Acoustic emission occurrence induced from a NbTi superconductingcoil under alternating current operation

Acoustic emission (AE) induced from an alternating current (ac) superconducting coil was studied during operation in liquid helium. The operating current of the coil was increased from zero with a constant ramp rate at a commercial frequency of 50 Hz until quenching in the coil. The AE signals induced from the coil around the time of the quenching initiation were compared with the operating current, the coil voltage, and the phase difference between the current and the voltage in order to estimate the changes in those signals which resulted from the quenching process. The AE signals continued almost at very low levels before the quenching, At the moment of the quenching initiation, the AE signals clearly and drastically rose approximately 10-15 ms earlier than the decrease in the operating current or the phase difference. The AE signals induced by the wire motion during 50-Hz ac operation were also compared with the operating current     

级联法实现宽带LC带通滤波器设计

利用高通、低通滤波器级联可以实现宽带带通滤波器,利用此方法设计了一个工作频段在100～400MHz的LC宽带带通滤波器。将所设计的截止频率为100MHz的高通滤波器HPF以及截止频率为400MHz的低通滤波器LPF级联实现滤波器的宽带化设计。通过分别对HPF和LPF设置带外陷波点使该带通滤波器具有较好的矩形系数、带外抑制效果。ADS仿真结果验证了理论设计的可行性,并通过优化使滤波器带宽达到4倍频程,带内平坦,输入、输出端口匹配良好,滤波器矩形系数达到1.2。     

Practical adaptive notch filter for missile bending mode rejection

A practical adaptive notch filter based on the /spl Hscr//sub /spl infin// bending frequency estimator is proposed to remove the time-varying structural mode of a missile from the rate sensor measurements. Simulation results using flight test data show the reliable bending frequency estimation performance with this new technique.     

A Blocker Filtering Technique for SAW-Less Wireless Receivers

An active filtering technique to remove the out-of-band blockers in wireless receivers is presented. The circuit employs a feed-forward filtering path to produce an arbitrarily narrow frequency response in the low-noise amplifier (LNA), eliminating the need for an external surface acoustic wave (SAW) filter at the receiver front-end. The required notch filtering in the feed-forward path is realized through a receiver translational loop, driven by the same local oscillator (LO) signals used in the main receiver. For the proof of concept, a prototype amplifier in 65 nm standard CMOS, intended for Global System for Mobile Communication (GSM) applications, is implemented. When the filtering is enabled, the amplifier 3-dB bandwidth reduces from 220 MHz to about 4.5 MHz, and a stop-band rejection of over 21 dB is achieved.     

WDM coherent optical star network

The results obtained with a fiber-optical star network using densely-spaced wavelength division multiplexing (WDM) and heterodyne detection techniques are reported. The system consists of three lasers transmitting at optical frequencies around 234000 GHz, spaced at a frequency interval of 300 MHz. The lasers are frequency-shift-key (FSK) modulated at 45 Mb/s. A 4×4 optical star coupler combines the three optical signals. The WDM signals received from one of the four outputs of the star coupler are demultiplexed by a heterodyne receiver. The minimum received optical power needed to obtain a bit-error rate of 10^-9 is -61 dBm or 113 photon/bit, which is 4.5 dB from the shot noise limit. The degradation caused by co-channel interference was measured and found to be negligible when the channels, modulated at 45 Mb/s, are spaced by more than 130 MHz in the IF domain. These results indicate that a WDM coherent optical star network of this type has a potential throughput of 4500 Gb/s     

基于方开环谐振器的双陷波超宽带滤波器

针对超宽带系统易受窄带信号干扰的问题,设计了一种可以抑制无线局域网络(WLAN)和卫星通信信号干扰的双陷波超宽带带通滤波器。该滤波器的主要谐振结构由T型枝节加载的多模谐振器组成,改进的T型枝节增加了两个传输零点,同时减小了滤波器尺寸;通过耦合方开环谐振器,实现了两个陷波特性,调节谐振器尺寸,可以得到所需的陷波频率。测试结果表明,该滤波器的尺寸仅16.7mm×8.5mm,中心频率为6.9GHz,通带为3.0~10.8GHz,陷波中心频率在5.8GHz和8.04GHz,衰减最低点分别为-27dB和-18dB,仿真与测量结果有较好的一致性。     

