An algorithm analog-to-digital converter using unity-gain buffers

An algorithmic stage for bipolar 1-b analog-to-digital (A/D) conversion using a unity-gain buffer is proposed. Cyclic and pipeline A/D converter architectures using this stage iteratively or in cascade are also described. Error analysis and SPICE simulations show that a conversion accuracy higher than 8-b and a conversion rate up to 10 Mb/s are attainable with presently available 3-μm CMOS technologies. Video frequency operation is also possible with finer linewidths. The component requirement is minimum, and thus it is best suited for an analog interface in application-specific integrated circuits (ASIC). A prototype cyclid A/D converter built using discrete components confirms the principles of operation     

Hybrid control approach for the output voltage regulation in buck type DC?DC converter

Buck converter is modelled as a hybrid automaton for the purpose of designing an appropriate control law to regulate its output voltage. The circuit when operated in continuous current mode is pulled into a limit cycle, specified by the regulation specifications, although the switching frequency varies with the load. On the other hand, under light-load conditions, the circuit is pulled into a fixed-frequency limit cycle in discontinuous current mode to satisfy the regulation criteria. Therefore, the controller design is generic in the sense that the required regulation is met throughout the operating range of the buck converter. The control problem is simplified as a guard selection problem and guards, denning the discrete states, are derived using a simple circuit theoretical approach, by imposing certain regulation and control constraints. Satisfactory operation of the buck converter under the proposed scheme is demonstrated using computer simulations and laboratory experiments. The suitability and simplicity of the proposed control scheme over a wide range of disturbances is highlighted.     

An algorithm for spectral factorization using random search techniques

An approximation method for the energy spectrum of a stationary stochastic dynamical system is presented, which allows approximate functional rational factorization.This paper is in three parts. The first deals with a theoretical problem of approximation in Hardy Spaces, whose main result is the following:Let S⁽ⁱⁿ⁾, S be positive functions belonging to L¹(R_gw), such that log S⁽ⁿ⁾ and log S belong to L¹(R_ω, dω/1 + ω²).Let h⁽ⁿ⁾, h be the outer functions of the Hardy Space H²(Π₊) such that S^(g) = |h⁽ⁿ⁾|² and S = |h|² on iR.If S⁽ⁿ⁾ n^→∝ S in L¹(R_ω), and log S⁽ⁿ⁾ n^→∝ log S in L¹(R_ω, dω/1 + ω²), then: h⁽ⁿ⁾ n^→∝ h in H²(Π₊).The second part describes an effective algorithm, using random search methods, and gives an almost sure convergence result for it.The third part treats numerically two examples, permitting comparison of this algorithm with others (whenever there are…): the first example is a problem of approximation for a nonrational process (turbulence) that was considered in Ref. 22: the second example is a problem of model reduction (automatic) considered in Ref. 4.     

An integration-type high-speed analog-to-digital converter

An analog-to-digital (A/D) converter consisting of a switched-capacitor integrator, comparator, and control circuit is presented. The conversion process consists of voltage-to-frequency (V/F) conversion to determine the upper M bits of an N-bit representation of an analog input voltage and the subsequent voltage-to-time (V/T) conversion to determine the remaining lower N -M bits. The total clock cycle required for N-bit resolution is 2^M+2^N-M at most. The circuits for the V/F and V/T conversion share most of the components and thus the converter can be implemented with the minimum component count. Error analysis shows that a conversion accuracy higher than 12 bits can be expected from its CMOS monolithic realization. Prototype converters built using discrete components have confirmed the principles of operation     

基于多模型的自适应有源噪声控制算法研究

针对有源噪声控制中次级通道存在很大不确定性的问题，建立次级通道模型集以覆盖次级通道的不确定性，每个模型都有一个相对应的采用Modified FXLMS算法进行权值更新的自适应滤波器。在系统运行过程中，算法首先依据切换准则实时判断当前次级通道所处状态，选出最匹配的次级通道模型，同时把采用最匹配模型进行权值更新的自适应滤波器的参数复制给参与控制的滤波器。仿真和实验结果表明，采用多模型自适应的有源噪声控制算法提高了系统的鲁棒性。     

