具有随机特征频率和延迟核函数的分数阶线性振荡器中的随机共振

研究了具有延迟核函数和随机特征频率的分数阶线性振荡器中的随机共振(stochastic resonance,SR)现象。基于线性系统理论,利用拉普拉斯变换,推导出了分数维振荡器系统输出幅度(system output amplitude,SOA)的解析表达式。分析表明,SOA是核函数延迟时间的周期函数。在SOA与噪声相关率、噪声幅值、分数维数的关系曲线上都发现了随机共振现象。分析了SOA与系统参数及噪声稳态概率间的非单调依赖行为。     

The new design of AGC circuit for the sinusoidal oscillator with wide oscillation frequency range

The typical automatic gain control (AGC) schemes are not suitable for the sinusoidal oscillator with wide oscillation frequency range. To solve this problem, the up-down counter, multiplying digital-to-analog converter, and high-speed comparators are employed to achieve the proposed AGC circuit, which corrects the complex roots of the overall system automatically to the imaginary axis of the complex frequency plane. The negative feedback technique with digital hardware is applied on the loop gain control. No low-pass filter is needed to detect the oscillation amplitude. Thus, this technique is suitable for the sinusoidal oscillator with wide oscillation frequency range. The oscillation frequencies ranging from 7 Hz to 1 MHz are tested with the proposed AGC circuit. The experimental results demonstrate the static characteristics and dynamic responses of the overall system.     

分数阶单自由度间隙振子的受迫振动

研究了含有分数阶微分项的单自由度间隙振子的受迫振动,利用KBM渐近法获得了系统的近似解析解。分析了分段线性系统的主共振,得到了分数阶阶次在0～2时分数阶项的统一表达式;发现分数阶微分项在分段系统中以等效线性阻尼和等效线性刚度的形式影响着系统的动力学特性,而间隙以等效非线性刚度的形式影响着系统的动力学特性。获得了主共振幅频响应的表达式,并得到了系统的稳定性条件;比较了系统主共振幅频响应的近似解析解和数值解,发现两者符合程度较高,验证了近似解析解的正确性;详细分析了分数阶项和间隙对系统主共振幅频响应的影响。研究表明KBM渐近法是分析分数阶分段光滑系统动力学的有效方法。     

Oscillators with Frequency and Amplitude Outputs for the Measurement of Two Parameters

A class of harmonic oscillators is described which has the frequency of oscillation determined by one parameter of an RC or RL circuit and the amplitude of oscillation by the other parameter. These oscillators are useful in the impedance measurement of physical or biological objects when two attributes of the object are related to two electrical parameters of the equivalent circuit. A pole or zero is derived from the measured object by isolating it from the oscillator. The remainder of the oscillator contains linear elements and a single memoryless nonlinearity. Second-order oscillators containing a hard nonlinearity and third-order oscillators containing a soft nonlinearity are presented. The frequency and amplitude relationships are derived using linear theory and the describing function method. The theoretical results are verified by analog computer simulations. The oscillators are described in general terms by means of flow graphs.     

达芬-谐波振子的改进解析逼近解

研究达芬-谐波振子的解析逼近解。所谓达芬-谐波振子是指当位移远小于1时，系统可化为三次非线性振子，而当位移远大于1时，该系统则化为线性谐波振子。通过将变形后的控制方程的线性化与谐波平衡法组合起来，我们建立了达芬-谐波振子频率及周期解的改进解板逼近。改进的解析逼近在振幅的全部取值范围内，包括振幅趋于零及无穷的情况，都有令人非常满意的精度。     

电调频率多相正弦波振荡器

本文论述采用跨导型运算放大器构成的多相正弦波振荡器．这种振荡器可提供n个幅度相等、相位等间隔分布的信号，振荡频率正比于跨导型运放的跨导，通过改变偏置电流可电调振荡器频率．     

Modeling of quartz crystal oscillators by using nonlinear dipolar method

A quartz crystal oscillator can be thought of as a resonator connected across an amplifier considered as a nonlinear dipole the impedance of which depends on the amplitude of the current that flows through it. The nonlinear amplifier resistance and reactance are obtained by using a time domain electrical simulator like SPICE (Simulation Program with Integrated Circuit Emphasis): the resonator is replaced with a sinusoidal current source of the same frequency and a set of transient analyses is performed by giving the current source a larger amplitude. A Fourier analysis of the steady-state voltage across the dipolar amplifier is performed to calculate both real and imaginary parts of the dipolar impedance as a function of the current amplitude. From these curves, it is then possible to accurately calculate the oscillation amplitude and frequency without having to perform unacceptably long transient analyses needed by a direct oscillator closed loop simulation. This method implemented in the Analyse Dipolaire des Oscillateurs a Quartz or Quartz Crystal Oscillators Dipolar Analysis (ADOQ) program calculates the oscillation start-up condition, the oscillation steady-state features (oscillation amplitude and frequency), and the oscillator sensitivity to various parameters. The oscillation nonlinear differential equation is solved by using the slowly varying function method so that the program quickly and accurately calculates the current amplitude and frequency transients. Measurements performed on an actual amplifier show a very good agreement with the results obtained by the simulation program.     

