Wide-Band Varactor-tuned Coaxial Oscillators

An experimental investigation into the effects of package and circuit reactances on wide-band varactor-tuned oscillators is described. The results are used to design an X-band Gunn coaxial oscillator with a tuning range in excess of 3 GHz. It is shown that the stray reactance, junction capacitance, and bond-wire inductance affect the varactor tuning characteristics. The characteristics are conveniently displayed by the reflection phase variation with tuning voltage and frequency. A general theory for wide-band varactor-tuned oscillators is presented which is related to the impedance characteristics. These results are used to design three coaxial varactor-tuned oscillators. The first two oscillators are series arrangements while the third oscillator is a parallel arrangement. A simple circuit technique is used to improve the tuning range of each arrangement. This technique is shown to increase the coupling to the varactor diode and decrease the oscillator Q by reactance compensation.     

神经网络曲线拟合在温补晶振上的应用

石英晶振作为重要的频率源器件,其频率稳定度至关重要。但温度对石英晶振的影响很大。传统的微处理器温度补偿晶振中在拟合曲线时算法简单,导致软件引起的误差较大。利用了神经网络算法在曲线拟合上的应用,拟合出补偿电压与温度之间的函数关系,微处理器根据温度传感器采集的温度控制AD芯片产生补偿电压,从而使压控振荡电路输出稳定的频率的目的。实验结果表明:温度在-10⁸0℃时,频率稳定度达到±0.35 ppm,比未补偿时提高了近20倍,比其他曲线拟合方法得出的效果要好。     

硅振荡器的抗高过载实验设计与分析

硅振荡器是一种在高过载条件下有可能代替石英晶体振荡器为应用系统提供稳定时钟的振荡器。对硅振荡器开展高过载实验研究,具有重要的应用价值。论文以LTC6909I型硅振荡器为实验对象,对高过载环境下可能产生的频率漂移及是否损坏这两个主要方面进行了实验研究。实验证明了硅振荡器能经受高过载环境的考验,可以代替石英晶体振荡器为应用系统提供稳定时钟。     

Some aspects of the theory and measurement of frequency fluctuations in frequency standards

Precision quartz oscillators have three main sources of noise contributing to frequency fluctuations: thermal noise in the oscillator, additive noise contributed by auxiliary circuitry such as AGC, etc., and fluctuations in the quartz frequency itself as well as in the reactive elements associated with the crystal, leading to an f^-1type of power spectral density in frequency fluctuations. Masers are influenced by the first two types of noise, and probably also by the third. The influence of these sources of noise on frequency fluctuation vs. averaging time measurements is discussed. The f^-1-spectral density leads to results that depend on the length of time over which the measurements are made. An analysis of the effects of finite observation time is given. The characteristics of both passive and active atomic standards using a servo-controlled oscillator are discussed. The choice of servo time constant influences the frequency fluctuations observed as a function of averaging time and should be chosen for best performance with a given quartz oscillator and atomic reference. The conventional methods of handling random signals, i.e., variances, autocorrelation, and spectral densities, are applied to the special case of frequency and phase fluctuations in oscillators, in order to obtain meaningful criteria for specifying oscillator frequency stability. The interrelations between these specifications are developed in the course of the paper.     

基于CMOS反相器石英晶体振荡电路的PSPICE仿真

石英晶体振荡器是很常用的电子器件,在电路设计和教学工作中经常需要对石英晶体振荡电路进行仿真分析。通过实例介绍使用PSpice仿真软件对石英晶体振荡电路进行模拟仿真的方法。针对石英晶体振荡器的等效电路,分析了石英晶体的串联和并联谐振频率。讨论了石英晶振的仿真模型,并在仿真器中观察其起振波形和稳幅波形,测试其振荡频率。通过对元件的参数扫描,分析不同参数对振荡器的影响。     

基于皮尔斯振荡器的8MHz晶振电路设计

分析了石英晶体的等效模型和性能参数,设计了一款基于皮尔斯振荡器的8 MHz晶振电路,主要包括皮尔斯电路、使能控制及隔离电路、偏置电路和整形及电平移位电路.针对数字电路时钟为方波且数字电压域与模拟电压域不同的问题,设计了一个整形及电平移位电路,将晶体振荡器输出的正弦波整形成方波,且电路实现了双电压域工作.基于华宏0.11...     

基于EWB的可编程调频微型电动机三相方波变流电源设计

随着现代电力电子装置,电气设备的快速发展,使得驱动电源得到进一步的发展,本文设计了一种转换效率、对称性以及稳定度等特性都比较好的数字式三相方波变流电源。所设计电源将石英晶体谐振器作为产生高频的方波信号的高频振荡器,然后用可编程的思想进行分频,再环形分配,处理成所需要的频率数值,最后通过运算放大器以满足输出电压,输出功率的要求,并且同模拟振荡式相比,它的频率稳定度要高很多。根据设计的三相方波变流电源的模型在电子工作平台EWB中进行搭建,对数字式三相方波变流电源的波形、输出电压、输出电流等进行仿真研究,通过对仿真结果分析可以验证其设计方案的准确性和可行性,这为以后搭建三相方波变流电源的硬件电路提供了一定的理论依据。     

LSA relaxation oscillations in a waveguide iris circuit

Large-signal computer simulations of GaAs LSA relaxation oscillations in an X-band waveguide iris circuit are presented. The study is focused on a particular oscillator and a realistic model of an experimental circuit is used. However, the results are typical for other LSA relaxation oscillators. Basic features of the microwave circuit, characteristic voltage and current waveshapes, frequency tuning with bias voltage, and oscillator starting transients are discussed. The RF output power is shown to build up in less than ten cycles. Circuit optimization for high dc to RF conversion efficiency is discussed and circuit data for nearly 30 percent efficiency are given. Finally, efficiency degradation is discussed when doping gradients are present, and effciencies of 15 and 10 percent appear possible for doping gradients as high as 20 and 60 percent, respectively. Hence, the LSA relaxation mode is shown to be less sensitive to doping gradients than the sinusoidal LSA mode.     

