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介绍了离子回旋波加热中天线的研究进展,讨论了传统环天线、相控双环天线及双臂单环天线激发波的频谱特征。使用射线轨迹方法对单通吸收率进行了数值计算,得到环向谱与单通吸收率的关系。由此验证了双臂单环天线有较好的耦合性能。该天线结构简单,能够改善加热性能。     

Computer-assisted design of surface coils used in magnetic resonance imaging. III. The design and construction of two long twin axial antennae for imaging of the whole human spine

Two modified folded dipole MRI surface coils were designed, constructed and tested. These antenna which are long twin axial lines use the effective distributive capacitance resulting from the distance between two longitudinal elements to provide tuning. The principal advantage of this type of antenna is the ability to image longer objects such as vertebrae, spinal cord, and longer portions of the extremities. This type of antenna shows less localized high intensity in the image due to a more evenly distributed current pickup from the sample.

The coils were designed by calculating theoretical magnetic field distribution for the twin axial coils. These were obtained by integrating the Biot-Savart equation. This gave excellent agreement with an MR image of a di-electrically uniform phantom. As antennae of this sort are nonlinear in response, giving rise to an image intensity nonuniformity, computer software for the MR image was developed to correct the image intensity profile over the experimental volume. The software significantly improved the image quality by reducing the saturated intensity of the region near the antenna, thereby revealing detailed structure of the tissue being imaged.     

高功率无移相器自旋转波束扫描天线设计

设计了一种无移相器结构的平板高功率天线,通过辐射层自旋转方式改变口径场相位分布,从而实现空间波束扫描,满足轻质、低剖面集成要求,辐射增益36 dB,波束扫描范围-30°至+30°,GW级功率容量,满足Ku波段工作的系统指标与能力要求。对天线进行了实物加工与测试,测试结果说明该天线具有良好的波束扫描特性和较高的口径辐射效率。无需加载移相馈电网络便可改变波束指向,具有伺服简单,结构紧凑,平面化、低剖面、轻质等优点,可广泛应用于机载、车载、舰载等高功率微波系统的表面共形发射。     

Improving the uniformity of RF-plasma density by a humped variable-gap spiral antenna

This paper develops a humped spiral antenna of top inductively coupled plasma with variable gap. Comparing with planar spiral antennae, it investigates the performance of humped spiral antennae in the calculated electromagnetic configurations and experimental results. It finds that the humped antenna has the improved uniformity of plasma density in the radial direction and the decreased electron temperature in the top inductively coupled plasma. By experimental and theoretical analyses, the plasma performance in the case of humped antennae is considered to be the combined results of the uniform electromagnetic configurations and the depressed capacitively coupling effect.     

集中质量音叉式引力波天线的三自由度模型

本文将文献[1]提出的集中质量音叉式引力波天线的二自由度模型改进为三自由度模型,并给出了模型天线的实验结果。 关键词：     

Transport and photoinduced properties in highly Sr-deficient manganite films

We used the method of finite-difference time domain (FDTD) to study the characteristics of the patch antenna based on a novel periodic structure, and the theory of photonic crystal structure (also photonic band gap [PBG]) structure was introduced. The results obtained show that the surface waves propagating along the substrate surface can be suppressed by the periodic structure due to the influence of its forbidden band, and the energy of the electromagnetic waves is concentrated mainly in the substrate. As a result, the patch antenna based on the periodic structure has a wider bandwidth in comparison with the conventional patch antennae; and a higher gain is reached, so the patch antenna’s performance is improved. Due to such the advantages, the application of patch antennae can be extended in such fields as mobile communication, satellite communication, aviation, etc.     

