A Frequency-Lock System for Improved Quartz Crystal Oscillator Performance

The intrinsic noise of the best quartz crystal resonators is significantly less than the noise observed in oscillators employing these resonators Several problem areas common to traditional designs are pointed out and a new approach is suggested for their solution. Two circuits are described which frequency lock a spectrally pure quartz crystal oscillator to an independent quartz crystal resonator. The performance of the composite system is predicted based on the measured performance of its components.     

晶振电极激光减薄调频技术的研究

石英晶振的谐振频率在出厂前都需要进行微调,使之达到需要的标称值。本文提出激光调频的新技术,利用适当激光能量使电极膜层汽化减薄,从而使晶振的频率精确升高到预期值,重点研究了激光器的工作电流和Q脉冲宽度等参数对晶振频率微调的影响。实验结果表明:当工作电流太小(10A)或Q脉冲宽度太大(10μs)时,激光脉冲的峰值能量密度太小不足以有效实现频率微调;当工作电流和Q脉冲宽度比较合适(电流约为11A,Q脉冲宽度为4～10μs)时,石英晶振的谐振频率可以被线性地调节,此时对晶振其它电性能参数影响很小;当工作电流过大(11A)或Q脉冲宽度过小(4μs)时,激光脉冲能量密度过大,很容易对电极膜造成损伤而导致不能起振。     

Frequency Stability Analysis of Transistorized Crystal Oscillator

This paper gives an analysis of a modified Pierce oscillator for frequency variation due to changes in the circuit or transistor. The magnitudes of the frequency shifts due to parameter changes are computed in relation to each other. The analysis has been verified by testing the oscillator circuit with several transistors which had significantly different measured parameters. Computed frequency shifts were compared with measured frequency shifts. The agreement between experimental and calculated data is ?8×10-9 with a 5 Mc, fifth overtone quartz crystal in the circuit. A general equation relating frequency changes to changes in circuit parameters has been derived and is applicable to any operating frequency as long as the y parameters of the transistor and the circuit elements of the oscillator are known.     

石英晶体振荡器日频率波动的测量及不确定度分析

本文介绍了电子测量仪器内石英晶体振荡器的日频率波动的测量方法并分析了测量值的不确定度。     

Measurement of the Short-Term Stability of Quartz Crystal Resonators and the Implications for Crystal Oscillator Design and Applications

A new technique is presented which makes it possible to measure the inherent short-term stability of quartz crystal resonators in a passive circuit. Comparisons with stability measurements made on crystal controlled oscillators indicate that noise in the electronics of the oscillators very seriously degrades the inherent stability of the quartz resonators for times less than 1 s. A simple model appears to describe the noise mechanism in crystal controlled oscillators and points the way to design changes which should improve their short-term stability by two orders of magnitude. Calculations are outlined which show that with this improved short-term stability it should be feasible to multiply a crystal controlled source to 1 THz and obtain a linewidth of less than 1 Hz. In many cases, this improved short-term stability should also permit a factor of 100 reduction in the length of time necessary to achieve a given level of accuracy in frequency measurements.     

无晶振频率输出测时仪的一种检定方法

本文介绍了测时仪无晶振频率输出，又无电信号输入时，采用按键开关，直流稳压电源，使纳秒通用计数／计时器与被检测时仪同步来检定其内部晶振指标的方法，并对其不确定度进行了分析。     

石英晶体元件负载谐振频率测量技术的研究

在分析与对比三种测量石英晶体元件负载谐振频率方法的基础上,设计适用于测量法的π网络与整个测量系统,采用自动网络分析仪测量晶体的阻抗,采用测量法测出负载谐振频率.实验表明,在1 MHz～200MHz频率范围内,系统对负载谐振频率重复测量一致性能达到士1×10-6以内,在30 MHz～200MHz频段,测量误差达到士2×10-6以内.     

晶体振荡器1s频率稳定度的测量及不确定度分析

本文介绍了电子测量仪器内石英晶体振荡的1s频率稳定度的测量方法并分析了测量值的不确定度。     

Quartz Crystal Parameters Measurement System

A device for measurement of quartz crystal resonator parameters is presented. This device is using a synthesizer, the frequency of which is swept step by step to find the resonance of the crystal. With a phase loop, which controls the synthesizer's interpolator, the resonance frequency and the bandwidth of the crystal can be measured. A low-cost computer gives the values of the resistance and the Q factor. The time constants of the crystal and of the phase loop are studied to determine the best measurement speed of this automatic device.     

A Synchronous Sweep Frequency Oscillator

This paper describes a linear frequency sweep oscillator which is accurately controlled by a master clock. The voltage controlled oscillator which generates the frequency sweep is first phase-locked to the master clock. Then, a ramp generator drives the voltage controlled oscillator over the required frequency range, while a phase-sampling loop controls the instantaneous frequency to the desired ramp accuracy. The phase-sampling control loop is synchronized to the master oscillator by the sampling rate, which is derived directly from the master clock frequency. A laboratory system constructed on these principles sweeps from 2.095 MHz to 2.320 MHz in approximately 1.709 seconds, with a deviation from linearity of less than ±75 Hz.     