Densely spaced FDM coherent star network with optical signalsconfined to equally spaced frequencies

The results obtained with a fiber-optical star network using densely spaced frequency-division-multiplexing (FDM) and heterodyne detection techniques are discussed. The system consists of three optical sources transmitting around 1.28 μm, frequency-shift keying (FSK) modulated at 45 Mb/s and spaced by 300 MHz. A 4×4 optical coupler combines the three optical signals. The FDM signals, received from one of the four outputs of the coupler, are demultiplexed by a heterodyne FM receiver. The minimum received optical power needed to obtain a bit error rate (BER) of 10^-9 is -61 dBm or 113 photons/bit, which is 4.5 dB from the shot noise limit. Cochannel interference is negligible for the above channel spacing and modulation rate. The results indicate that such a system has a potential throughput of 4500 Gb/s. The results obtained with two frequency stabilization circuits used to confine these three FDM optical signals to a comb of equally spaced frequencies are also presented     

一种用于短距离无线通信并集成频率合成器的多模式多频带发射机

A reconfigurable multi-mode direct-conversion transmitter(TX) with integrated frequency synthesizer(FS) is presented. The TX as well as the FS is designed with a flexible architecture and frequency plan, which helps to support all the 433/868/915 MHz ISM band signals, with the reconfigurable bandwidth from 250 kHz to 2 MHz. In order to save power and chip area, only one 1.8 GHz VCO is adopted to cover the whole frequency range. All the operation modes can be regulated in real time by configuring the integrated register-bank through an SPI interface. Implemented in 180 nm CMOS, the FS achieves a frequency coverage of 320-460 MHz and 620- 920 MHz. The lowest phase noise can be -107 dBc/Hz at a 100 kHz offset and -126 dBc/Hz at a 1 MHz offset. The transmitter features a C10:2 dBm peak output power with a C9:5 dBm 1-dB-compression point and 250 kHz/500 kHz/1 MHz/2 MHz reconfigurable signal bandwidth.     

激光焊接缺陷声信号的小波分析

利用小波变换对拾取的激光焊接等离子体的 AE信号进行分析 ,通过对比激光焊接的稳定过程及出现间隙、错边缺陷时的 AE信号 ,发现信号的低频分量在缺陷发生时幅值较正常稳定焊接时有较明显的下降 ;AE信号在 156 2～ 6 2 50 Hz频段部分的能量也存在类似现象。利用小波分解技术能够将信号划分到不同的频带范围这一特性 ,可以实现 AE信号的信息分离 ,从而能够提取AE信号的特征信息 ,进而实现对激光焊接的过程控制。     

A time digitizer CMOS gate-array with a 250 ps time resolution

A pipelined time digitizer CMOS gate-array has been developed using 0.5 μm Sea-of-Gate technology. Precise timing signals which are used to sample input signals are generated from 32 taps of an asymmetric ring oscillator. The frequency of the oscillator is controlled by a phase-locked loop (PLL) circuit which runs in the 10-50 MHz frequency range. A test chip has been developed and tested; a time resolution of 250 ps rms at 40 MHz clock was measured. The chip has 4 channels and encoding circuits for both the rising and the falling edges of the input signals. The chip has 128-word dual-port memories, allowing the histories of the input signals to be stored and causing no deadtime for the conversion     

A 50-GHz Phase-Locked Loop in 0.13-μ m CMOS

A 50-GHz charge pump phase-locked loop (PLL) utilizing an LC-oscillator-based injection-locked frequency divider (ILFD) was fabricated in 0.13-mum logic CMOS process. The PLL can be locked from 45.9 to 50.5 GHz and output power level is around -10 dBm. The operating frequency range is increased by tracking the self-oscillation frequencies of the voltage-controlled oscillator (VCO) and the frequency divider. The PLL including buffers consumes 57 mW from 1.5/0.8-V supplies. The phase noise at 50 kHz, 1 MHz, and 10 MHz offset from the carrier is -63.5, -72, and -99 dBc/Hz, respectively. The PLL also outputs second-order harmonics at frequencies between 91.8 and 101 GHz. The output frequency of 101 GHz is the highest for signals locked by a PLL fabricated using the silicon integrated circuits technology.     

