一种基于时间寄存型脉宽比较器和离散时间微分器的无采样时钟准数字FSK解调器

本文提出并实现了一种高载波频偏抑制、无采样时钟的准数字频移键控(FSK)解调器。解调器采用了一种对工艺、温度和电压等变化具有较好鲁棒性的准数字时间寄存器构造成脉宽比较器,无需高频采样时钟便可对FSK信号的载波周期进行精确鉴别从而实现信号的解调。同时在解调器中集成了一种离散时间微分器,可有效地抑制FSK信号载波频率偏差和漂移对解调性能的影响。本文完成了解调器的原型设计、原理分析、制作和测试。测试结果显示解调器只需最低10.7 dB的信噪比,便可对调频系数0.5、数据率1 Mpbs的FSK信号实现解调(误码率不超过10^-3),同时能够对-0.56～0.48 MHz范围内变化的载波频偏和频漂进行有效抑制。     

Digital, synchronously timed control system for pulsed ion cyclotron resonance mass spectrometry

An integrated control system for a pulsed ion cyclotron resonance (ICR) mass spectrometer has been designed, constructed, and put into operation. It utilizes a crystal clock oscillator to accurately control the delay and width of the various pulses necessary for pulsed ICR operation. A switched integrator, sample/hold postdetection system is also described which improves aquisition, display, and signal-to-noise characteristics of the detected ion signal obtained from a gated marginal oscillator detector.     

Measurement of ac cataphoresis

An apparatus and techniques are described for measurements of ac cataphoresis. The system uses a fiber optics light pipe driven along the discharge tube axis by a synchronous clock drive system. The collimated light signal is directed to a spectrometer whose output is processed using various methods to obtain desired types of information, including longitudinal time averaged scans of the discharge tube, longitudinal gated scans, and gated single cycle observations. Using these techniques one is able to study the time development of the ac effect as well as the presence of ionization waves. Examples are shown using noble gas mixtures of the various sampling procedures.     

Quasi-optical diplexer for millimeter wavelengths

A quasi-optical diplexer for injection of signal and local oscillator frequencies into a mixer at millimeter wave-lengths is described. The diplexer accepts both image and signal bands, presents low loss at both the signal and local oscillator frequencies and rejects local oscillator noise at the signal frequency. The configuration of the device makes it particularly useful for Cassegrain receivers using a cooled mixer and a lens corrected feed system. The diplexer has been tested at 150 GHz on the 11-m radio telescope operated by The National Radio Astronomy Observatory in Tucson, Arizona.     

Free spectral range measurement of fabry-perot cavity using frequency modulation

In this paper, we propose a novel method to measure the free spectral range (FSR) of a Fabry-Perot cavity (FPC) using single-frequency modulation (FM) with one electric optical modulator (EOM) and the null method. A laser beam modulated by the EOM, to which a cosine-wave signal is supplied from a radio frequency (RF) oscillator, is incident on the FPC. The transmission light from the FPC is observed and converted to an RF signal by a highspeed photodetector, and the RF signal is synchronously demodulated with a lock-in amplifier (LIA) by referring to the oscillator. We theoretically and experimentally demonstrate that the LIA signal become null with a steep slope, when the modulation frequency equals the FSR under the condition that the carrier frequency is slightly detuned from the resonance of the FPC. The experimental results show that the proposed method has the capability to determine the FSR by the null method with a small measurement uncertainty.     

Calibration of the scintillation trigger detector of the forward muon system for the D0 experiment

A procedure for LED-based calibration of the scintillation trigger detector of the forward muon system for the D0 experiment on the Tevatron collider at the Fermi National Accelerator Laboratory (Batavia, United States) is presented. During its 4-year operation, the deviation in the signal amplitudes averaged over 4214 counters was 4% or less and the variance (σ) of the distribution of these deviations over all counters was 10%. In the same period of time, the signals remained stable in time with an accuracy of 0.23 ns and the variance (σ) of the distribution of these deviations was 0.52 ns. The calibration procedure based on measuring the amplitude response of the detector counters to muons produced by proton-antiproton collisions at the Tevatron collider is also described. The variations in the absolute value of the amplitude responses over a period of 4 years were in the range of +3%...?9%.     

A two-channel radiometer based on the null measurement method

A two-channel microwave radiometer (with two receivers) for the decimeter wavelength range is described. The null measurement method is realized in this instrument through application of combined pulse (amplitude and pulse-width) modulation. The use of a special algorithm for forming signals controlling the pulse-width modulation in each channel reduces the dynamic errors in tracking the changes in the antenna signal.     