爆破冲击性低频噪声特性及其控制研究

工程爆破中产生的噪声直接影响施工人员的身心健康和周围环境安全.为研究和控制爆破噪声,通过爆破实验对噪声进行了现场测试,并对测试结果进行了分析.研究表明,爆破噪声的危害主要是由其低频部分(7～59 Hz)引起的.在全面分析爆破冲击性低频噪声特性的同时,结合上海宝钢集团第一钢厂聚能切割爆破的具体情况,提出了爆破噪声控制的工程技术手段,为控制爆破噪声提供科学和实践依据.     

Frequency Multiplication Effects on Oscillator Instability

The effects which frequency multiplication produces on the power spectral density of an oscillator is examined as a function of the multiplication ratio and the power spectral density of the phase noise process. In addition, the power spectral density (PSD) of the multiplied-up oscillation is interconnected with the frequency standard L(f). It is explicitly demonstrated how errors are introduced when one attempts to define the rms fractional frequency deviation ?f(?)/f0 and the Allan variance ?2y(?) using the measurement of L(f). Finally, the genesis of spectral spreading of the PSD due to frequency multiplication is demonstrated in such a way that this interesting and important phenomena can be grasped by the practicing engineer.     

Low Frequency Elastic Measurements on Solid ^{4}He in Vycor Using a Torsional Oscillator

Torsional oscillator (TO) experiments involving solid \(^{4}\) He confined in the nanoscale pores of Vycor glass showed anomalous frequency changes at temperatures below 200 mK. These were initially attributed to decoupling of some of the helium’s mass from the oscillator, the expected signature of a supersolid. However, these and similar anomalous effects seen with bulk \(^{4}\) He now appear to be artifacts arising from large shear modulus changes when mobile dislocations are pinned by \(^{3}\) He impurities. We have used a TO technique to directly measure the shear modulus of the solid \(^{4}\) He/Vycor system at a frequency (1.2 kHz) comparable to that used in previous TO experiments. The shear modulus increases gradually as the TO is cooled from 1 K to 20 mK. We attribute the gradual modulus change to the freezing out of thermally activated relaxation processes in the solid helium. The absence of rapid changes below 200 mK is expected since mobile dislocations could not exist in pores as small as those of Vycor. Our results support the interpretation of a recent TO experiment that showed no anomaly when elastic effects in bulk helium were eliminated by ensuring that there were no gaps around the Vycor sample.     

车内低频噪声与悬架特性参数的定量关系

基于车身乘坐室声振耦合的动态子结构修改方法，将汽车悬架系统视为附加于车身上的子结构（子系统），并结合悬架系统对路面不平度位移激励的振动传递效应，揭示出车内低频噪声的声压值与悬架系统刚度、阻尼、非悬挂质量以及轮胎径向刚度、径向阻尼问的直接定量关系。然后，通过算例及相应的实验验证了其正确性.     

舰船低频声传播的海底损失

以密度和声速连续变化的液态沉积物层和具有切变波效应的固态基底组成的水平分层海底为海底模型，分析并进行了舰船低频声场传播到海底时的反射系数仿真计算，较为准确的预报了舰船低频声场海底损失低频特性，并探讨了以此为基础的舰船海底交界处的地震波源模型。     

降低双层加肋圆柱壳低频噪声的声学设计技术

通过增大双层加肋圆柱壳的刚度降低低频噪声，使用数值仿真技术，评价结构的声学性能，发现增大双层加肋圆柱壳结构刚度，可在低频段有限频率范围降低结构的振动与声辐射。采用增大局部结构刚度的方法，对于降低水下结构的局部振动与低频噪声辐射效果显著。     

晶体振荡器测量值的不确定度评定

本文根据JJG180-2002《电子测量仪器内石英晶体振荡器》及JJF1059-1999《测量不确定度评定与表示》,介绍了用铷原子频率标准配套频标比对器及通用计数器来检测晶体振荡器频率准确度时,测量不确定度的分析。     

晶体振荡器的准确度不确定度分析

本文主要介绍了晶体振荡器的准确度测量不确定度的评定和分析。     

Identification of Power-Law Type Oscillator Phase Noise Spectra from Measurements

In this paper we demonstrate how structure functions can be used to identify power-law type spectral density components 1/fv associated with oscillator phase noise measurements when polynomial type systematic drifts are present. The technique discussed is new and novel in that it avoids the usual errors that are introduced in the measurement due to removing systematic trends in the observed data by the usual estimation detrending techniques. Several applications of the theory are given and a convenient and expedient look-up table is provided for those who perform measurements. The paper begins by summarizing accepted frequency stability measures and places these into perspective with structure functions of oscillator instability. The paper ends by showing how the rms fractional frequency deviation differs from the Allan variance; numerical examples are given.