An averaging mode time-to-amplitude converter with picosecondresolution

A time-to-amplitude converter (TAC) meant to be employed in pulsed time-of-flight (TOF) laser rangefinding and capable of operating at a very high pulse repetition rate (PRR) is described. It is based on a precise time interval between the emitted light pulses and measures the phase difference of the logic-level pulse trains formed by timing pulses derived from the transmitted and received light pulses. The fast part of the TAC is constructed by means of ECL 100 K circuits. Test results indicate that the TAC is well suited for fast, millimeter-level resolution applications, and a full width at half maximum (FWHM) resolution of 1.0 ps is achieved with a 5-MHz pulse repetition rate and 0.1-Hz-10-kHz measurement bandwidth     

High-frequency link symmetrical active edge resonant snubbers-assisted ZCS-PWM DC?DC converter

A novel symmetrical zero current switching (ZCS)-pulse width modulation (PWM) cells-assisted high-frequency transformer link DC-DC converter using insulated gate bipolar transistor (IGBT) modules is presented. The proposed soft switching scheme is based on the switched-capacitor and inductive snubber in the high-voltage side inverter, assisted by active switching of MOSFET synchronous rectifier in the secondary-side low-voltage converter stage. By introducing the ZCS-PWM snubber cells, soft switching commutation which is less sensitive to the current level through the IGBTs can be achieved under the wide output power ranges. The converter circuit topology and the ZCS snubber cell operation are examined and evaluated with simulation results, and the feasibility of the converter topology is verified by experiments using a 1.0 kW-25 kHz prototype system.     

主动声纳检测技术的回顾与展望

由于低噪声隐身型潜艇的出现,声纳技术面临着激烈的挑战,低频主动声纳及其信号检测技术成为水声领域的研究热点之一。但是浅海的工作环境对主动探测相当不利,如何利用信道和背景干扰的特点,改进检测性能是研究的重点。模基处理、广义匹配滤波、混响消除、组合信号和波形融合处理、DLCT一体化处理等等技术在不同的方面能发挥一定的改进作用。对这些主动声纳检测技术的回顾与梳理,将为开展该领域研究工作提供一些有益的参考。随着人们对海洋环境理解的深入以及更准确、稳健性更好的水声模型建立,各种模基检测算法将被逐步应用到工程中。在此之前,诸如RCI/SRC这类介于模基和非模基之间的检测方法,由于其具有良好的稳健性、可移植性以及优于常规检测方法等优点,有望率先在工程中获得应用。同时,这些方法的组合应用,比如组合信号与波形融合、SRC/RCI相结合等,也就有较强的现实可操作性。     

Battery impedance spectroscopy using bidirectional grid connected converter

Battery impedance can provide valuable insight into the condition of the battery. Commercially available impedance measurement instruments are expensive. Hence their direct use in a battery management system is not justifiable. In this work, a 3-kW bi-directional converter for charging and discharging a battery bank has been implemented with the capability of impedance measurement. The converter is grid connected and controlled to operate at unity power factor. Additional requirements on filter design and control structure of battery converter for impedance measurement are discussed. An algorithm has been developed to measure impedance by frequency sweep, avoiding transients. The measured impedance has been compared to that from a commercially available impedance measurement equipment and is shown to have a good match.     

An eight-channel time-to-digital converter on a VME board

An eight-channel time-to-digital converter in a one-slot VME module has been developed. It is based on eight TAC sections and a 1 μs conversion time ADC unit with 12 bit resolution. Start and Stop input signals can be either NIM or ECL pulses and the Common-Start mode is available. The full-scale time range can be on-board selected between four values from 100 to 800 ns. The integral nonlinearity is less than ±0.04% for all ranges. The Low and High thresholds of any channel and other functions can be remotely controlled.     

