分析与实现了测频范围与测频精确度的优化。结果表明，该方案结构简易，能够快速精准地测量出未知信号的频率，测量范围可以达到0.5GHz~53GHz，测量误差小于±200MHz。该方法可以有效地测量微波信号频率，可靠性强，适用范围广。     

230GHz接收机准光学元件的测试与评价

亚毫米波的辐射传输和探测包括微波和光学技术。由于这一波段的元件尺寸与辐射波长可相比拟,因此采用高斯束理论进行计算和分析比较理想。本文阐述230GHz接收机准光学元件的测试方法,并对组成系统的各准光学元件进行了评价。1.波纹馈源喇叭波纹馈源喇叭由波纹壁产生的理想边界条件能得到对称的E平面和H平面的电磁场     

馈源喇叭罩密封结构的改进设计

对喇叭罩的密封结构进行分析，找出了原设计存在的缺陷。设计了一种新型的结构形式，提高了喇叭罩的使用寿命和系统的密封性能。     

X波段高功率微波宽角相扫阵列天线

根据工程需要，提出了一种X波段高功率微波宽角相扫阵列天线。基于模式转换和阻抗匹配原理，提出了一种适配角锥喇叭天线和SMA连接器的高功率同轴波导变换器，设计了过渡腔体结构调节功率容量，加载金属匹配块实现阻抗匹配，并与阶梯脊波导一体加工，极大地降低结构复杂性。在8.2～8.8 GHz内单元电压驻波比(VSWR)<1.25,功率容量为41.83 kW,与普通喇叭单元相比功率容量得到大幅提升。7×7阵列可实现±30°圆锥扫描，具有较宽扫描特性。该天线易于加工，可实现灵活波束扫描，具有一定高功率微波应用价值。     

介质加载双频方形喇叭的优化设计

研制了一种新型的正交极化介质加载双频方形喇叭,并进行了工程优化设计。它具有结构简单、性能良好、加工和调试方便、重量轻、成本低等优点,有助于进一步加强和完善对介质加载喇叭的研究和应用。     

用于无线电监测的超宽带喇叭天线的研制

研制了一款用于微波频段频谱监测以及测向的,可以覆盖900MHz～11GHz的高增益超宽带喇叭天线。此款天线采用在传统喇叭天线腔体中加入一对渐变的寄生脊的方法,优化馈电部分同轴到双脊波导的转换,实现了同轴到波导的宽带匹配。最终天线实现了数十倍频程内驻波比小于2,增益在8～13dB之间,并且具有稳定的辐射方向图。     

Nondestructive high-resolution microwave imaging of biomaterials and biological tissues

A high-Q near-field probe based on the 2D microstrip line geometry using defected ground structure (DGS) has been proposed and experimentally evaluated for nondestructive characterization and high-resolution imaging of biomaterials and biological tissues. The unique specifications of the probe are as follows; small size, simple fabrication, non-contact with a sample, excellent de-coupling from surroundings and high microwave power is directly coupled into the tissues. Experimental results show that the probe is able to detect the microwave characteristics of thin lossy biomaterials containing water. High resolution microwave images of leaves with different water content have been obtained with amplitude contrast of about 40–50 dB and spatial resolution of about λ/40. Also, a measurement scenario for detection of lipomas with different sizes has been investigated. Results show that the proposed probe can detect the lipoma of a size larger than 5 mm. Finally, an artificial model to detect skin cancer at the early stage is developed using layers of raw chicken skin. Measurement results show that the probe could accurately detect malignant tumor with at least 15 dB magnitude and more than 100° phase contrast from the healthy skin and with about 8 dB contrast from the benign lesions of the same size.     

