一种微带结构的新型不等分功分器设计

为了满足天线阵波束赋形对各单元天线输入功率不等分配的要求,基于Wilkinson功率分配器设计理论,详细推导并给出了任意功分比情况下隔离电阻的计算公式,补充了目前参考资料中对于直接多路输出功分器的设计指导。通过引入二分之一波长微带传输线,提出了一种微带结构的新型不等分功率分配器的设计方法。基于此方法,实现了一款应用于海事卫星通信天线阵馈电网络的功分比为1∶2∶1的三路不等分功分器。仿真和实测结果表明,功分器在工作频带范围内具有良好的性能指标。     

一种基于布喇格光栅的可调色散补偿技术

色散补偿型光栅是非周期光栅,采用改变光栅轴向温度场梯度,可使得光栅轴向上不同位置的反射波长发生不同的变化,从而改变啁啾量,达到调节色散的目的.基于这一理论设计了一种基于光纤布喇格光栅的可调色散补偿器,具有无机械调节运动装置,模块可靠性高,色散的调节范围可达到为800ps/nm.     

Magneto-optical measurements with a hybrid magnet

An FFT spectrometer has been constructed to measure magneto-optical spectra in the far-infrared region (3 to 40 cm^?1) with a hybrid magnet system. The magneto-absorption was studied in the spin-Peierls cuprate CuGeO₃ at various magnetic fields. Coil constants of superconducting magnet and resistive one, of which a hybrid magnet consists, were calibrated by ESR spectra at the constant field.     

Design of superdirective arrays with high radiation efficiency

Superdirective arrays have been considered unrealizable due to the high elemental currents required and their sensitivity to small variations in amplitude and phase. A new approach to superdirective array design based on polynomials which optimize radiation efficiency has been devised. An example of the optimization procedure is given for a 2-wavelength 11-element array, and the sensitivities of radiation patterns optimized for directivity and for radiation efficiency are compared. The relationship between radiation efficiency and the number of elements within a given array length is investigated, and an optimum number is proposed. Finally, the variation of radiation efficiency with beamwidth reduction of optimally filled arrays of different lengths is given.     

Design of dipole arrays with equal element impedances

A simple method for synthesising a given radiation pattern from a new type of dipole array, an unequal element array, is described. The input impedances of the elements are the same and the lengths and the radii of the dipoles are different.<>     

Analytical and experimental investigation on the magnetic field and torque of a permanent magnet spherical actuator

This paper presents the torque model of a ball-joint-like three-degree-of-freedom (3-DOF) permanent magnet (PM) spherical actuator. This actuator features a ball-shaped rotor with multiple PM poles and a spherical stator with circumferential air-core coils. An analytical expression of the magnetic field of the rotor is obtained based on Laplace's equation. Based on this expression and properties of air-core stator coils, Lorentz force law is employed for the study of the relationship between the rotor torque and coil input currents. By using linear superposition, the expression of the actuator torque in terms of current input to the stator coils can be obtained in a matrix form. The linear expression of the actuator torque will facilitate real-time motion control of the actuator as a servo system. Experimental works are carried out to measure the actual magnetic field distribution of the PM rotor in three-dimensional (3-D) space as well as to measure the actual 3-D motor torque generated by the actuator coils. The measurement results were coincident with analytical study on the rotor magnetic field distribution and actuator torque expressions. The linearity and superposition of the actuator torque were also verified through the experiments.     

基于嵌入式的气候补偿器在集中供热系统的设计

气候补偿器在集中供热系统中的应用,能够有效降低能耗,能够促进生态文明建设。气候补偿器可以科学有效地解决集中供热系统中换热站处的控制以及管理问题。文中主要研究了气候补偿器的工作原理、作用,并以设计以AMR9 S3C2410为基础的硬件设计与软件设计。     

Gyrotron based on a superconducting magnet

The replacement of conventional pulsed magnetic field coils previously used to generate the intra-cavity B-field with an 11T superconducting magnet is reported. The resulting more stable mm-wave output pulse is shown and the refurbishment requirements of both the field emission, field-immersed, cold cathode and Marx bank spark gaps demonstrated. This system proved to be tunable, oscillating from 20GHz up to 110GHz, with peak power levels of 450kW and 300kW respectively. Other operating parameters were also examined including mm-wave pulse length as a function of anode-cathode position. The pulse length increased from 87±6ns to 310±10ns with a 2.5 cm horizontal transit of the cathode away from the anode. A similar effect was witnessed with the increase of the intra-cavity B-field from 1.00T to 5.00T resulting in the mm-wave pulse duration increasing from 250±40ns. Second harmonic operation of the cavity resulted in ～0.5kW of radiation observed at 96GHz. The pulse-to-pulse mm-wave stability coupled with the mode selectivity of the ohmic-Q-dominated cavity resulted in the identification of several oscillating modes including the TE₁₂, cut-off frequency 21.1 GHz, the TE₀₂, cut-off frequency 29.1 GHz, the TE₃₅ at ～74 GHz and the TE_14,2, at ～88GHz.     