转炉污泥吸附性能研究

Converter sludge, a byproduct produced on large amounts in the steel making process, is an important resource that can be utilized effectively. This paper describes an experiment in which converter sludge was tested as an adsorbent for the removal of phosphorus from waste water. It was found that the phosphorus removal depended on the amount of converter sludge added, the pH value and the contact time. Under laboratory conditions when the added sludge was 2. 0mg/100ml, the contact time 4h and the pH value of equalized 4, over 88% of phosphorus was removed; the experimental data on converter sludge adsorption of phosphorus in the water fitted the Freundlich isotherm model. Converter sludge was found to be very effective in adsorbing the phosphorus.     

An in vitro study of electrically active hydroxyapatite-barium titanate ceramics using Saos-2 cells

Electrically active ceramics are of interest as bone graft substitute materials. This study investigated the ferroelectric properties of hydroxyapatite-barium titanate (HABT) composites and the behaviour of osteoblast-like cells seeded on their surfaces. A piezoelectric coefficient (d₃₃) of 57.8 pCN⁻¹ was observed in HABT discs prepared for cell culture. The attachment, proliferation, viability, morphology and metabolic activity of cells cultured on unpoled HABT were comparable to those observed on commercially available hydroxyapatite at all time points. No indication of the cytotoxicity of HABT was detected. At one day after seeding, cell attachment was modified on both the positive and negative surfaces of poled HABT. After longer incubations, all parameters observed were comparable on poled and unpoled ceramics. The results indicate that HABT ceramics are biocompatible in the short term in vitro and that further investigation of cell responses to these materials under mechanical load and at longer incubation times is warranted.     

An active millimeter load-pull measurement system using twosix-port reflectometers operating in the W-frequency band

An active load-pull measurement system using two six-port reflectometers operating in the W-frequency band is demonstrated. Ninety loads over the whole Smith chart have been synthesized and measured by both reflectometers. The maximum deviation between both measurement data is 0.02 for the magnitude and 3° for the phase of the reflection coefficient of the 90 loads. The constant power gain circles of a PHEMT operating at 89 GHz are shown and compared with those calculated from its S_ij scattering parameters. The deviation between the radii of circles is less than 0.03     

Development of a fast neutron radiography converter using wavelength-shifting fibers

A fluorescent converter for fast neutron radiography (FNR) comprising a scintillator and hydrogen-rich resin has been developed and applied to electronic imaging. The rate of the reaction between fast neutrons and the converter is increased by thickening the converter, but its opaqueness attenuates emitted light photons before they reach its surface. To improve the luminosity of a fluorescent converter for FNR, a novel type of converter was designed in which wavelength-shifting fibers were adopted to transport radiated light to the observation end face. The performance of the converter was compared with that of a polypropylene-based fluorescent converter in an experiment conducted at the fast-neutron-source reactor YAYOI in the University of Tokyo.     

Dc-to-Dc converter using inductive-energy storage for voltage transformation and regulation

A nondissipatively regulated dc-to-dc converter that operates very efficiently at high frequencies is presented. The circuit is characterized by a small number of power handling components, many of which perform multiple duties. Only one power transistor is used, and the characteristics of the main power handling magnetic element of the circuit are such that this element is not only able to provide voltage transformation but also to perform certain filtering functions which in conventional converters normally require a separate filter inductor. Two different methods of nondissipative closed-loop regulation are presented-one involving control of the duty cycle of the power switch, and the other involving magnetic-amplifier control of the average output current. Certain design considerations are presented, and a test circuit is described.     

Optical-fiber finger photo-plethysmograph using digital techniques

This paper presents digital techniques to design an optical-fiber photo-plethysmograph. This noninvasive method is based on the measurement of the intensity of an infrared-light beam, which penetrates the index finger. Sinusoidal modulation of the light-beam by driving an infrared LED is proposed. The method of direct digital synthesis is used to produce a very stable sinusoidal waveform. Optical fibers are used to transfer the light to and from the sampling point. Synchronous amplitude demodulation is used here instead of using analog low-pass filters, so the information concerning the amplitude is almost noiseless. Off-line frequency analysis of the peripheral volume pulse-wave signal is performed. The power content in the harmonics of this pulse wave may be a useful measure of aging and vascular disease