一种新的晶体振荡器的补偿技术

晶体振荡器广泛应用于现代通信、导航、测量等领域的设备中。但是,许多设备工作在温度范围变化较大的环境中,由于石英晶体谐振器自身特殊的物理特性,温度的变化和自身的老化会导致晶体振荡器的频率发生偏移。在这种情况下,晶体振荡器就不能为设备提供稳定的时钟频率,导致设备工作异常。本文主要针对环境温度和老化对晶体振荡器输出频率的影响这个问题,通过对晶体振荡器的频率一温度与频率一老化特性的研究,利用微机输出补偿电压拉动压控电压改变晶体振荡器的频率特性,论证了一种新的晶体振荡器的补偿技术,并介绍了系统框图及原理,给出了补偿结果。     

铯束频标中压控晶体振荡器的技术要求

压控晶体振荡器是原子频标的重要组成部分。要使晶体振荡器的输出信号保持原子标准所固有的频率准确度和稳定度,所用压控晶体振荡器必须具有优良的性能。本文从分析压控晶体振荡器的技术指标对铯束频标的影响出发,提出对它的技术要求。     

石英晶体振荡器的仿真分析

通过对石英晶体振荡器的仿真分析,观察振荡器的起振和稳幅波形,测试石英晶体振荡器的振荡频率,证实理论的正确性。     

石英晶体振荡器性能参数自动测试系统研究

石英晶体振荡器具有很高的频率稳定特性和良好的温度特性,因此,被广泛应用于通信、广播、导航、电子对抗及精密测量仪器中,素有无线电通信设备的心脏之称。所以,对石英晶体振荡器性能参数的测试显得特别重要。文章提出了一种石英晶体振荡器智能测量方法。该方法利用计算机控制技术,实现自动测试石英晶体振荡器的性能参数,并打印测试结果,减少了强度,提高了检测效率。     

振动因素对航天永磁材料的影响研究

采用三因数三水平正交试验模拟了AlNiCo永磁合金在航空航天振动环境,并结合方差分析法,分析了各因素对材料磁性能的影响.结果表明,经过振动后材料未发生明显缺陷,磁性能仍在要求的范围内;各参数对磁性能的影响不显著,时间、频率、加速度对矫顽力都有一定影响,影响大小顺序为时间、加速度、频率,对其它磁性能影响很小.     

4.608MHz同步广播晶振的校准方法

4.608MHz晶体振荡器是用于同步广播的专用晶体振荡器。通常,同步广播网中各台站的晶体振荡器都要被中心台站的晶体振荡器发出的信号锁定。这就要求中心台站的晶体振荡器和各台站的晶体振荡器频率准确度在3×10~(-9)以上,即两晶振频率不能相差0.015Hz,否则就会发生失锁现象,而达不到同步广播的目的。本文就我们检定4.608MHz晶振几种方法作一介绍,所有测量方法的误差均小于1×10~(-9)。     

真空晶体镀膜的前景及应用

真空晶体镀膜的前景及应用所谓真空晶体镀膜即在真空条件下对石英晶体蒸镀上一层导电膜。通常为铬、银。使其电极形成，被做成各种频率的石英晶体振荡器。多年来，晶体振荡器被广泛应用于通讯、工业仪表及民用电器中。如低频率的石英晶体振荡器可做成各种钟表、手表及儿童...     

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。     

剩余强度模型对瓦楞纸板疲劳振动的分析研究

对瓦楞纸板进行疲劳振动试验,测定分析振动次数、加速度对瓦楞纸板塑性变形、承载能力的影响,并与未经振动材料进行比较.基于疲劳累积损伤理论中的剩余强度模型,提出瓦楞纸板疲劳振动后剩余承载能力衰减模型.疲劳加载后瓦楞纸板的剩余承载能力,不仅与载荷的循环数有关,还与疲劳加载的加速度峰值和频率有关.拟合了振动频率20Hz、加速度2.0g振动试验后,瓦楞纸板的剩余承载能力与振动次数之间的关系曲线.结果表明,随着振动次数和振动加速度的增加,瓦楞纸板剩余屈服应力减小,经过80000次振动后,其承载能力下降了38.88%.为了确保实现预期包装效果,在进行包装设计时,应考虑到瓦楞纸板的疲劳性能.     

小型温度补偿晶体振荡器问世

小型温度补偿晶体振荡器问世潇木中国计量科学研究院时间频率处研制的小型化高稳定度温度补偿晶体振荡器，近日通过技术鉴定。该产品的技术指标处于国内领先地位，并达到了国际９０年代同类产品的先进水平。随着现代通讯技术的飞速发展，对重要的通讯基础件——温度补偿晶...     

Voltage-controlled narrowband and wide, variable-range four-segment quartz crystal oscillator

In this work, our goal is to develop a voltage-controlled variable-frequency quartz crystal oscillator with narrowband response, wide, variable frequency range and the capacity to oscillate across the series resonance frequency using a four-segment configuration of a quartz crystal oscillator. In conventional quartz oscillators, the quartz resonator is inserted in the feedback loop between the input and the output of the active circuit, providing sufficient gain and the phase relation. In the oscillator developed here, the quartz crystal resonator is inserted between the loop circuit and the ground potential. The performance of the voltage-controlled variable-frequency oscillator is demonstrated across the series resonance frequency.     