A voltage-controlled tunable thin-film distributed RC notch filter

Notch filters are widely used in communication and instrumentation systems not only for eliminating undesired frequencies and for measuring transient harmonic distortions, but also as central components of selective filters and oscillators in feedback arrangements. This paper describes the characteristics of a thin-film distributed RC (DRC) notch filter made from Au/TaN/Y-doped BaTiO₃ (Y-BT)/Pt. The dielectric (Y-BT) and resistive (TaN) films were grown by pulsed laser deposition (PLD). A notch frequency of 2.8 MHz and notch depth of -76.7 dB were measured from zero with a notch resistance (R_N) of 34 Ω. The experimental optimum notch parameters of α=R/R_N =19.7 and x_n=ω/ω₀=33.0 were obtained. Tunability of the notch frequency was observed with an applied DC bias voltage     

Compact Spatial Triple‐Band‐Stop Filter for Cellular/PCS/IMT‐2000 Systems

We propose a novel spatial multi‐band‐stop filter using modified multiple loop array elements to block electromagnetic waves or signals of mobile phones in public facilities. It operates at the following frequency bands: Korean cellular (824 MHz to 894 MHz), Personal Communication Service (PCS) (1.75 GHz to 1.87 GHz), and IMT‐2000 (1.92 GHz to 2.17 GHz). Two frequency selective surfaces with modified multiple‐loop elements are printed on the top and bottom of a pair‐glass pane, which is a pair of glass panes with an air gap between them. A modified multiple‐loop element with a meander line is used to make the size of the filter compact. The simulated and measured results show good agreement, which confirms the usefulness of the proposed tri‐band spatial filter.     

Linearized mixer using predistortion technique

A predistortion technique has been proposed to reduce intermodulation distortion (IMD) generated from the conversion process of a mixer. In this technique, the IMD generated from a mixer in the IF band was cancelled by the controlled RF error signal, which is generated by a predistorter. The magnitude and phase of the RF error signal were properly adjusted through a vector modulator. This linearization technique has been verified by experiment of a down conversion mixer in the cellular band. A two tone test has been performed at the frequency of 836 MHz with 442 kHz separation. The results show that this method improves about 16 dB of IMD3 at -18 dBm IF output power in 10 MHz frequency band and increases about 3.5 dB of P1 dB of the mixer. Simple topology and good performance in linearization of IF signals renders this technique suitable for highly linear frequency conversion in communication systems     

Adaptive digital notch filter design on the unit circle for theremoval of powerline noise from biomedical signals

Investigates adaptive digital notch filters for the elimination of powerline noise from biomedical signals. Since the distribution of the frequency variation of the powerline noise may or may not be centered at 60 Hz. Three different adaptive digital notch filters are considered. For the first case, an adaptive FIR second-order digital notch filter is designed to track the center frequency variation. For the second case, the zeroes of an adaptive IIR second-order digital notch filter are fixed on the unit circle and the poles are adapted to find an optimum bandwidth to eliminate the noise to a pre-defined attenuation level. In the third case, both the poles and zeroes of the adaptive IIR second-order filter are adapted to track the center frequency variation within an optimum bandwidth. The adaptive process is considerably simplified by designing the notch filters by pole-zero placement on the unit circle using some suggested rules. A constrained least mean-squared algorithm is used for the adaptive process. To evaluate their performance, the three adaptive notch filters are applied to a powerline noise sample and to a noisy EEG as an illustration of a biomedical signal     

