An iterative technique to achieve enhanced spectral resolution

An iterative technique, called iterative MUSIC (ITM), is introduced that achieves enhanced resolution performance equivalent to MUSIC's without performing the eigensystem decomposition of the array correlation matrix. The technique can be modified to accommodate a signal-space or a noise-space spectral resolution algorithm. Simulation results are included that compare the relative performance of the derived iterative technique and MUSIC. It is shown that the spectral estimation performance of ITM with three iterations is similar to that of MUSIC for signal-to-noise ratios in the range from 0 to 30 dB     

CODYMOS frequency dividers achieve low power consumption and high frequency

Frequency dividers made with complementary dynamic m.o.s. (CODYMOS) circuits require only a small number of transistors and interconnections, a single input signal and operate with a minimum number of successive transitions. This leads to a drastic reduction in stray capacitance and current consumption, and to an increase in speed. A simplified analysis of these quantities is given for binary and ternary dividers. An experimental circuit, integrated with silicon-gate technology, operates from a 1.35 V battery, divides by 3 up to an input frequency in excess of 20 MHz and draws a current of 0.4 ?A/MHz.     

基于FPGA实现简易数字频率计的设计

简易数字频率计的设计,采用FPGA实现对模数转换芯片A/Dtlc549的控制,对外来信号采样,实现信号从模拟到数字的转换,在单位时间内通过计数器的累加实现对频率的计数。该设计实现的频率精度为1Hz,测量范围为0～100MHz,经实际电路测试,仿真结果表明,该频率计具有较高的实用性和可靠性。     

A novel technique to achieve unity power factor and fact transientresponse in AC-to-DC converters

This paper presents a novel power factor correction technique for single-phase boost type AC-to-DC converters in continuous conduction mode. Instead of using the inductor current or switching device current, in this paper, the diode current in the boost converter is used to formulate the duty ratio of the switch in a special way which makes the input current sinusoidal and in phase with the input voltage. To improve the dynamic performance and minimize the input current harmonic components, a new double-injection compensation method is employed in the voltage feedback loop. The power factor corrector has the following advantages: (1) operation with constant switching frequency; (2) elimination of input voltage sensing, error amplifier in the current loop and multiplier in the output voltage feedback loop; (3) minimal total harmonic distortion in the input current; (4) fast dynamic response of the output voltage loop; and (5) simple implementation of the control circuit. The principles of operation of the proposed control scheme are explained. Simulation and experimental results are presented to verify the feasibility of the control strategy     

A bipolar population counter using wave pipelining to achieve2.5× normal clock frequency

Wave pipelining is a technique for pipelining digital systems that can increase clock frequency in practical circuits without increasing the number of storage elements. In wave pipelining, multiple coherent waves of data are sent through a block of combinational logic by applying new inputs faster than the delay through the logic. The throughput of a 63-b CML (current mode logic) population counter was increased from 97 to 250 MHz using wave pipelining. The internal circuit is flow-through combinational logic. Novel CAD methods have balanced all input-to-output paths to about the same delay. This allows multiple data waves to propagate in sequence when the circuit is clocked faster than its propagation delay     

Sapphire substrate-transferred nitride-based light-emitting diode fabricated by sapphire wet etching technique

In order to investigate the influence of a sapphire substrate on the GaN-based light-emitting diode (LED) performance, sapphire-etched vertical-electrode nitride-based semiconductor (SEVENS) LEDs are fabricated by a sapphire wet etching technique. The performance of SEVENS-LEDs is substantially dependent on the presence of sapphire substrate. The light-output power of a SEVENS-LED with a microroughened surface structure and without a sapphire substrate (type-A) is not saturated up to a junction current as high as 300 mA, constituting a notable improvement relative to that (250 mA junction current) of SEVENS-LEDs with a 5 μm-thick sapphire substrate (type-B). The 200 mA light-output power of type-A SEVENS-LED is 1.8 times stronger than that of type-B SEVENS-LED. With increasing junction current, the variation of the peak wavelength is less for the type-A SEVENS-LED than for the type-B SEVENS-LED. These results imply that even a thin sapphire substrate on the SEVENS-LED affects the heat dissipation characteristic at high injection levels.     