HF and VHF Source Stabilization Technique Incorporating Q-Multiplied Quartz Crystal Resonator

A new approach is described for the desiga of HF/VHF crystal-controlled frequency sources exhibiting theoretical short-term stability unattainable through the use of conventional quartz oscillator design. The signal generator design uses the concept of AFC stabilization of a conventional quartz oscillator (VCXO) by means of a crystal-controlled highly selective active frequency reference. The AFC reference is a phase-shift type frequency discriminator that employs a product detector and an active Q-multiplied quartz crystal resonator. The extremely selective transmission response, large group delay, and power gain exhibited by the resonator, together with resonator phase noise levels comparable to that exhibited by the oscillator-maintaining circuit, provide the principal means for prediction of superior output signal spectral purity. Models of the resonators have been designed and constructed at 30 and 80 MHz, exhibiting 3-dB bandwidths of 30 and 160 Hz, respectively. Based on actual measurement of VHF Q-multiplied crystal resonator performance characteristics, approximately 16 dB improvement in VHF crystal-controlled frequency source spectral purity at low and moderate modulation rates is possible, compared to that attainable using the best available VHF quartz oscillator circuit designs.     

Is an oscillator-based measurement adequate in a liquid environment?

Oscillator-based measurements with quartz crystal resonators are analyzed. The investigations have shown that classical thickness monitors as well as many chemical vapor sensors based on a quartz crystal microbalance (QCM) work properly, even with simple oscillators. It was demonstrated that, for applications in a liquid environment, more sophisticated electronics are necessary. Also a comparison between the experimental results in liquids and the theoretical predictions is hardly possible without the knowledge of the oscillator behavior. As our solution, we present an automatic gain-controlled oscillator with two output signals, the oscillator frequency, and a signal that represents the damping of the quartz resonator. A calibration method is introduced, which allows one to calculate the series resonance frequency f/sub s/ and the series resistance R/sub s/ from these oscillator signals.     

Low Frequency Noise Quartz Crystal Oscillator

For years, engineers and scientists have been plagued by an extremely undesirable property of the quartz crystal unit-its significant frequency shift as a function of drive level for drive levels in excess of 10 to 100 ?W. This fact was reported by Hammond [1]. As a result, all precision and moderate precision quartz oscillators have been operated at low drive in an effort to avoid the phenomena. The author has discovered, however, that this unique property of the quartz resonator can be effectively utilized in the design of the quartz oscillator with the result of substantial improvement in oscillator short-term frequency stability. Futhermore, since the crystal frequency-drive characteristic is repeatable, maintenance of moderately high crystal drive in the oscillator circuit will not result in long-term frequency instability in excess of that required for the majority of radar and communication systems [2].     

Environmental sensitivities of quartz oscillators

The frequency, amplitude, and noise of the output signal of a quartz oscillator are affected by a large number of environmental effects. The physical basis for the sensitivity of precision oscillators to temperature, humidity, pressure, acceleration and vibration, magnetic field, electric field, load, and radiation is examined. The sensitivity of quartz oscillators to radiation is a very complex topic and poorly understood. Therefore, only a few general results are mentioned. The sensitivity to most external influences often varies significantly both from one oscillator type to another and from one unit of a given type to another. For a given unit, the sensitivity to one parameter often depends on the value of other parameters and on history. Representative sensitivity to the above parameters is given.     

Modeling of a short-term stability measuring system of quartz crystal resonators

A new numerical model of a short-term stability measuring system of quartz crystal resonators is presented. It is based on the phase bridge method using a pair of resonators driven by a low-noise source. The output signal, obtained with a phase detector, is proportional to the phase difference introduced by the resonators. The numerical transfer function of each bridge path is given by the model. The output spectral density of the phase fluctuations is computed from these transfer functions and the numerical approximation of the low-noise source. The model was applied to third overtone, SC-cut, 10 MHz BVA quartz crystal resonators. It enables the rejection of the source noise versus the resonant frequency of quartz crystal resonators to be quantified.     

Theory of Hydrogen-Maser Auto-Tuning Systems Based on the Frequency or the Phase Method

A theoretical analysis of auto-tuning systems for actively operated hydrogen (H) masers is presented. Tuning procedures based on changes in the frequency or the phase of oscillation are considered and compared. The analysis takes into account the basic results of sampling theory. The condition which should be satisfied when the reference frequency source is perturbed by white or flicker phase noise is specified. It is shown that the phase method should give better results than the frequency method when the reference source is a good quartz crystal oscillator.     

Reduction of quartz crystal oscillator flicker-of-frequency and white phase noise (floor) levels and acceleration sensitivity via use of multiple resonators

Through the use of N series-connected quartz crystal resonators in an oscillator circuit, a 10 log N reduction in both flicker-of-frequency noise and white phase-noise (floor) levels has been demonstrated. The reduction in flicker noise occurs as a result of the uncorrelated short-term frequency instability in each of the resonators, and the reduction in noise floor level is a simple result of the increase in net, allowable crystal drive level. This technique has been used in 40-, 80-, and 100-MHz AT-, BT-, and SC-cut crystal oscillators using low flicker-of-phase noise modular amplifier sustaining stages, and four series connected crystals. Total (four crystal) power dissipations of up to 30 mW have been utilized. State-of-the-art, flicker-of-frequency noise levels have been obtained with noise-floor levels (80 MHz) as low as -180 dBc/Hz. Four- to five-fold reduction in acceleration sensitivities has been determined     

Thickness measurements of single and composite thin metal films using the X-ray fluorescence technique

A high frequency quartz crystal microbalance was used to calibrate an X-ray fluorescence (XRF) system employing a ²⁴¹Am exciter source of 40 mCi an. Si(Li) detector with a resolution of 230eV at 5.9 keV. The quartz crystal monitor was previously calibrated down to about 200 Å using an interferometer. The XRF system was then used to extend the measurements down to about 15 Å employing quartz crystal oscillator measurements for comparison. Single and composite thin film layers of copper and silver were prepared on thin mica substrates using the vacuum evaporation method. The data indicate the advantage of this technique for the accurate measurement of ultrathin film thicknesses with the possibility of detecting changes in material densities.