Spectral switches of partially coherent light focused by a filter-lens system with chromatic aberration

It is shown that when partially coherent polychromatic light is focused by a filter-lens system with chromatic aberration, a spectral shift exists in the focused field, and a spectral switch that is defined as a sharp transition of the spectral shift also takes place at some positions of the focused field. The influence of the chromatic aberration of the lens, the coherence of the partially coherent light in the filter (a circular aperture), the radius of the aperture, and the spectral width of the partially coherent light in the aperture on the spectral shift and the spectral switch are investigated in detail. The numerical results show that these parameters affect the spectral shift and the spectral switch significantly. Potential applications of the spectral shift and the spectral switch of the partially coherent light are discussed.     

Optimum antenna configurations for millimetre-wave communications from high-altitude platforms

Clustering sizes, power control strategies and antenna beamwidths, and orientations are investigated for quasi-stationary high-altitude platforms (HAPs) or other aerial platforms operating in the millimetre-wave band. It is shown that considering the carrier-to-noise and interference ratios (CNIRs) when optimising antenna beamwidths and directions can lead to significant increases in minimum CNIR levels (e.g. from 8.7 to 16.9 dB) over the coverage area. It is also shown that the optimum antenna configurations and transmit powers are a function of the weather, and should (if possible) be adjusted during periods of cloud cover and rainfall. In more practical situations in which only the transmit powers from the HAP antennas can be adjusted dynamically, it is shown that the loss in performance is <2 dB relative to the optimum scheme with dynamically adjustable antenna beamwidths and orientations over a wide range of rainfall conditions     

Broadband millimetre-wave passive spatial combiner based on coaxial waveguide

A broadband millimetre-wave passive spatial combiner using a microstrip probe array and an oversized coaxial waveguide is successfully designed and tested. The equivalent circuit approach of transverse electromagnetic (TEM) lines is adopted to synthesise the coaxial stepped impedance transformer from a K connector with the oversized coaxial waveguide and to analyse the microstrip probe array. The equivalent susceptances of the step discontinuities for the power divider are calculated. A four-way coaxial waveguide passive power combining circuit operating at the entire Ka-band is designed, fabricated and measured. Experiments on the four-way passive combiner show that a minimum insertion loss of 0.7 dB has been achieved at about 29.5 GHz. The combiner has shown a bandwidth of 26.5?40 GHz with 10 dB return loss and less than 2.5 dB insertion loss.     

Passive millimetre-wave imaging and how it differs from terahertz imaging

It is well known that millimetre-wave systems can penetrate poor weather, dust and smoke far better than infrared or visible systems. Imaging in this band offers the opportunity to be able to navigate and perform surveillance in these conditions of poor visibility. Furthermore, the ability to penetrate dielectrics such as plastic and cloth has opened up the opportunity of detecting weapons and contraband hidden under people's clothing. The optical properties of materials have a direct impact on the applicability of imaging systems. In the terahertz band solids have absorptions which can be assigned to vibrational modes. Lattice modes occur at the lowest frequencies and polythene, for example, has a lattice mode at 2.4 THz. Solids have no such absorptions in the millimetre bands (30-300 GHz) and image contrast is produced by differences in transmission, reflection and absorption. A novel, real-time, mechanically scanned, passive millimetre-wave imager has been designed. The antenna elements are based on a combination of a Schmidt camera and a conical scanner, both of which have their origins in optical systems. Polarization techniques, which were developed for operation in the centimetric band, are used to fold the optics. Both 35 GHz and 94 GHz versions have been constructed.     

一种有效抑制阵列后方声源的心形指向性传声器阵列

基于心形指向性传声器的波束形成可以有效抑制阵列后方声源的干扰,提高前方声源的识别精度。以平面轮形传声器阵列为对象,借助MATLAB仿真计算,对阵列后方声源波束形成声源识别特性及其抑制方法进行研究。基于除自谱的互谱波束形成算法提出了含有传声器指向性的波束形成算法,对圆形和心形指向性传声器进行不同声源类型的波束形成仿真计算,并针对仿真结果显示出的不足,给出了既能保证阵列平面上最大声压贡献量的识别精度,又能降低旁瓣水平的幅值校正算法。试验结果证明了基于心形指向性传声器的波束形成可以有效抑制后方声源。     

