浅谈移动通信基站天线系统设计

对基站天线的基本原理、天线选型、天线参数设置、天线安装等方面进行了描述，对天线下倾角、分集距离等进行了重点讨论。     

Directivity analysis of ultrasonic waves on surface defects using a visualization method

Ultrasonic testing uses the directivity of the ultrasonic wave, which propagates in one direction. The directivity is expressed as the relationship between the propagation direction and its sound pressure. The directivity of an ultrasonic wave is related to the choice of probe arrangement, testing sensitivity and scanning pitch, and correct measurement of defect size and location. This paper investigated the directivity of ultrasonic waves, which are scattered from a slit defect located in simulated butt weld joint using a visualization method. When the defect size was smaller than the wavelengths, clear directivity in the reflected wave was observed. When the ratio of defect size to wavelength is greater than 1.5, measured directivities almost agree with the theoretical directivity. The directivity of shear waves scattered from the slit defect varied according to probe direction (Far defect, Near defect). The angle of reflection wave became similar to angle of incidence as the height of excess metal in welded joint increased.     

高频超视距混合天地波雷达海杂波特点分析

采用天波发射、地波接收混合体制模式的高频超视距雷达,由于收发站分置,使得其一阶海杂波谱与单一模式下相比呈现出不同的特点。该文简单介绍了这种混合体制雷达的系统构成和工作原理,针对这种体制特有的几何结构推导了其定位原理,结合这种雷达的电磁波传播路径和收发分置的工作模式,推导了一阶海杂波多普勒频率的理论计算公式,分析了一阶海杂波随不同方位而变化的现象,并通过实测数据对理论分析结果进行了验证。     

高功率微波选模定向耦合器的设计制作

本文根据弱耦合函数理论，设计制作了圆波导ＴＭ０ｎ到３ｃｍ波段矩形波导ＴＥ１０模的选模定向耦合器用于高功率微波的测量系统，理论设计与实际测量结果与理论吻合较好 。     

Two-dimensional ultrasonic anemometer using the directivity angle of an ultrasonic sensor

There has been continuous research on the ultrasonic sensors [L.C. Lynnworth, Y. Liu, Ultasonic flowmeters: half-century progress report 1955–2005, Ultrasonics (2006) 1371–1378]. This study used the directivity characteristic based on phase measurement, which ultrasonic sensor has. Transmitter has wide directivity, and in its range of directivity, receivers are located to measure wind direction and velocity. The velocity experiments which are the result of this production system indicate that the system error rate is 2%. The wind direction measurements also give the same result, an error of ±3°. This result is similar to existing anemometers. However, this new anemometer could possibly have a much higher sampling rate, operating circuit and system structure, which could be much simpler than the previous anemometer.     

谐振腔纵向及横向电场的测量

文章介绍了适用于加速腔高次模式电场分布的测量技术。研制了适用于Ｓ波段的高灵敏高方向性的笼子式微扰体，可在其它场分量较强的背景下检测较弱的电场分量。为了避免高方向性微扰体的定位误差，采用了“双线法”支撑微扰体。建立了专用的机械装置可方便地使微扰体在待测区域三维空间中移动，进行纵向或横向电场的测量。     

Dual Band Dual Polarization Directive Patch Antenna Using Rectangular Metallic Grids Metamaterial

In this letter, a kind of metamaterial superstrate based on rectangular metallic grids is presented to enhance the directivity of patch antenna at two frequency bands for two orthogonal polarizations. According to the periodic boundary condition, the influences of its important geometry parameters are investigated in detail by simulating its unit cell. It is found that the transmission peak frequency is intimately related to the size of rectangular metallic grid. Then, a dual band dual polarization patch antenna with metamaterial is studied and compared with conventional patch antenna. It is demonstrated that by introducing the proposed metamaterial superstrate, the gain of the patch antenna is improved by 9.5 dB at 14.1 GHz for x polarization and 12 dB at 15.4 GHz for y polarization, respectively.     

Experimental study of the azimuthal performance of 3D acoustic transmitter stations

Better well logging techniques for geologic investigations are urgently needed to identify and evaluate complex reservoirs.We describe a new type of 3D transmitter station with corresponding circuits and bodies.They can be used in a promising new technique of acoustic reflection well logging,that features better azimuthal detection capabilities,as well as better investigation depth.The transmitter stations consist of three-level subarrays that can radiate acoustic energy in any required azimuth of 3D space by circularly exciting various combinations at different levels.We tested the 3D acoustic transmitter stations and obtained laboratory directivity measurements with the3 D acoustic transmitter stations for the first time.The results show that the 3-d B beam width in the horizontal plane ranges from 59° to 67° as a result of phase-delayed excitation.The main beam is steered in the vertical plane at a deflection angle that ranges from 0° to 16° when the delay time of the excitation pulse between each pair of adjacent arc arrays is gradually adjusted.The 3-d B beam width is equal to 11°,whereas the deflection angle in the vertical plane is equal to 14°.Each of the four third-level subarrays in the same circumferential direction display consistent horizontal and vertical directivities,thus satisfying the requirements of azimuthal acoustic reflection logging.     

岩层蠕滑形成应力集中区特征研究

山体主脊为厚层状石灰岩背斜主轴,北坡相同于岩层倾向倾角。在软弱结构面的作用下,岩层产生了蠕动作用,蠕滑力使坡下岩层穹隆,产生了应力集中区。勘察阶段查出了"饼状"岩芯和透镜体状空洞,施工阶段发生了边坡岩体位移现象。通过发明的监测器,对其记录数据与采石场卸荷区综合分析,从而论证了应力集中区机理,确定了穹隆段应力具有极强的方向性。     

一种新型光子晶体结构的微带天线

提出了一种新型的基于二维光子晶体基底的微带天线,光子晶体结构是人造的周期性电介质结构,本文采用的方法是在电介质中引入周期性分布的空气孔洞,孔洞的分布是三角形点阵,然后在中心孔洞引入缺陷,但只是在中心孔洞的下半部分引入缺陷,即中心孔洞的深度为周围孔洞深度的一半,天线的贴片放在孔洞的底部,即将天线贴片放在了光子晶体内部。我们采用HFSS仿真软件对该结构进行了模拟,数值仿真结果表明该结构对天线的方向性有明显改善。