Design and control of a novel spherical permanent magnet actuator with three degrees of freedom

The paper describes the design and control of a new version of a spherical permanent magnet actuator, which is capable of three degrees of freedom and a high specific torque. Based on an analytical magnetic field distribution, the torque vector and back-emf are derived in closed forms. An optimal design procedure is proposed to achieve maximum output torque or maximum acceleration for a given payload. The control of the actuator, whose dynamics are similar to those of robotic manipulators, is facilitated by the establishment of a complete actuation system model and the application of the computed torque control law. The validity of the analysis and design techniques, and the effectiveness of the control strategy, are confirmed by measurements.     

Design of rectangular horn arrays with oversized aperture elements

The possible existence of blind spots, due to forced aperture resonances, is demonstrated theoretically and experimentally at 14 GHz in rectangular grid arrays of tapered rectangular horn elements with oversized (overmoded) apertures. The dominant contributor to these blind spots is the resonance of the equivalent transverse magnetic (TM_12) waveguide mode. The numerical results based upon our approximate methods of formulation and solution of the array boundary value problem agree well with experiments. A method for eliminating the blind spots by proper taper design is presented and experimentally verified. The analytical methods used in this work could possibly be extended to conical horus and other tapered-structure arrays as well as other periodic grid geometries. New simple and accurate formulas for the zeros of Bessel and Legendre functions and their derivatives are obtained as a result of this analysis.     

Single-port-access surgery with a novel magnet camera system

In this paper, we designed, built, and tested a novel single-port access laparoscopic surgery (SPA) specific camera system. This device (magnet camera) integrates a light source and video camera into a small, inexpensive, portable package that does not compete for space with the surgical tools during SPA. The device is inserted through a 26-mm incision in the umbilicus, followed by the SPA port, which is used to maintain an insufflation seal and support the insertion of additional tools. The camera, now in vivo, remains separate from the SPA port, thereby removing the need for a dedicated laparoscope, and, thus, allowing for an overall reduction in SPA port size or the use of a third tool through the insertion port regularly reserved for the traditional laparoscope. The SPA camera is mounted to the abdominal ceiling using one of the two methods: fixation to the SPA port through the use of a rigid ring and cantilever bar, or by an external magnetic handle. The purpose of the magnet camera system is to improve SPA by: 1) eliminating the laparoscope SPA channel; 2) increasing the field of view through enhanced camera system mobility; and 3) reducing interference between the camera system and the surgical tools at the port, both in vivo and ex vivo.     

钴铂纳米线阵列的制备与性能研究

在具有纳米级孔洞的多孔氧化铝模板上,用电化学方法成功地制备了CoPl3纳米线有序阵列复合膜。分别用透射电子显微镜（TEM）、选区电子衍射（SAED）、X射线衍射（XRD）、振动样品磁强计（VSM）和超导量子干涉仪（SQUID）对样品进行测试与表征。形貌观察和物相分析表明,模板中的CoPl3纳米线构成的阵列,排列均匀有序,相互平行;而纳米线中的CoPl3为Ll2无序结构。磁性研究表明,纳米线的无序晶体结构决定了纳米线阵列弱的磁晶各向异性;同时纳米线中部分小晶粒在400K左右表现出顺磁性,导致纳米线阵列居里温度的下降。比较低温和室温下的磁滞回线,低温下有大的矫顽力,从另一方面证明纳米线中的小晶粒确实存在相转变。     

Design and analysis of a 3-way unequal split ultra-wideband Wilkinson power divider

In this article, a 3-way ultra-wideband (UWB) unequal split Wilkinson power divider (WPD) using tapered line transformers is presented. Three tapered lines are designed through the even-mode analysis, and used instead of the conventional 3-way WPD arms. In addition to the three main arms, three additional tapered transformers are used to match the output ports to the 50?Ω connectors. To achieve an acceptable output ports matching and isolation, multiple resistors are uniformly distributed and mounted between the three tapered arms of the WPD. An optimisation process is carried out to obtain the values of these resistors considering the odd-mode analysis. The proposed WPD is designed to operate over the frequency band of 2–12?GHz, and simulated using two full-wave EM simulators. Full-wave simulation and experimental results verify the design procedure.     