Observation of whispering-gallery mode splitting in spherical resonator

We report the observation of the splitting of whispering-gallery mode in the silica spherical resonator. To characterize the fused-silica spherical resonator,an evanescent fiber taper coupling technique is employed. The coupling system consists of a fiber taper with a diameter of about 2.8 microns and a fused-silica spherical resonator with a diameter of about 143 microns. By injecting the laser power into the fiber taper,a number of narrow absorption peaks with equal peak spacing of 3.7 nm are observed in a wide spectral range. After replacing the resonator by the other one with the shape being slightly modified,whispering-gallery mode splitting in the spherical resonator is observed. The wavelength spacing between adja-cent peaks is 0.32 nm,much smaller than that of the previous one.     

Modeling based real frequency technique

Usually commercially available software tools are used, to design matching networks for wireless communication systems. But a properly selected matching network topology with good initial element values must be supplied to these tools. Therefore, in this paper a modeling-based real frequency technique (M-RFT) is presented, to generate matching networks with initial element values. In the proposed method, output impedance data of the matching network are obtained in terms of ABCD-parameters of the load model. Then, they are modeled which in turn yields the desired matching network with initial element values. It is not needed to select a circuit topology for the matching network, which is the natural consequence of the matching processes. Also, there is no need to select the desired transducer power gain level; the proposed technique naturally provides a gain curve fluctuating around a flat level. Eventually, the initial design is improved by optimizing the performance of the matched system employing the commercially available computer aided design (CAD) packages. An algorithm and example are given, to illustrate the utilization of the proposed technique.     

锁相技术在高频开关电源中的应用

本文介绍了锁相技术在电流控制两态调制技术的高频开关电源中的应用。开关电源整个控制环路相当于一个锁相环,这个环路不仅有锁相作用,而且还有调压作用。实验表明,这种高频开关电源有优良的性能。     

应用于微小卫星平台的太赫兹分频技术研究

基于微小卫星组网编队技术,气象预报工作在时间和空间分辨率方面得到大幅提升.为了完成微小卫星大气微波探测仪射频部分的频率分离功能,采用体积小、插损小的波导双工器来实现.采用等效电路法和模式匹配法优化参数,设计了一款166/183 GHz双工器.考虑到实际加工情况,仿真过程中具体分析了膜片陡直度和膜片厚度对双工器性能的影响.加工过程中,通过对器件分割方式和加工缺陷的分析,不断优化加工方案,最终得到满意的加工样品.经测试,166/183 GHz双工器的带内插损小于1. 5 d B,回波损耗大于15 d B,带外抑制高于27 d B以上,仿真结果与实测结果相吻合,证明了双工器设计方法的可行性.     

APPLICATION OF FREQUENCY DOMAIN TECHNIQUE IN HLS

The paper introduce the measurement of some beam parameters for Hefei Light Source(HLS)by frequency domain technique ,which include the betatron tune, average beta function ,natural chromaticity,corrected chromaticity ,and center frequency.Additionally ,the measurement of the influence of DC clearing electrodes on the betatron tune shift is also described.Some measurement results are given .The measurement results are compared with the theoretical values and shoen to be in good agreement.     

Intensity to frequency conversion technique in intensity modulated fibre optic sensing systems

A novel sensing technique based on intensity to frequency conversion is explained and demonstrated. Experimental data are presented and a comparison with a theoretical model is made.<>     

数字电视中的频域频率同步技术

提出了一种宽带数字电视地面广播（BDB-T）系统的同步解决方案，重点研究了频域中的频率同步部分，通过对各种算法的仿真分析比较，给出易于实现、节省资源的频域频率同步算法并完成了相应的FPGA硬件电路设计，经BDB—T功能样机在实际无线环境中的传输测试，证明了算法及其电路的良好实际工作性能。     

Approximate approach to the design of shielded dielectric diskresonators with whispering-gallery modes