N槽结构波纹喇叭的理论分析

本文利用空间谐波法导出了N槽结构(每个周期有N个槽)波纹喇叭的特征方程和等效壁导纳的普遍公式,并把这些公式应用于双槽深波纹喇叭,给出了其等效壁导纳的表达式。文章还对一个双槽深波纹喇叭的等效壁导纳、特征值、口面模比和辐射方向图进行了数值计算,并与实验结果比较,两者吻合得很好。     

Wideband transimpedance amplifier using negative capacitance and capacitive feedback

This paper presents a microwave system for heartbeat rate measurement. This system is based on using a vector network analyzer and horn antennas. The system generates a continuous wave signal toward a person’s chest then the reflected signal is analyzed. The phase difference between the emitted and the reflected signals contains information about the chest movement; hence, the heartbeat rate can be extracted. In this work, several scenarios for detecting the heart activity are considered. The first scenario aims to provide a comparative study for using single-antenna and two-antennas microwave systems. Several radiated powers are considered in this scenario. Simultaneously with the microwave system, a wireless electrocardiograph is used as reference in order to determine the accuracy of the system. Measurements are performed in both cases when breathing normally and when holding the breath. The second scenario aims to test the ability of detecting the heartbeat activity of a person while moving. Measurements are performed while the subject walks towards the radar. Modeling is used for this purpose. The operating frequency used is 20 GHz in both scenarios. Signals are processed using wavelet transform and results show the ability to extract the heartbeat rate even with the presence of body movement.     

Effects of ridge depth on characteristics of shieldedvelocity-matched (SVM) Ti:LiNbO3 optical modulators withridge structures

The effects of ridge depth on the microwave effective index, characteristic impedance of the traveling-wave electrode, and modulation bandwidth of shielded velocity-matched Ti:LiNbO₃ optical modulators with ridges are investigated numerically. It is clarified that the driving voltage has an optimum ridge depth (3-4 μm) for various gaps of the electrode, and there are optimum overlaid layer thicknesses at the velocity matching point for given values of the ridge depth     

微波共振探针在测量等离子体密度中的应用

本文介绍了一种可以测量局部等离子体电子密度的微波共振探针法，并给出了它的测量原理、设计方法和实验结果。实验结果表明：由于微波共振探针不受鞘层的影响，因此它比通常的朗谬静电探针对等离子体密度的测量要精确得多。微波共振探针的空间分辨率与它的几何尺寸有关。     

高频馈源喇叭密封罩工艺性能研究

主要介绍了某馈源喇叭特殊的气密性要求及在高频环境下对密封罩的电性能要求,选择使用两面覆铜的高频微波基板作为馈源喇叭的密封罩材料,采用焊接的密封连接方式.并分别从密封罩的结构构成、材料成分、电性能特点、可加工性及焊接强度等方面阐述了此种高频微波基板的经济性和可靠性,完全满足馈源喇叭气密性及透波性性能指标要求.     

一种超宽带高增益的透镜喇叭天线的设计

该文提出了一种适用于微波通讯系统的超宽带(UWB)高增益透镜喇叭天线。该天线由一个E面喇叭天线,一个球面介质透镜和双楔形金属脊构成,并由同轴线馈电及采用HFSS软件仿真。仿真结果表明,双楔形金属脊可有效增加喇叭天线的带宽,有效频率带宽达到2～12 GHz。当仅使用双金属脊来改善喇叭天线的性能时,喇叭天线的增益会下降。文中使用一种球面介质透镜来补偿双金属脊对喇叭天线增益的负面影响。仿真结果表明,该透镜可有效提高喇叭天线在工作频带内的增益。采用透镜和金属脊结构后,该喇叭天线拥有超宽带,高增益和较强的定向辐射性能,可以应用于各类通信系统中。     

High-efficiency microwave reflector antennas—A review

The paper provides a review of current research on microwave reflector antennas with particular regard to those antennas which produce pencil-beam radiation patterns. After a preliminary examination of microwave antennas of different types attention is focused on circularly symmetric antennas with axially symmetric feed systems. This class of antenna accounts for the largest number of applications which include microwave point-to-point communication, satellite communication, and radio astronomy. The choice of optimum feed is considered in more detail and it is demonstrated that metallic feeds with corrugated walls represent the best choice in most cases. Brief reference is also made to dielectric cone feeds which may find a place in future systems. The design of dual-reflector systems is considered in depth and different computer optimisation techniques are reviewed. These include the latest methods of diffraction optimization in which more than one of the antenna specifications is involved. An example is given where efficiency and VSWR are simultaneously optimized.