An ultra low cost and miniature 950–2050 MHz GaAs MMIC downconverter‐I: Design approach and simulation

Abstract

A miniature ultra low cost 950–2050 MHz GaAs MMIC downconverter has been designed for satellite TV application using a 1‐μm gate‐length, ion‐implanted GaAs MESFET foundry process. To accurately predict circuit performances, both linear and nonlinear equivalent circuit models have been developed to characterize the RF and dc behaviors of device. Modeled simulation results show correspondence with the experimental data. This monolithic downconverter is comprised of an RF LNA, a dual‐gate MESFET mixer, an IF variable gain amplifier, and a varactor tuned oscillator. The primary design specifications are (1) 50‐dB conversion gain, (2) 4‐dB noise figure, (3) more than 40‐dB gain controllable range, and (4) 50‐dBc third‐order intermodulation distortion. The chip size is 1.4 × 1.5 × 0.18 mm³. It is encapsulated in a standard low cost plastic package. Moreover, this downconverter IC is promising for miniaturization and cost‐reduction of a DBS receiver. The detailed measured characteristics will be presented in part‐II of this paper.     

New ADC with piecewise linear characteristic: casestudy-implementation of a smart humidity sensor

In this paper, the architecture of a new analog-to-digital converter (ADC) with a piecewise linear characteristic (PLADC) is proposed. In this device, some discrete points of the characteristic can be modified to fit a requested profile. This converter facility can be utilized to gain remarkable advantages in a wide variety of applications, such as the implementation of a sensor linearization technique. In the paper the internal architecture of a two-stage 11-b flash PLADC prototype is briefly described. A representative demonstrative application, namely, the implementation of a linear digital humidity sensor, is discussed showing the effectiveness and usefulness of this device. The problem of the characterization of this converter is also discussed, reporting some remarks about the implemented solutions     

含分数阶导数项的随机Duffing振子的稳态响应分析

本文对一个含有分数阶导数项阻尼的、Gaussian白噪声激励下的Duffing振子进行了稳态响应分析。首先,基于能量平衡理论,运用等效线性化方法,计算等效系统的线性阻尼及自然频率,建立统计意义下的等效线性化系统。然后,利用平均法建立随机Ito方程,得到随机响应的Markovian近似;给出描述振子振幅概率密度函数演化的Fokker-Planck方程,并得到它的稳态解。进一步,对于含有响应振幅的等效线性系统,借助由Laplace变换得到的转换函数,得到原系统的条件功率谱密度,结合振幅的稳态概率密度作为权重函数,给出原系统功率谱密度的估计,以及响应的统计量的估计。数值模拟的结果说明所提出的功率谱密度的近似解析表达式是可靠的,它甚至适用于Duffing振子具有强非线性回复力的情形,因为它可以较好的表现出功率谱密度共振频谱加宽及多峰现象的出现。     

Effective resistance of current-carrying superconducting wire in oscillating magnetic fields 2. Twisted multifilamentary composite conductor

The influence of oscillating magnetic fields of low frequency on the dc transport current in a twisted multifilamentary conductor has been studied by observing the terminal voltage of the conductor. An analysis of the voltage versus oscillating field characteristics, combined with theoretical considerations, shows that current distribution among the filaments becomes uniform due to the oscillation of the field, and an effective resistance appears in the transport current when the amplitude of the oscillating field exceeds a certain threshold value. The dependence of the effective resistance on the characteristic parameters of both the oscillating field and the filamentary conductor is clarified.     

Investigation of the Microphysical Characteristics of Aerosols by the Method of Electrodynamic Suspension of Particles. 1. Structure of the EDS and Determination of the Drag Force of Microparticles

This paper describes the structure of an electrodynamic suspension (EDS) with flat electrodes for investigating a complex of characteristics of charged microparticles and the surrounding gas. A linear theory of oscillatory motion of a microparticle in the EDS volume has been developed and analytical expressions for the oscillation amplitude and the center of oscillation of a particle depending on the electrode voltage value have been obtained. The stability boundary of motion of particles of various substances for the EDS of the given configuration has been determined theoretically. For the first time the dynamic behavior of aerosols in the EDS in a wide range of change in the surrounding gas pressure (Knudsen number) has been studied experimentally, in particular, data for the drag force of a particle have been obtained. Comparison between the experimental and theoretical data has been made.     