An analytical method is presented for calculating the resonant frequency and the Q-factor of shielded dielectric disk resonators excited in whispering-gallery modes. The method is based on a single-mode representation of electromagnetic fields in partial regions of the resonator. For high order modes with high degree of energy concentration in the dielectric this method gives a good agreement with experimental results obtained for different sapphire disks at both room temperature and cryogenic temperatures     

Using frequency hopping spread spectrum technique to combatmultipath interference in a multiaccessing environment

The purpose of this paper is to conduct performance analysis for a frequency-hopped spread spectrum multiaccess network which is subject to the threat of multipath interference. Baseband modulation is done through frequency shift keying and signal detection is accomplished by a noncoherent type receiver. The quality of a signal is affected by the channel noise, multiuser interference, and multipath interference. Performance analysis is conducted on the basis of bit error rate. Due to the sophistication of the system exact analysis is not feasible. The accuracy of approximation is checked against simulations. One major discovery Is that when signal-to-noise ratio is low, multipath interference on the contrary may help to enhance the quality of the signal. Another discovery is that when signal-to-noise ratio is high enough, multipath/multiuser interference becomes the bottleneck of performance. The effect of channel noise can be eliminated by maintaining a large signal-to-noise ratio while spread spectrum technique is employed to reduce the effect of multipath/multiuser interference     

Dynamic frequency compensation technique for switched-capacitoramplifiers

A dynamic frequency compensation technique is proposed for an opamp included in a switched-capacitor amplifier with offset voltage effect cancellation. This feature allows the small-signal and large-signal settling times to be significantly improved compared to those obtained when only classical static frequency compensation is used     

Theoretical analysis of whispering-gallery mode dielectric resonator in MM-wave MIC

The whispering-gallery mode (WGM) disk type dielectric resonator used in millimeter wave microstrip integrated circuits has been computed rigorously by the radial mode matching method. The dependence of resonant frequencies of WGM's on the size of shielding box and Q factors of WGM's relating to leakage loss in the case of parallel-plate shielding structure have been analyzed.     

Resonance characteristics of whispering-gallery modes in anelliptic dielectric disk resonator

This paper presents a novel calculation method for resonance characteristics of an elliptic dielectric disk resonator. In the elliptic resonator, electromagnetic energy propagates as a whispering gallery (WG) mode along the edge region of the dielectric disk. In the novel analysis, a local propagation constant of the WG mode at each point of the elliptic disk edge is represented by a propagation constant of a WG mode in a circular disk whose radius of curvature, material constants, and thickness are equal to those of the elliptic disk. Therefore, we can easily calculate the resonance characteristics of the elliptic dielectric disk resonator by applying a conventional technique for the circular dielectric disk. The calculated results of the resonant frequencies and field distribution are well confirmed by experiments     

一种SoC实现ABME的并行结构分析

自适应块大小运动估计(ABME)对于H.264/H.26L的高编码增益具有非常重要的作用,而其复杂的处理算法使其用于实时压缩编码受到很大的限制.本文提出一种在系统芯片(SoC)实现ABME的空间并行结构,其主要思想是将单个16(16宏块的匹配搜索分成并行16个4(4结构的处理单元,所有单元以相同步调同步搜索匹配块并计算每一步的SAD值,接着采用多个独立单元分别计算不同位置、不同数目的4(4子块所拼接成的块(16(8、8(16、8(8等等)对应的SAD及运动矢量,从而找出每种块结构所对应的最优匹配位置及匹配误差,编码器采用拉格朗日函数判据从中选择一种块结构作为编码时的运动估计单元.EDA软件仿真验证了本文算法的可行性及有效性.     

Laser lift-off technique and the re-utilization of GaN-based LED films grown on sapphire substrate

A thin GaN LED film, grown on 2-inch-diameter sapphire substrates, is separated by laser lift-off. Atom force microscopy （AFM） and the double-crystal X-ray diffraction （XRD） have been employed to characterize the performance of Gan before and after the lift-off process. It is demonstrated that the separation and transfer processes do not alter the crystal quality of the GaN films obviously. InGaN/GaN multi-quantum-wells （MQW＇s） structure is grown on the separated sapphire substrate later and is compared with that grown on the conventional substmte under the same condition by using PL and XRD spectrum.