大气击穿对高功率微波天线的影响

 高功率微波大气传播过程中，天线附近的功率密度最大，容易发生强电离或大气击穿，由此产生“尾蚀效应”等非线性衰减，因此，传输过程中产生的大气击穿限制了高功率微波天线的最大发射功率。通过分析天线近场模型，研究了矩形口径天线和圆口径天线的近场轴向功率密度分布，得到了不同口面场分布下天线的最大归一化功率密度及其最大值所处的位置，并结合大气击穿功率密度阈值计算出锥照圆口径天线的最大发射功率约为148.47 GW。     

集中质量音叉式引力波天线与Vela星引力辐射探测的探讨

本文提出并计算了一种接收Vela星引力辐射的集中质量音叉式机械谐振型低频天线。指出,由于Vela星引力波信号的连续性和单色性,可以采用信号积累方法提高接收灵敏度。最后给出了灵敏度可以达到目前理论估计的Vela星引力辐射强度的天线参数。此种天线也适用于其他低频引力波探测。 关键词：     

The Influence of Weight-Vector Fluctuations on Statistical Properties of an Adaptive Antenna Array with a Fast Recurrent Tuning Algorithm

We present the results of statistical analysis of an adaptive antenna array tuned in accordance with the fast recurrent algorithm of inversion of a sample estimate of the correlation matrix with allowance for weight-vector fluctuations. Using the perturbation-theory methods in the first (Born) approximation, we obtain the spectral-correlation characteristics of the output signal of an antenna array. Fluctuations are shown to result in signal distortions at the output of an adaptive antenna array. Comparing the obtained expressions with the corresponding formulas for the antenna array with a gradient tuning algorithm, we see that for equal convergence rates of the above algorithms, the output-signal distortions are more pronounced for the fast recurrent algorithm. It is also shown that the weight-vector fluctuations are anisotropic for the fast algorithm, i.e., they are absent in the restriction direction, minimal in the interference direction, and maximal in all other directions. The weight-vector fluctuations in an adaptive antenna array with a gradient tuning algorithm are isotropic in the restriction subspace, i.e., they are the same in all directions and are equal in magnitude to fluctuations in the interference direction for the fast algorithm. The weight-vector fluctuations are also absent in the restriction direction for the gradient tuning algorithm.     

Mechanically scanned leaky-wave antenna based on a topological one-way waveguide

We propose a uniform backfire-to-endfire leaky-wave antenna (LWA) based on a topological one-way waveguide under external bias magnetic field. We systematically analyze the dispersion, showing that the proposed structure supports leaky mode arisen from total internal reflection. By means of tuning frequency or magnetic field, we obtain fixed-bias frequency and fixed-frequency bias LWA with continuous beam scanning from backward, broadside to forward direction. More importantly, we, for the first time, demonstrate that this proposed LWA shows mechanical tunability, allowing us to manipulate the radiation direction from backward, broadside to forward direction by mechanically tuning the air layer thickness. The simulated results show that our system exhibits super low 3dB beam width, high radiation efficiency as well as high antenna gain. Being provided such multiple controlled (especially mechanically) beam scanning manners, the present LWA paves an advanced approach for continuous beam scanning, holding a great potential for applications in modern communication and radar system.     

Properties of Carbon Nanotube Optical Antennae

The properties of carbon nanotube as optical antennae have been studied. The equation of current distribution on a single antenna has been obtained by using conventional transmission line theories. The re-radiation lobe pattern of a single antenna and an antenna arrays have been gained by computer simulation.     

Optimal performance at arbitrary power of minimally nonlinear irreversible thermoelectric generators with broken time-reversal symmetry

We investigate the performance at arbitrary power of minimally nonlinear irreversible thermoelectric generators (MNITGs) with broken time-reversal symmetry within linear irreversible thermodynamics, and the efficiency of MNITGs at arbitrary power is analytically derived. Furthermore, a universal bound on the efficiency of thermoelectric generators (TGs) with broken time-reversal symmetry and the arbitrary power is obtained. Some system-specific characteristics are discussed and uncovered. A large efficiency at arbitrary power can also be achieved via the cooperative mechanism between the system parameters. Our results indicate that the broken time-reversal symmetry provides the physically allowed degrees of freedom for tuning the performance of thermoelectric devices, and the physical trade-off region between the efficiency and the power output can also offer the appropriate space for optimizing the performance of TGs.     