Fractile arrays: a new class of tiled arrays with fractal boundaries

In this paper, a new class of antenna arrays are introduced, which we call fractile arrays. A fractile array is defined as any array with a fractal boundary contour that tiles the plane without gaps or overlaps. It will be shown that the unique geometrical features of fractiles may be exploited in order to make available a family of deterministic arrays that offer several highly desirable performance advantages over their conventional periodic planar array counterparts. Most notably, fractile arrays have no grating lobes even when the minimum spacing between elements is increased to at least one-wavelength. This has led to the development of a new design methodology for modular broadband low-sidelobe arrays that is based on fractal tilings. Several examples of fractile arrays will be considered including Peano-Gosper, terdragon, 6-terdragon, and fudgeflake arrays. Efficient iterative procedures for calculating the radiation patterns of these fractile arrays to arbitrary stage of growth P are also introduced in this paper.     

Simulation and fabrication of magnetic rotary microgenerator with multipolar Nd/Fe/B magnet

This study presents a high power rotary-type electromagnetic microgenerator with multilayer planar copper (Cu) microcoil and multipolar hard magnet of Nd/Fe/B. The size of this microgenerator is smaller than 1 cm³ in volume. It can achieve the goal of compact integrated system. The induced voltage is simulated by FEMLAB and MATLAB software to solve the coupling problem, which involves in kinetic and electric issues. The multilayer microcoil is fabricated by MEMS process (micro-electro mechanical system), and the multipolar magnet is fabricated using sintering process. The sintered Nd/Fe/B exhibits an excellent hard magnet with B_r of 1.44 T and H_c of 975 kA/m. Next, the multipolar magnet rotates relative to planar microcoil to induce electric current. The preliminary result shows that maximum induced voltage of 111.2 mV and maximum power of 386.42 μW can be achieved. Besides, the experimental result is compared with simulated one.     

Design of a self-reconfiguring interconnection network forfault-tolerant VLSI processor arrays

An interconnection network capable of spontaneously reconfiguring a VLSI processor array on detection of faulty processors is presented. Although the reconfiguration process is global, the network control circuitry is localized around each processor and is therefore completely modular. The structure of the control circuitry is fixed and thus independent of the array size or the number of spare processors. The network performance in yield enhancement is analyzed through Monte Carlo simulation. The network effectiveness in using surviving processors is close to that of an ideal network (one capable of tolerating as many faulty processors per row as there are spare processors per row). Strategies involved in testing the fault-tolerant array are also presented. Test circuitry is placed around each of the processors to enable testing of all the processors in parallel. The same circuitry is used to test the interconnection network efficiently. The additional silicon area requirements due to the network and the test circuitries are examined through the design of a prototype fault-tolerant array     

A study on wideband gap-coupled microstrip antenna arrays

A method for increasing the bandwidth of microstrip antenna arrays by using gap-coupled patches is described. The input impedance properties of gap-coupled patches are analyzed by the use of the spectral dyadic Green's function for a grounded dielectric slab and the moment method. The dependence of different parameters such as s, L and ϵr on the impedance characteristics is investigated. In considering the effect of feed network, the impedance bandwidth for a VSWR<2 of two-element gap-coupled patch array is as large as 2.5 times that of an ordinary array. The radiation patterns over this bandwidth are measured and discussed. All the microstrip antenna arrays are fabricated on a substrate with ϵr=2.86, h=1.5 mm. A comparison of theoretical and experimental results for both input impedance and radiation patterns are given     

Design of dual-polarized L-probe patch antenna arrays with high isolation

An experimental study of a dual-polarized L-probe patch antenna is presented. The antenna is designed to operate at around 1.8 GHz. A "dual-feed" technique is introduced to achieve high isolation between two input ports. The proposed antenna has an impedance bandwidth of 23.8% (SWR/spl les/2), 15% (SWR/spl les/1.5) and an isolation over 30 dB. In array designs, techniques for improving the isolation between two adjacent elements of an antenna array are also investigated. A two-element array with more than 30 dB isolation is designed and tested.     

A rod matrix compensator for small-field intensity modulated radiation therapy: a preliminary phantom study

A compensator made of a tungsten-based rod matrix has been proposed for small-field intensity modulated radiation therapy. The compensator was attached to a 6 MV linac gantry head. The proposed compensator could modulate the X-ray intensity with a step of 10% and a minimum transmission of 2.5%.     

Design and analysis of a plug-in robust compensator: an application to indirect-field-oriented-control induction machine drives

It is well known that the system performance for an indirect-field-oriented-control induction motor drive degrades under the variation of rotor resistance and in the presence of external load torque. In this paper, a plug-in robust compensator for speed and position control enhancement of an indirect-field-oriented-control induction machine drive is developed. In the case where a controller for the induction machine already exists or is in operation with satisfactory nominal tracking performance, this plug-in compensator, designed using the H/sub /spl infin// loop-shaping techniques, can be plugged into the existing controller without affecting the already satisfactory nominal tracking performance of the existing closed-loop system but with the capability to improve the system performance under plant parameter variations and in the presence of external disturbances. Simulation and experimental results are given to validate the proposed plug-in robust compensator.