A highly-sensitive weak-signal complex-amplitude meter

A measuring section of a multifrequency electromagnetic ground-probing device operating at discrete frequencies in a range of 2.5–250 kHz is described. The measuring section of the device contains a lownoise amplifier, complex-signal demodulator, and integrators based on δ-σ analog-to-digital converters. The following characteristics of the device are attained: the root-mean-square noise is 20 nV, the measurement range is ±500 μ V, the number of bit is 20, the measurement time is 80 ms, and the power-line noise suppression at 48–52 Hz is more than 120 dB.     

单颗粒质谱数据采集系统动态范围的扩大

大气气溶胶单颗粒物的化学组分复杂,含量差异较大,单颗粒气溶胶质谱仪利用激光电离颗粒物会产生大量幅值差异较大的离子信号,常规的数据采集系统不足以准确检测其质谱信息。本研究开发了一套新的数据采集系统,采用高、低量程叠加采样法分别单独检测大、小信号,并通过一定的算法合并信号,有效地扩大了质谱检测系统的动态范围。该方法不仅能够真实地还原谱图的原始信息,还可以提高质谱识别颗粒物的准确率以及颗粒的利用率。     

Frequency-following reference oscillator for a two-phase lock-in amplifier

The circuit for a frequency-following oscillator is described for use in obtaining a commensurate reference for a two-phase lock-in amplifier. This device is useful in tracking signals which drift slowly in frequency and which are apt to be either intermittent or momentarily small in amplitude, as in the Brownian motion of a mechanical oscillator. Digital hysteresis is used to reduce the number of tracking corrections made when the signal and the reference oscillator are close in frequency and to increase the number of corrections when they are not.     

The Calibration Telescope System of the NEVOD Cherenkov Water Detector

The calibration telescope system of the NEVOD Cherenkov water detector is described. Scintillation counters are used in the setup as detecting elements. The detection system is equipped with logical and amplitude channels and provides the calibration of the Cherenkov water detector. It can also be used to investigate the electron and muon components of an extensive air shower. A method for amplitude calibration of the scintillation counters is described, with which it is possible to estimate the number of detected charged particles. The results for the 1.5-year operation of the setup as a detector of extensive air showers are presented.     

Base-line suppression in microwave spectroscopy using frequency modulation and harmonic detection

In a microwave spectrometer, systematic variations of the rf source amplitude with frequency can cause a spurious signal (base line) which severely limits the attainable sensitivity. Normally, the base line is eliminated by using Stark or Zeeman modulation. However, these modulation methods cannot be used in an experiment on nonparamagnetic molecular ions contained in a glow discharge. This paper discusses a technique which we have used to reduce the base line by a factor of about 10(-5) and which can be used to study the spectra of species contained in a glow discharge. The scheme uses wideband sinusoidal frequency modulation of the microwave source combined with synchronous detection at the nth harmonic of the modulation frequency. The system produces a signal proportional to the nth derivative with respect to frequency of the base line. However, the signal due to an absorption line is only slightly smaller than that produced by other modulation methods. The system may be considered to behave like a high-pass filter which discriminates against features that vary slowly with frequency.     

定张力杜瓦布线仪研制

一种制造多电极杜瓦瓶用的固定张力布线仪已研制成功,这种杜瓦瓶是红外焦平面成像探测所必需的。采用了一种特制的半导体应变传感器,0～500g 范围内灵敏度0.23m V/g.步进电机拖动。平衡点判断利用了门电路的临界特性。V-F起振电压及频率均经最佳化。系统启动后的控制仅用一只脚踏开关。实际系统张力误差在范围10～500g 间小于1g.步进电机步长小于0.15mm.布线机适于线数不大于180,长度不大于200mm.     

一种用于电机铁芯磁性能测试的恒流源

针对电机铁芯磁性能测试中保持磁场强度H的波形为正弦形的问题,设计了一种基于数字信号处理器(DSP)全数字实时控制的逆变恒流源。分析了正弦波逆变电源斩波和逆变控制的一般方法和特点,控制系统前级采用同步Buck电路对母线电压斩波,斩波输出电压经过PI闭环控制实现了其在突加、突减负载时的稳定性。控制系统后级通过对电感电流的PID闭环控制和单极性正弦脉宽调制(SPWM)方式,实现瞬时跟踪给定的交流恒流源控制。实验结果表明逆变恒流源具有很好的静、动态性能和稳定性,输出信号谐波含量少,负载适应能力强,很好地实现了系统设计的要求。     