Structure and distribution of antennal sensilla of the red imported fire ant

The morphology of the antenna of the red imported fire ant, Solenopsis invicta, was examined by light microscopy, scanning electron microscopy, and transmission electron microscopy. The antennae are sexually dimorphic: the worker antenna has porous sensilla on the two distal segments (the antennal club), whereas the clubless male antenna has porous sensilla on all segments past the pedicel. The major type of porous sensilla on both male and female is sensilla tricodea curvata. However, the male s. tricodea curvata are rather uniform in size, whereas the female s. tricodea curvata vary considerably in thickness. The number of sensilla on the distal segment of the worker antenna increases with segment length. This suggests a possible mechanism by which task assignments in S. invicta could be determined by the presence or absence of sensilla sensitive to specific task-related odor or pheromone cues. The sensilla basiconica have an invariant spatial pattern on worker and queen antennae.     

可调谐的低频连续引力波接收天线的研究

我们设计制造了共振频率在47.3Hz到60.5Hz之间连续可调谐的低频引力波四极天线。天线的重量为498kg,室温时在空气中加上调谐系统后Q值为4.4×10³。木文把天线的振动简化为在自由端附有—刚性质量的悬臂梁的振动。代替弹性力学的繁复计算,用材料力学的简单方法得到了可以满足要求的结果。本文对用机械方法调整频率的可能方案作了比较,并对把四极天线用于探测更低频的引力波的可能性进行了探讨。 关键词：     

Generalized Heisenberg algebra and algebraic method: The example of an infinite square-well potential

We discuss the role of generalized Heisenberg algebras (GHA) in obtaining an algebraic method to describe physical systems. The method consists in finding the GHA associated to a physical system and the relations between its generators and the physical observables. We choose as an example the infinite square-well potential for which we discuss the representations of the corresponding GHA. We suggest a way of constructing a physical realization of the generators of some GHA and apply it to the square-well potential. An expression for the position operator x in terms of the generators of the algebra is given and we compute its matrix elements.     

Chink antenna in the long line approximation

We give proofs for the sinusoidal nature of the current distribution over an insulated chink antenna with allowance for finite dimensions of the antenna, its feeder region, and the layer of environmental inhomogeneity. The problem of tuning of a chink antenna to resonance is considered in detail, and the possibility of detecting the inhomogeneity of the ambient medium by the antenna detuning is shown. Institute of Atomic Energy, Obninsk, Kaluga region, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 4, pp. 432–440, April, 1997.     

Tests of an ICRH Resonant Cavity Launcher with Faraday Shield

A resonant cavity antenna designed to be suitable for ion cyclotron heating in a tokamak has been bench tested. This antenna is a "discrete element" circuit designed to launch the fast magnetosonic wave in a magnetized plasma. The resonant autotransformer design allows matching to the transmission-line impedance. The tuning and matching properties of this antenna have been compared with a simple computer model. The effective transmission of various Faraday shields has been determined by measuring the change in Q of the antenna system with and without the shield. The test results show that the antenna behaves as predicted by a simple computer model and that coolable Faraday shields with high RF transmission can be designed.     

宽带W波段Flaps天线仿真与设计

设计了一种结合了"十"字和圆环的新型宽带W波段Flaps(Flat Parabolic Surface antenna)天线单元。相比于传统的单层Flaps天线单元,新型单元能获得更宽的相位范围且相移精度更高,能有效拓展天线的带宽。利用这种单元设计了94 GHz的单层Flaps天线,仿真结果显示了较好的带宽性能和方向性,中心频率处增益18.2 dBi,在10.6%的带宽内增益下降小于1 dB,实现了较好的宽带性能,为单层W波段Flaps天线的设计提供了一种新途径。     

Antenna subtraction at NNLO with hadronic initial states: initial-final configurations

We extend the antenna subtraction method to include initial states containing one hadron at NNLO. We present results for all the necessary subtraction terms, antenna functions, for the master integrals required to integrate them over the relevant phase space and finally for the integrated antennae themselves. Where applicable, our results are cross-checked against the known NNLO coefficient functions for deep inelastic scattering processes.     

一种用于时间反演通信的亚波长天线阵列设计

基于时间反演电磁波的远场超分辨聚焦特性, 设计了一种亚波长天线阵列, 其天线单元刻蚀有微结构、单元间距为1/20工作波长且信道相互独立. 在保证相似的辐射特性的条件下, 该亚波长天线阵列对比于其他微结构刻蚀所组成的亚波长天线阵列, 具有较好的远场超分辨率聚焦特性. 为基于时间反演的高速率、高质量多天线通信提供了一种有效的终端天线阵列.