基于EBG结构的基片集成波导超宽带带通滤波器

为拓展带通滤波器的通带带宽,设计了一种基于EBG结构的基片集成波导（SIW）超宽带带通滤波器．该滤波器利用箭头形电磁带隙结构的阻波特性,将不同大小箭头形结构单元蚀刻在SIW上金属面,以获得超宽带通带．所设计的滤波器中心频率在985 GHz,相对带宽为3959%,通带内的最大插入损耗约为154 dB,相比于类似结构的带通滤波器,其带内回波损耗较大,且整体电路面积较小．测量结果与仿真结果基本吻合,有效地验证了该设计方法的有效性．     

Transmission bandpass guided-mode resonance filters

It is shown that the guided-mode resonance effects associated with waveguide gratings can be used to realize transmission bandpass filters. The key idea is the integration of the resonant waveguide gratings into a dielectric multilayer structure that efficiently reflects the off-resonance spectral components while passing the resonant part. This concept is applied to design multilayer transmission bandpass filters with high efficiency, narrow linewidth, symmetrical response, and low sidebands.     

基于互补式多波段带通滤光片的3D投影显示系统

本文提出一个基于互补式多波段带通滤光片的3D投影显示系统,该系统可以使观看者通过特制眼镜获得3D视觉体验。不同于时分复用和空分复用的3D显示系统,该系统借助成对的互补式滤光片实现谱分复用。通过设计可以实现两块滤光片的三对互补通带恰好分别覆盖RGB三色光谱范围,且每对互补通带相互交错几乎不重叠。在本文中,将两台普通的2D投影仪改造成3D投影系统,并测量了该系统的光谱、亮度、串扰等参数,其平均串扰3%,满足3D显示串扰小于10%的基本要求。     

振动的带通控制法

本文介绍一种新的振动主动控制方法，在主动反馈中合理设计补偿器，把被动吸振器转换为带通吸振器，在给定频率范围内，放大频率，使所有这样的频率都发生谐振。如果把这样的吸振器连接到一个振体上，它能把带通范围内的频率全部吸收。该方法需要对吸振器质量的位移进行附加就地控制。本文描述了该方法的设计方法，并给出了模拟控制结果。     

A microfabrication-based dynamic array cytometer

We have developed a microfabricated device for use in parallel luminescent single-cell assays that can sort populations upon the basis of dynamic functional responses to stimuli. This device is composed of a regular array of noncontact single-cell traps. These traps use dielectrophoresis to stably confine cells and hold them against disrupting fluid flows. Using quantitative modeling, we have designed traps with a novel asymmetric extruded-quadrupole geometry. This new trap can be physically arrayed and electrically addressed, enabling our cytometer. Situating an array of these traps in a microchannel, we have introduced cells into the array and demonstrated observation of fluorescent dynamic responses followed by sorting. Such a device has potential for use in investigating functional processes, as revealed by temporal behavior, in large numbers of single cells.     

一种自由溢流式压电圆环阵

文章介绍一种研制成功的自由溢流式质量负载压电圆环阵，该圆环阵由数个短圆环同轴布阵而成。圆环阵的基元(短圆环)是一种开口的切向极化短圆环，短圆环由质量件和压电组件嵌拼而成，这种结构可以有效降低圆环的径向谐振频率；通过调节圆环阵的径长比，可以获得合适的液腔谐振频率，从而有效降低圆环阵的下限频率，拓宽圆环阵的工作带宽，减小发送电压响应起伏。该圆环阵具有低频、宽带、高发送电压响应和大工作深度等优点。     

A high-density coupled-magnetic-film memory array

A high-density coupled-hard-axis (CHA) destructive readout (DRO) magnetic-film device which yields storage density ≥ 6400 cells per square inch and drive currents compatible with ICs is described. A thin word line design is unique in that its own resistance is used as its termination. This thin word line design permits word line grouping on the substrate level resulting in larger spaced fan-out connections. Its relatively easy manufacturing process as batch fabricated arrays, compared with other comparable high-density memory devices, makes it attractive economically. Extensive experimental data has been obtained as to the disturb margins, signal levels, and keeper effect. In the evaluation of the device performance, the worst case disturb conditions are always applied. At operating conditions, signal levels are in the 2-mV range, disturb margins are ± 35 percent for the unipolar case, and ≥ 50 percent for the bipolar case. Domain-pattern studies were also made to gain further understanding of the device performance and stability relative to its magnetic structure.     

