Dielectric measurement of high-loss liquids in rectangular waveguides

The note extends for use in rectangular waveguides a method of measuring the dielectric constants of high-loss liquids previously described by Bennett and Calderwood.     

激光法在测量矩形截面三分支管湍流流场中的应用

利用三维粒子动态分析仪（３Ｄ－ ＰＤＡ） 测得了矩形截面三分支联接的三维速度分布。在测量中,经过理论分析与对比试验,选择了蚊香烟雾作为散射粒子。实验结果揭示了三分支管的一些流动特性,为进一步的研究打下了基础     

In vitro and in vivo measurement for biological applications using micromachined probe

We developed a small-sized micromachined probe for the measurement of biological properties using microelectromechanical systems (MEMS) technology. We also experimentally showed the suitability of the micromachined probe for biological applications through in vivo, as well as in vitro measurements of various types of tissue. We measured the permittivities of 0.9% saline and the muscle and fat of pork using the micromachined probe after liquid calibration. The measured permittivities of 0.9% saline and pork agreed well with both the expected values of the Cole-Cole equation along with the measured values obtained through the use of a 1-mm-diameter open-ended coaxial probe. We also performed in vivo measurements of breast cancer tissue implanted in an athymic nude mouse to show the suitability of the small-sized micromachined probe for practical biological applications. Through the obtained data, the capability of the micromachined probe of distinguishing different tissue types from one another was shown. The actual aperture size of the micromachined probe is only 240 /spl mu/m /spl times/ 70 /spl mu/m and, therefore, we can extract the biological information from very small biological tissues and drastically decrease the invasiveness of this method through the implementation of the small probe created through the use of MEMS technology.     

小型化大气二氧化碳垂直廓线测量系统标定

通过Li-7500分析仪对小型化大气CO2探测系统进行标定和误差分析。首先,依据4天的测量数据标定CO2体积比浓度,系统采集的吸收度与Li-7500 CO2分析仪测量的CO2体积比浓度满足线性关系,得到的CO2体积比浓度标定系数一致性较好;其次,利用平均后的数据对系统标定,反演得到的CO2体积比浓度相对误差绝对值小于2.0%,与Li-7500 CO2分析仪数据相关性系数大于0.9,充分表明了系统的稳定性和可靠性;最后,根据温度变化对大气传输效应的影响,分析了合肥市科学岛近地面CO2的昼夜变化特征,结果表明近地面CO2体积比浓度变化与温度变化有较强的负相关性。综上证明了标定结果的准确性,为后续测量CO2垂直分布廓线提供了数据支持。     

In-vivo measurement of swine myocardial resistivity

We used a four-terminal plunge probe to measure myocardial resistivity in two directions at three sites from the epicardial surface of eight open-chest pigs in-vivo at eight frequencies ranging from 1 Hz to 1 MHz. We calibrated the plunge probe to minimize the error due to stray capacitance between the measured subject and ground. We calibrated the probe in saline solutions contained in a metal cup situated near the heart that had an electrical connection to the pig's heart. The mean of the measured myocardial resistivity was 319 ohm x cm at 1 Hz down to 166 ohm x cm at 1 MHz. Statistical analysis showed the measured myocardial resistivity of two out of eight pigs was significantly different from that of other pigs. The myocardial resistivity measured with the resistivity probe oriented along and across the epicardial fiber direction was significantly different at only one out of the eight frequencies. There was no significant difference in the myocardial resistivity measured at different sites.     