Optimal biasing of magnetoresistance amplifiers

The magnetoresistive amplifier is usually implemented by allowing an input signal current to modulate a magnetic field which, in turn, produces a change in the resistance of an active element in the output portion of the device. Amplifiers of this type may be classified either as a conventional type, which utilizes the normal magnetoresistive effect of the active material, or as a type which employs the characteristics of a superconducting element operating in the resistive transition region. In both cases, there has been reported experimental data which indicates that the power gain for these amplifiers is a function of the biasing magnetic field (or biasing current), and that an optimal value of the bias field exists which results in a maximum value of the power gain. Analytical methods of determining these optimal values are derived and theoretical predictions based on these methods are shown to be consistent with the experimental results.     

Voltage transformer based on inverse magnetoelectric effect

A voltage transformer, the operation of which is based on the inverse magnetoelectric effect, has been studied. The device comprises a nickel-PZT-nickel trilayer capacitor structure on which an induction coil is wound. It is established that the frequency dependence of the output signal has a resonance character and the transmission characteristic is linear in a broad range of input voltages.     

A prototype kinetic inductance thermometer for X-ray calorimetry

We have measured the parameters of a prototype kinetic inductance thermometer for X-ray calorimetry which was fabricated at GSFC. This device consists of an aluminum meander strip and ground plane and operates at about 1.2 K. For thermal isolation, the device was suspended on Kevlar threads along with a heater and a germanium resistance thermometer. The meander strip was included in the tank circuit of a 10 MHz tunnel diode oscillator operating at about 1 K. The kinetic inductance was measured by monitoring the oscillator frequency. The temperature dependence of the kinetic inductance was found to be in reasonable agreement with the behavior predicted from the device parameters. Having characterized this proof-of-concept device, we intend to investigate the suitability of kinetic inductors operating at lower temperatures for X-ray calorimetry.     

Analysis and design of negative resistance oscillators using surface transverse wave-based single port resonators

This practically oriented paper presents the fundamentals for analysis, optimization, and design of negative resistance oscillators (NRO) stabilized with surface transverse wave (STW)-based single-port resonators (SPR). Data on a variety of high-Q, low-loss SPR devices in the 900- to 2000-MHz range, suitable for NRO applications, are presented, and a simple method for SPR parameter extraction through Pi-circuit measurements is outlined. Negative resistance analysis, based on S-parameter data of the active device, is performed on a tuned-base, grounded collector transistor NRO, known for its good stability and tuning at microwave frequencies. By adding a SPR in the emitter network, the static transducer capacitance is absorbed by the circuit and is used to generate negative resistance only over the narrow bandwidth of the acoustic device, eliminating the risk of spurious oscillations. The analysis allows exact prediction of the oscillation frequency, tuning range, loaded Q, and excess gain. Simulation and experimental data on a 915-MHz fixed-frequency NRO and a wide tuning range, voltage-controlled STW oscillator, built and tested experimentally, are presented. Practical design aspects including the choice of transistor, negative feedback circuits, load coupling, and operation at the highest phase slope for minimum phase noise are discussed.     

Double-resonance quartz crystal oscillator and excitation of a resonator immersed in liquid media

In this work we propose a novel circuit design: a double-resonance oscillator. Its oscillation shows two oscillation modes: frequency locking to the quartz crystal resonance and LC resonance oscillation. Transition of the oscillation mode and the strength of oscillation are analyzed and reviewed for the fundamental mode in comparison with a Colpitts oscillator. The experimental results support the estimates of negative resistance for the double-resonance oscillator compared with the LC oscillator.     

Flat coil-based tunnel diode oscillator enabling to detect the real shape of the superconductive transition curve and capable of imaging the properties of HTSC films with high spatial resolution

Owing to a pick-up coil's flat design, relatively low MHz-range operation frequency, and six orders relative resolution a flat coil-based tunnel diode oscillator has advantages, compared to all other methods. They become crucial in studies with thin high-T_c superconductivity (HTSC) materials (with small signals), especially at the start of the Cooper pairs’ formation. Due to this the superconductivity precursor ‘paramagnetic’ effect was detected recently in YBaCuO films at N/S transition. It precedes Meissner ejection and specifies details of the shape of the transition curve. We discuss the influence of the currents on this effect, and the relationship between the quality of the material and the shape of the effect. A new imaging device has also been created based on this test method (using a focused He–Ne laser beam as a probing signal), capable of imaging the properties of HTSC films with 3 μm spatial resolution. The method is based on detection of the inductance and Q-factor value changes of a single-layer flat coil, placed at the face of the sample. This leads to frequency and/or amplitude changes of the stable oscillator. The test device enabled 2D-mapping of the grain structure of a bridge-shaped YBaCuO film. Basically, the method is capable of imaging 2D-current distribution in thin HTS with sub-μm spatial-resolution, using non-bolometric response. However, the achieved resolution 3 μm of a bolometric nature (in a given device with 3.5 mm-size coil) by no means is limited by the abilities of the method, but mainly, it depends on how narrowly it is possible to focus the probing beam, while the own resolution of a present flat coil-based technique is better than 0.1 μm, and can be improved essentially by reducing the coil size.