Voltage-controlled crystal oscillators

The quartz crystal oscillator is normally thought of as a stable generator of a fixed frequency. It is possible, however, to design and construct voltage tunable quartz crystal oscillators that can be electrically tuned over a frequency range on the order of ±0.3 percent of the crystal frequency. This is accomplished with a nonlinearity between frequency and voltage on the order of 0.1 percent. Moderately good long-term frequency stability and low phase noise is exhibited by the oscillators. A reactive network including varactor diodes is used to provide a voltage variable reactance which, in combination with a quartz crystal network, forms a resonator having an antiresonant frequency that is a linear function of tuning voltage. The basic reactance network is not practically realizable. However, the application of one of Norton's network transformation theorems results in a realizable network. The oscillator described is very simple in design and provides an inexpensive solution to a large number of signal processing and measurement problems.     

高振动石英晶体振荡器

新的设备特性使苛刻应用中的频率控制更稳固 我们通常认为在电子系统中,石英晶体振荡器是最易碎的元件之一.     

微小型恒温晶体振荡器

本文介绍体积为20×12×5(mm)和16×16×5.5(mm)两种结构的微小型恒温晶体振荡器的设计制造、工艺以及为微型化而对晶体谐振器进行专门的设计安装。详细介绍了对主振电路、射随级和加热及控温电路采用混合集成和表面安装技术而实现了微型化。对已提供给航空、航天电子工程使用的,频率从100kHz到80MHz范围部分产品进行的全面技术指标测试结果进行了分析。还对多信号输出晶体振荡器的工作原理作了简单介绍。     

Conditions for start-up in crystal oscillators

The influence of parasitic elements on crystal oscillator start-up is examined. Both theoretical analysis and computer simulation are used to identify circuit parameters affecting oscillator start-up and methods of ensuring reliable operation are indicated. The results are verified by experimental measurements.     

Design considerations for high-frequency crystal oscillators

The deleterious effects of crystal shunt capacitance and series resistance on the performance of series-mode oscillators are discussed. When the parasitic capacitance across the crystal significantly modifies the transconductance of the amplifying stage the circuits can become susceptible to a parasitic second mode of oscillation above the series-resonance frequency of the crystal. A simple model that can sufficiently describe such crystal oscillator circuits was developed and used to derive simple design equations that can accurately predict the behavior of these circuits. The design equations should be especially useful for a reliable design in cases when it is not practical to use an additional inductor to compensate for the parasitic shunt capacitance of the crystal. It is shown theoretically that the inclusion of this capacitance in the feedback path reduces the total effective capacitance in the tank circuit, which is tuned to the desired overtone frequency. This creates a second mode of oscillation frequency which is higher than the desired crystal resonance frequency. The ranges of loop-gain and tank resistance values that can prevent this parasitic mode of oscillations are derived. It is also shown that the useful loop gain for the desired oscillations to start is restricted to a similar region by the crystal shunt capacitance and series resistance     

Analog ALC crystal oscillators for high-temperature applications

Fundamental mode and third-harmonic mode integrated high-performance automatic level controlled (ALC) crystal oscillators for high-temperature applications (up to 250°C), are described in this paper. These oscillators were designed for a pressure measurement system in high-temperature environments, where the output signal is the difference between both generated frequencies. Frequency variations smaller than 0.0001 ppm/s for each oscillator and a frequency drift of about 2.5 ppm/year of the frequency difference are the measured performance concerning, respectively, the short-term (1 s) and long-term frequency stability of these integrated high performance crystal oscillators over the 30°C-225°C temperature range. Other important characteristics are the very stable and constant oscillation levels (~1.1 Vpp), the small second-harmonic distortion (~60 dR), and the phase noise (~95 dB at 50 kHz shift). The characteristics of these oscillators make them also suitable for many other measurement systems (time, temperature, and other physical and chemical quantities), especially if they are constrained to operate under severe temperature conditions     

Thermal sensitivity of photonic crystal fibers in opto-electronic oscillators

ith temperature and prospect of thermal stability in the OEO using passive techniques is great when a combination of HC-PCF and SMF-28 are employed as fiber delay lines.     

Comment on "Variable frequency crystal oscillators"

In a practical variable frequency crystal oscillator the difference between the operating and series resonant frequencies is always smaller than fp- fs. This limitation can be overcome by a negative capacitance realized using a NIC which does not seriously degrade overall stability.     

取代石英晶体的MEMS振荡器和全硅振荡器

“时钟和振荡器是所有电子系统的心跳”,正如Silicon Labs公司副总裁Dave Bresemann所说的,振荡器可谓电子系统正常运行的根本。     

用于遥测系统中的晶体调频振荡电路分析

本文主要分析遥测发射机中的晶体调频振荡电路,并导出晶体调频网络的参数与频率之间的关系式.最后,给出晶体调频振荡电路的实验结果和实际应用.     