Radiation from a rectangular waveguide with a lossy flange

The radiation from a rectangular waveguide with a lossy flange coating is studied both analytically and experimentally. An analytic method using Fourier analysis and an impedance boundary condition is proposed. The experiment was performed using a flange covered with a rubber ferrite sheet at an X-band frequency. The numerical and measured results agree well and show that the lossy flange improves the E-plane radiation pattern and the crosspolar radiation. A boresight gain drop of about 2 db is predicted theoretically and measured experimentally     

A generic approach for permittivity measurement of dielectricmaterials using a discontinuity in a rectangular waveguide or amicrostrip line

A generic approach is proposed to accurately measure microwave and millimeter-wave properties of dielectric materials. This novel technique first determines the scattering parameters of a discontinuity containing a material having a wide range of complex dielectric permittivity ϵ that is known a priori (the direct problem). The discontinuity is embedded in a rectangular waveguide or a microstrip line. A unified theory, which is essentially based on a combination of the boundary integral equation technique with a modal expansion approach, is presented to tackle the direct problem. A class of generic diagrams are obtained for interrelating the dielectric permittivity ϵ to its S-parameters, and a simple analytical expression is deduced to solve the inverse problem. The proposed analytical formulation is easy to use and much more rapid than its iterative counterparts. It demonstrates a completely new and efficient strategy for accurate complex dielectric measurements     

Long rectangular patch antenna with a single feed

Radiation characteristics of a long rectangular patch antenna excited by a single feed are investigated. The equivalent circuit of the patch including the feed line section is developed. It is found theoretically that a single feed long rectangular patch supports a leaky traveling wave along the length of the patch. The complex propagation constant of the traveling wave is estimated by solving the wave equation with impedance boundary conditions. Radiation patterns of the antenna are obtained using the principle of equivalence. Various radiation characteristics of center-fed and end-fed long patch antennas are presented     

Diffraction by a rectangular groove with resistive walls

The plane wave diffraction from a rectangular groove having resistive vertical walls with material loading is analyzed for E polarization by using the Fourier transform technique. The problem is formulated into a modified Wiener–Hopf equation applying boundary conditions. The modified Wiener–Hopf equation is solved via the factorization and decomposition procedure. The scattered field is evaluated by taking the inverse Fourier transform and applying the saddle point method. Numerical results on the backscatter radar cross-section (RCS) patterns are presented for various physical parameters.     

Admittance of a rectangular slot which is backed by a rectangular cavity

The rectangular cavity backed slot is excited by a current source connected across its center. The longitudinal voltage variation across the slot is obtained from the variational solution of an integral equation. For shallow and narrow cavities the slot appears inductive and the voltage is rapidly attenuated along the slots. The slot may resonate for deeper and/or wider cavities, when the voltage along the slot is approximated by a half-cycle of a sine wave. The resonant cavity depth and the antenna bandwidth are examined for various cavity and Slot parameters. Dielectric cavity loading is shown to decrease both the resonant cavity depth and the antenna bandwidth.     

Shielding effectiveness of a rectangular enclosure with arectangular aperture

An analysis is presented of the shielding effectiveness (SE) of a rectangular enclosure with an aperture in one face. The enclosure is treated as a length of rectangular waveguide and the aperture as a length of coplanar strip transmission line. Theoretical values of SE agree with measurements for a range of enclosures, apertures and frequencies. The variation of SE with position in the enclosure is also correctly predicted     

一种小型化纳米级单光栅位移测量系统的研制

随着纳米技术的广泛应用以及人们对纳米位移测量认识的不断深化,光栅位移测量技术正在受到广泛的关注。在研究反射式光栅位移测量原理的基础上,设计并实现了一种小型化纳米级单光栅位移测量系统,对系统总体设计、光路布局以及软件算法进行了阐述,最后,利用电容位移传感器ASP-10-ILA等辅助仪器进行了对比实验。实验结果表明:在两路信号不完全正交的情况下系统也能实现准确测量,且理论上系统的位移测量分辨率达到1 nm;在电容位移传感器的量程范围内进行小位移对比试验,系统测量均值与参考值最大偏差118 nm,且与拟合直线偏差均小于100 nm;当光栅发生10 mm以上的较大位移时,测量结果与均值的偏差均小于5 ppm。     

In vitro simultaneous measurement of refractive index and thickness of biological tissue by the low coherence interferometry

We proposed and demonstrated in vitro simultaneous measurement of refractive index and thickness of biological tissue. The technique is based on the low coherence interferometry combined with precise translation stages. Refractive indices were determined with the accuracy of less than 1% for tissue samples of a few hundred micron thickness, including chicken tissue, human tooth and nail. Simultaneous measurement of refractive index and thickness of multilayer tissue are also demonstrated.     