Compact receiver module for a 94 GHz band passive millimetre-wave imager

A compact receiver module for a 94 GHz band passive millimetre-wave (PMMW) imaging system is developed. This receiver module consists of an antipodal linearly tapered slot antenna (LTSA) and microwave monolithic integrated circuit (MMIC) with flip-chip bonding assembly that provides high radio frequency (RF) performance at low cost. A new microstrip-slot transition developed for the LTSA/MMIC interface is also presented and the design procedure for the LTSA is discussed, which obtains almost the same E- and H-plane beam widths. In addition, a low-noise, high-gain MMIC is discussed using inverted microstrip lines that are developed. Finally, it is shown that the PMMW imager can generate a millimetre-wave image.     

A scalable addressable positive-dielectrophoretic cell-sorting array

We present the first known implementation of a passive, scalable architecture for trapping, imaging, and sorting individual microparticles, including cells, using a positive dielectrophoretic (p-DEP) trapping array. Our array-based technology enables "active coverslips" where, when scaled, many individually held cells can be sorted based upon imaged spatial or temporally variant characteristics. Our design incorporates a unique "ring-dot" p-DEP trap geometry organized in a row/column array format. This trap design, implemented in a two-level metal process, provides strong and highly spatially localized holding fields enabling single-cell capture for all traps in the array. We release individual trapped microparticles during sorting using a passive transistor-independent approach where we electrically ground the row and column electrodes associated with specific traps in the array. The demand for chip-to-world electrical connections in our arrays scales proportionally with the square root of the number of traps in a given array, delivering a substantial improvement over prior designs. We demonstrate capture, holding, and release operations with both beads and cells in small arrays of this new architecture.     

A design concept of array heads

This paper describes a novel design concept and experimental hardware data of array heads for close-packed track recording. The heads are batch fabricated on wafers in a linear fashion. These 60-turn thin-film inductive heads are designed with 6 μm pitch helical coils and planar side-by-side P1/G/P2 yokes structure. The linear head array is placed along the upstream-to-downstream direction of the track. By skewing the array slightly off the track direction, each head of the array aligns to an individual track. In this case, the track pitch is about 5 μm, which is the yoke height. With this head arrangement, even though a thermal expansion causes the head-to-head distance to increase along the upstream-downstream direction, it does not cause a thermal induced track misregistration problem. The increased head-to-head distance only affects the timing of signals between tracks, which can be compensated by the channel electronics. Thus, the thermal induced track misregistration problem is eliminated using this design. The guard bands between tracks are not necessary, and a close-packed track recording is possible. A state of the art head impedance of the 60-turn head is obtained: 11 Ω and 0.40 μH. The gap-to-gap pitch is 100 μm. The overall head-to-head isolation is greater than 50 dB at 10 MHz. Such a large isolation is realized by suppressing the capacitive coupling between lead wires using a ground plane and grounded wall structures. The tight winding of the helical coils reduces the magnetic coupling between the heads     

A biosensor array based on polyaniline

This paper describes the fabrication of polyaniline-based microsensors and microsensor arrays for the estimation of glucose, urea, and triglycerides. Microelectronics technology has been used to produce gold interdigitated microelectrodes on oxidized silicon wafers. Polymer deposition and enzyme immobilization has been done electrochemically. Electrochemical potential control has been used to direct enzyme immobilization to the chosen microelectrodes and prevent it at other microelectrodes in contact with the enzyme solution. This has enabled the immobilization of three different enzymes on three closely spaced microelectrodes, resulting in a sensor array which can analyze a sample containing a mixture of glucose, urea, and triolein in a single measurement using a few microliters of the sample. This strategy is quite general and can be extended to other enzyme-substrate systems to eventually produce an "electronic tongue".     

Compact bandpass filters in coplanar strip lines

The authors describe a compact bandpass filter design implemented in asymmetric coplanar strip lines. For initial demonstration, it was built on print circuit boards using modified two-pole Butterworth bandpass filter topology. The novel filter design does not use bonding wires, vias or any interconnecting structure. It is not based on quarter wavelength sections either. It uses the creation of an electrode pattern on the coplanar strip electrodes to emulate an equivalent circuit. The pattern is fine-tuned using full-wave simulations. Bandpass filters for 2.4 GHz ISM (Industrial, Scientific and Medical) and 5.15-5.85 GHz UNII (Unlicensed National Information Infrastructure) bands were designed, fabricated and measured. Measurement responses agree well with full-wave simulation results. The electrode pattern can be scaled for different centre frequency and improved with fine-tuning procedure. For chip-level implementation, the filter size can be greatly reduced because of much smaller minimum electrode width