Dynamic properties of measuring circuits applied to frequency output transducers

Frequency output measuring transducers transform the measured quantity x into the frequency f or the period T of the output signal. Frequency is usually measured by counting the number of pulses produced by the output voltage during a constant counting time t_c, long enough to minimize a random error. The period is measured by counting the pulses of a reference oscillator in the varying time equal to N periods of the transducer's output signal. Considering the dynamic properties of both measuring chains one may conclude that averaging of the measured occurs, and in order to calculate the dynamic error, an averaging transducer ought to be taken as a reference. The paper indicates that under dynamic conditions the frequency measuring chain may be treated as a really averaging one, the period measuring chain only as an approximately averaging one, and in both cases averaging is not sufficient to eliminate the aliasing error of the sampling procedure. A method for accelerating the measurement and then avoiding the aliasing error is the “one-period method” considered in the paper. The averaging error and delay error of this method are considered in detail, under the assumption that a parameter-controlled oscillator is used as an element of the measuring chain.     

A fiber-optic-link-based analog-signal transmission system for the diagnostics of nanosecond processes

The design and results of studies of a fiber-optic-link-based transmission system for transmitting analog signals of nanosecond duration using an external modulation of radiation are presented. Experimental studies that were performed at the Dukhov All-Russia Research Institute of Automatics demonstrated a method for determining the transmission function of an intensity modulator, which is based on the Mach–Zehnder interferometer, simultaneously with the signal transmission. The dynamic range of the system with one intensity modulator is ~70 when recording a single-shot process. The dynamic range of the transmission system with two modulators that form two information channels exceeds 200 with a bandwidth that exceeds 4 GHz and a signal-to-noise ratio of at least 5 for the minimum recorded signal.     

Note: Phase-locked loop with a voltage controlled oscillator based on a liquid crystal cell as variable capacitance

A phase-locked loop is demonstrated using a twisted-nematic liquid crystal cell as a capacitance that can be varied as a function of applied voltage. The system is formed by a phase detector, a low-pass filter, as well as a voltage controlled oscillator including such variable capacitance. A theoretical study is proposed and experimentally validated. Capture and locked ranges of hundreds of kHz have been obtained for the configuration used in this circuit. An application as frequency demodulator using a practical implementation of this circuit has been demonstrated.     

发动机激励下行星传动非线性啮合力特性

建立了发动机波动转矩激励下的行星传动纯扭非线性振动模型,模型中考虑了齿侧间隙、时变啮合刚度及其相位差、综合啮合误差以及各行星轮位置相角时变性。根据信号调制原理,分析了行星排啮合力边频带的产生原因。把发动机转速、转矩分成4种典型工况,在时域和频域内对行星排啮合力进行深入分析。研究表明,啮合力以单边冲击为主,啮频倍频与部件转频倍频调制普遍存在,受发动机工作状态影响相对较小,啮频倍频与波动转矩频率倍频调制则受工作状态影响很大,高速重载时作用最显著。该结论为行星齿轮传动设计提供了依据。     

Ultrafast photon counting applied to resonant scanning STED microscopy

To take full advantage of fast resonant scanning in super‐resolution stimulated emission depletion (STED) microscopy, we have developed an ultrafast photon counting system based on a multigiga sample per second analogue‐to‐digital conversion chip that delivers an unprecedented 450 MHz pixel clock (2.2 ns pixel dwell time in each scan). The system achieves a large field of view (～50 × 50 μm) with fast scanning that reduces photobleaching, and advances the time‐gated continuous wave STED technology to the usage of resonant scanning with hardware‐based time‐gating. The assembled system provides superb signal‐to‐noise ratio and highly linear quantification of light that result in superior image quality. Also, the system design allows great flexibility in processing photon signals to further improve the dynamic range. In conclusion, we have constructed a frontier photon counting image acquisition system with ultrafast readout rate, excellent counting linearity, and with the capacity of realizing resonant‐scanning continuous wave STED microscopy with online time‐gated detection.     

基于强度-相位级联调制的微波光子下变频法

为了优化微波光子下变频的无杂散动态范围,结合带反馈控制的强度调制器和相位调制器,提出并验证了基于强度和相位级联调制的微波光子下变频方法。通过理论推导和仿真分析了下变频原理以及本振功率对系统性能的影响,搭建了强度-相位级联调制的微波光子下变频系统,利用自行研制的直流偏置反馈控制模块确保强度调制器的工作状态稳定,对系统进行了性能测试。实验结果表明,增益和无杂散动态范围分别为-6.65dB和108.62dB/Hz~(2/3),与传统的强度调制器级联下变频链路相比,增益和无杂散动态范围分别提高了3.56dB和19.87dB。基于强度和相位级联调制的下变频方法仅需要单个偏置电压,且可通过反馈模块实现工作状态的稳定控制,系统结构简单、性能稳定,可实现大动态范围的微波光子下变频。