一款小型化S频段高谐波抑制功率放大器的设计

为了确保卫星系统电磁兼容性满足要求,设计了一款应用于卫星测控通信系统的小型化S频段高谐波抑制功率放大器。通过在功放输出端设置谐波抑制网络改善了电路的谐波抑制性能。采用集总与分布参数元件相结合匹配形式,实现了电路的小型化设计。电路尺寸38.5 mm×28.2 mm。通过对功放腔体结构进行细化建模仿真,确保了功放电路的稳定性。实测结果表明,当工作频率为2.52 GHz时,功放1 dB压缩点大于31 dBm,谐波抑制度大于61 dBc,功率附加效率高于35%,1 dB带宽大于320 MHz。与国内外同类产品相比,该功放在谐波抑制性能等方面具有明显优势。     

一种用于WSN的微小型UWB雷达天线设计

超宽带雷达不受雨、雪、声、风等自然环境的干扰,可用于无线传感器网络并全天候工作;在通信领域,超宽带雷达可避免多径干扰问题,解决无线传感器网络在复杂多径环境中的应用局限问题。故超宽带雷达可以与无线传感器网络形成天然的结合。为满足无线传感器网络低功耗、体积小的要求,设计了一种微小型超宽带雷达天线。该天线为共面波导方式馈电的贴片式微带天线。仿真结果表明,天线具有体积小、带宽广(1.78~2.38 GHz)、全向性好的优点,满足无线传感器网络应用需求,并可避免与已用无线通信频段的干扰,具有广阔的应用前景。     

In vivo measurement of surgical gestures

Virtual reality techniques are now more and more widely used in the field of surgical training. However, the realism of the simulation devices requires a good knowledge of the mechanical behavior of the living organs. To provide perioperative measurement of laparoscopic surgical operations, we equipped a conventional operating grasper with a force sensor and a position sensor. The entire apparatus was connected to a PC that controlled the real-time data acquisition. After calibrating the sensors, we conducted three series of in vivo measurements on animals under video control. A standardized protocol was set up to perform various surgical gestures in a reproducible manner. Under these conditions, we can assess an original tool for a quantitative approach of surgical gestures' mechanics. The preliminary results will be extended by measurements during other operations and with other surgical instruments. The in vivo quantification of the mechanical interactions between operating instruments and anatomical structures is of great interest for the introduction of the force feedback in virtual surgery, for the modeling of the mechanical behavior of living organs, and for the design of new surgical instruments. This quantification of manipulations opens new prospects in the evaluation of surgical practices.     

Guided modes in a rectangular waveguide with semiconductor metamaterial

The dispersion equations of bulk modes and surface modes in a rectangular waveguide of semiconductor metamaterial are derived by a modified "Marcatili's method".The cutoff frequencies of the lowest TM bulk mode are discussed,and the Brillouin diagrams of different bulk modes are drawn.They demonstrate that different heights correspond to different guidance frequency ranges which have no superposition with each other and a waveguide with a larger height possesses a wider passband of light.In addition,tendencies of degeneracy for different modes are observed.Finally,the existence of surface modes is verified by a graphical method.     

In vivo measurement of tumor conductiveness with the magnetic bioimpedance method

A noninvasive electromagnetic method has been developed that can effectively measure the in-vivo conductivity difference between rat tumor lines having a low and high metastatic potential. These tumor lines are used in the study of human prostate tumor.     

Field of a rectangular loop

Design advantages of square- and rectangular-loop antennas make these types of antennas attractive for use in mobile devices to improve their communication capabilities. However, modified characteristics of such antennas require additional analysis to evaluate interaction with antennas of other types and other components of mobile devices and human organisms. In this paper, the azimuth and radial field components of a rectangular-loop antenna in near and far fields are calculated and the results are compared to the elementary circular-loop antenna's field. It is demonstrated that loop dimensions and shape substantially affect its field magnitude, especially in the near field.