Time-independent elastic–plastic behaviour of solder materials

For a long time, constitutive modelling of solders has focused onto the elastic and creep properties. Indeed, the creep model describes the behaviour of solder joints under thermal cycling quite properly. However, in applications such as hand held electronic devices or automotive products, the pure mechanical impact like shock, bending and twisting may even matter more than sole thermo-mechanical fatigue.Therefore the time-independent behaviour of SnPb37, SnAg3.5 and SnAg4Cu0.5 has been investigated on flip chip solder joints. In the experimental tests a cyclic triangular strain wave with constant frequency but different amplitudes was used as the load function. This way the test enables to account for Bauschinger effects. The strain wave amplitudes ranged from Δ=0.25% to 4%, the strain wave frequency was fixed at f=1 Hz. The test temperature ranged from T=5 to 50 °C.The test specimen consisted of two silicon chips (3.3 × 3.3 mm²) bonded by 4 flip chip joints (one at each corner). A specially designed Micro Shear Tester has been used for the experiments with this type of specimen. In contrast to similar setups, it is actively compensated for its finite stiffness. Therefore, it is able to record force–displacement hysteresis with a resolution of better than 1 mN and 20 nm, respectively. Based on these measurements, the parameters of the constitutive equations have been evaluated by FEM analysis. This way, the complex stress state within the sample during the test has been considered precisely providing for high accuracy of the parameter extracted.As a typical application, a three point bending experiment has been simulated by FEM applying different constitutive models for the solder material. Comparing the results, it becomes clear: All the three contributions, i.e., the elastic, the creep, and the time-independent plastic material behaviour, are required in the model. Otherwise it would be incomplete and hence insufficient for assisting in the design of today's electronics packages even with respect to the most frequent load cases.     

基于量子级联激光器的自由空间通信

本文展示了基于中红外量子级联激光器的自由空间通信。该系统的基本单元由一个室温下连续工作的分布反馈量子级联激光器和一个中红外探测器组成,通过该系统成功地进行了40MHz正弦波信号和载波为30MHz的调幅视频信号的传输。本研究提供了量子级联激光器用于自由空间光通信的概念性的验证。系统的最高通信频率受限于调制电路带宽,通过使用改进后的调制电路可以大大提升该通信系统的性能。     

Current mode high-frequency KHN filter employing differential class AB log domain integrator

In this study, a current mode log domain differential Class AB biquad filter based on Kerwin–Huelsman–Newcomb (KHN) structure has been synthesized by using the state-space method and by adopting translinear circuits. The proposed circuit can produce second-order low pass, band pass, high pass, all pass, and notch filter characteristics. The circuit is synthesized for high-frequency applications, i.e. around 100 MHz. The natural frequency and Q quality factor of the filter can be tuned electronically by varying the currents of current sources. Moreover, by varying currents of selected current sources, one can change the characteristics of the notch filter to generate general, low pass, and high pass notch filters. The designed circuit is simulated in both time domain and frequency domain in PSpice by using both idealized and NE 600 series type real transistors that are suitable for high-frequency operations. The frequency as well as time domain responses are found to be as expected. In addition to these simulations, THD and noise analysis are carried out. The details of obtained results are given.     

SIW-Based W-Band Low Phase-Noise Injection-Locked Harmonic Oscillator

A W-band planar injection-locked harmonic oscillator (ILHO) based on substrate integrated waveguide (SIW) is implemented. This ILHO has a free-running output frequency around 94.6?GHz while the technique of harmonic extraction from diodes is used as a frequency multiplier. It has an output locking bandwidth of 300?MHz (from 94.45 to 94.75?GHz) as injecting a signal around 47.3?GHz with the fundamental injection-locked behavior, and the output power is more than 5.8 dBm. The combination of simple synchronization with a low-frequency reference signal allows the generation of stable and low phase-noise W-band signals with a fully integrated planar source.     

Frequency-selective scanning of acoustic surface wave

An acoustic-surface-wave point source is obtained when an interdigital transducer with concentric curved fingers is used. An array transducer composed of 80 point sources has been tested. The direction of propagation of the surface-wave beam emitted by this transducer depends on the frequency. A transmitting-array transducer and five receiving transducers are deposited on a quartz substrate. Each of these five outputs corresponds to a given frequency and delay prescribed by the positioning. At 12°, scanning was attained for a frequency variation of 7.6 MHz around a central frequency of about 60 MHz, corresponding to a delay variation of 18.2 ?s.