Investigation of EMI-induced noise spectrum in an enhancement-type MOSFET

This paper models the time domain and frequency domain characteristics of the noise spectrum of a MOSFET device under varying EMI conditions. The theoretical results are compared with experimental measurements. Both sets of results reveal that the magnitude of the EMI-induced noise is governed by the pulse height, the output load, the parasitic capacitance, the interference frequency and the interference amplitude. Furthermore, it is shown that a higher interference amplitude or frequency increases the harmonic noise. The theoretical method presented in this paper provides a convenient means of evaluating the EMI effects and signal-to-noise ratio (SNR) of MOSFETs and similar wavelength devices.     

State of the art—Quartz crystal units and oscillators

The paper discusses progress made in the field of quartz crystal units and quartz crystal controlled oscillators over the past few years. The field is reviewed in general, but several accomplishments which are thought to be of special importance, are discussed in detail. These subjects include, among others, quartz vibrator characteristics and enclosures, modes of motion including the "trapped energy" concept and long-term drift (aging) of crystal units. The characteristics of various types of oscillators are reviewed including temperature compensated and high precision types, and the problem of short-term stability of crystal controlled oscillators is discussed. Precision oscillators are available today with a daily drift rate as low as a few parts in 10¹¹and a short time stability better than a few parts in 10¹⁰for a time period of one millisecond.     

GNSS快速驯服高稳晶振的设计与实现

基于各个领域对高精度时间频率信号的需求,实现了一种利用GNSS信号驯服高稳晶振的方法.采用3σ法则剔除测量相位差数据中的奇异值,并利用Kalman滤波对相位差数据进行滤波以抑制测量噪声.通过改变压控晶振的电压控制字对频率初始准确度为5×10-8的恒温晶振进行驯服,经过约600 s的快速驯服,使得晶振的频率准确度优于4....     

A new nonlinear model of EMI-induced distortion phenomena in feedback CMOS operational amplifiers

This paper deals with distortion phenomena induced by radio-frequency interference (RFI) in analog integrated circuits and it concentrates on the effects induced by RFI on the operation of feedback CMOS operational amplifiers (opamps). In particular, the paper describes a new nonlinear model, which makes possible the prediction of upset in the opamp output nominal signal when RFI is superimposed on the input nominal signals. Such a model can be employed when the transistors of the input differential pair are driven by RFI either in strong or weak nonlinear operation. Results of experimental tests performed on a Miller CMOS opamp connected in the voltage follower configuration are presented and compared with model predictions.     

Experimental study and theoretical prediction of aging induced frequency shift of crystal resonators and oscillators

Frequency shift, due to quartz crystal resonator aging, has been identified as one of the most important quality control problems of quartz crystal products. The problem becomes more significant due to the device miniaturization and high precision standards for telecommunication applications. Since aging induced frequency shift occurs during a long time frame, it is necessary to predict the long-term behavior of the devices based on the short-term data obtained under an accelerated environment. One the other hand, frequency shift is associated with quite large random variation, and thus, a proper probabilistic theory should be used for analyzing test data and for developing a reliable prediction model. Accelerated testing was performed for various types of crystal resonators under elevated temperatures. The frequency shifts of the devices were measured at different testing periods. Markov chain model was used to characterize the frequency shift of the devices. The obtained short-term test results were used for calibrating the probabilistic transition matrix of Markov chain model. The model can then be used for predicting the long-term frequency shift. The time–temperature superposition principle in viscoelasticity was adopted to address the shift in time under different temperatures.     

Jitter in ring oscillators

Jitter in ring oscillators is theoretically described, and predictions are experimentally verified. A design procedure is developed in the context of time domain measures of oscillator jitter in a phase-locked loop (PLL). A major contribution is the identification of a design figure of merit κ, which is independent of the number of stages in the ring. This figure of merit is used to relate fundamental circuit-level noise sources (such as thermal and shot noise) to system-level jitter performance. The procedure is applied to a ring oscillator composed of bipolar differential pair delay stages. The theoretical predictions are tested on 155 and 622 MHz clock-recovery PLL's which have been fabricated in a dielectrically isolated, complementary bipolar process. The measured closed-loop jitter is within 10% of the design procedure prediction     

Noise in Gunn oscillators

We estimate the ultimate noise of Gunn oscillators in the absence of 1/fnoise. The basic noise source considered is thermal or Johnson noise augmented by intervalley noise of carriers hopping between the high and low mobility bands. For example, for Qext= 10²and Pout=10^-1W we estimate δfrms≈ 1-2 Hz, and AM noise relative to the carrier of -156 dD, both measured in 1-kHz bandwidths.     

Grid oscillators

Loading a two-dimensional grid with active devices offers a means of combining the power of solid-state oscillators in the microwave and millimeter-wave range. The grid structure allows a large number of negative resistance devices to be combined. This approach is attractive because the active devices do not require an external locking signal, and the combining is done in free space. In addition, the loaded grid is a planar structure amenable to monolithic integration. Measurements on a 25-MESFET grid at 9.7 GHz show power-combining and frequencylocking without an external locking signal, with an ERP of 37 W. Experimental far-field patterns agree with theoretical results obtained using reciprocity.