A digitally temperature-compensated crystal oscillator

The base frequency of oscillators used in the Global System for Mobile Communication (GSM) network or Global Positioning System (GPS) receiver applications needs to be very stable with respect to temperature and supply-voltage variations. One approach to obtain extremely good frequency stability is the use of oven-stabilized crystal oscillators. With this kind of oscillator, a frequency stability versus temperature of a few ppb versus the standard temperature range can be achieved. In this paper, a digitally compensated crystal oscillator is described. The system provides a frequency stability of (Δf)/f<1.5 ppm for a temperature range of -40°C to 90°C compared to about ±20 ppm for a noncompensated crystal. The core of the system is an application-specified integrated circuit (ASIC) fabricated in a standard 0.8-μm CMOS process. The power consumption for the oscillator running at 13 MHz is 100 mW. The final device equipped with the ASIC, crystal blank, and a few external components fits into a 14×9×3 mm³ package     

The use of saw oscillators to suppress fm noise in local oscillators for on-board satellite applications

SAW oscillators can provide fundamental frequency operation to above 1·5 GHz, with stability and FM noise performance approaching that offered by bulk crystal oscillator technology. Their high fundamental frequency, small size and rugged construction gives SAW technology a unique capability at UHF and microwave frequencies. The low FM thermal noise floor associated with fundamental frequency operation can be combined with the stability and low close-to-carrier noise of multiplied bulk crystal oscillators by locking a high frequency SAW oscillator to a bulk crystal reference. SAW oscillator stability is compatible with conventional phase-locked-loop techniques and also with injection lock stabilization, and their own low close-to-carrier FM noise ensures that such locked sources exhibit minimum phase noise. Furthermore, locked oscillator phase noise is not significantly degraded when extreme operating conditions, such as those experienced in space applications, demand a reduced SAW device Q for reliable locking using either technique. Use of a PLL avoids any need for reference frequency multiplication, and provides additional design flexibility with respect to reference frequency selection and phase noise optimization. Injection locking offers design simplicity and uses fewer frequency control components, which can contribute additional noise in PLL sources.     

Design and Performance of X-Band Oscillators with GaAs Schottky-Gate Field-Effect Transistors

The circuit construction and design of an X-band oscillator with a GaAs Schottky-gate FET have been studied. The oscillation characteristics including stability and noise performance have been examined in order to clarify the position of a GaAs FET as a microwave solid-state oscillator device. The experiments have revealed that 1) the GaAs FET simultaneously possesses the most desirable features of both Gunn and IMPATT oscillators, i.e., low bias voltage operation and fairly high efficiency, and 2) it is situated between Gunn and GaAs IMPATT oscillators with respect to noise properties. The results indicate that the GaAs FET oscillator will soon be joining the family of microwave solid-state oscillators as a promising new member.     

空间用晶体振荡器热真空性能研究

空间用晶体振荡器是航天器的重要元器件,为航天器提供计时和产生标准频率.晶体振荡器的使用性能高度依赖于应用和任务环境,热应力、机械应力、辐射应力等都对石英晶体振荡器的使用性能造成影响.在空间真空热环境下,晶体振荡器使用性能与地面常压环境下有很大的不同,为了检验空间用石英晶体振荡器的热真空环境适应性,文章针对空间用石英晶体...     

Simulation Investigation of Millimeter Wave Varactor-tuned Transmission Cavity-stabilized Oscillator

A new circuit configuration for millimeter wave varactor-tuned transmission cavity-stabilized oscillator has been proposed in this paper. Compared to conventional varactor-tuned reflection cavity-stabilized oscillator, in this configuration, a high quality factor transmission cavity directly coupled to varactor diode is employed to improve the performances of the oscillator. The operation frequency of this oscillator can be tuned by varying the resonant frequency of the transmission cavity through changing bias voltage of the varactor diode. An equivalent circuit model for the oscillator has been presented in order to theoretically investigate the performance characteristics of the oscillator. On the basis of this model, electrical tuning characteristics have been studied. Mode jumping phenomena during electrical tuning process have been analyzed for obtaining stable operations of the oscillator. The analytical formulae of quality factor and efficiency have been derived in terms of relevant circuit parameters. Particular emphasis has been paid on several circuit parameters which have a substantial impact on circuit performance. Some design considerations have been pointed out according to the simulation results, which are useful to the design and fabrication of this type of oscillators.     

基于orCAD／PSpice的晶体振荡电路设计仿真

通过对电容三点式振荡电路和石英晶体振荡器等效电路的计算分析,设计并改进了石英晶体振荡器电路。在OrCAD／PSpice环境中完成了电路的时域和频域仿真分析,对影响振荡电路起振特性的因素进行了探讨,进一步验证了PSpice电路仿真设计的合理性和可靠性。给出了发生电路的振荡、稳幅波形,测量了振荡周期和振荡频率,并与理论值做出比较。结果表明,设计的振荡电路波形好,振荡频率稳定,易于实现,可广泛应用于工程设计领域。     

A high-frequency electronically tunable quadrature oscillator

An architecture composed of mutually regenerative oscillators is introduced. It has been used to design a low-noise high-frequency voltage-controlled oscillator (VCO) capable of producing two output signals in quadrature with essentially identical properties. The phase relation between the quadrature outputs is frequency dependent and extremely stable. A novel way of coupling the regenerative oscillators is suggested in order to improve the frequency stability of the coupled oscillator system. Results obtained from a test chip have verified the viability of the oscillator concept. The oscillator circuit has been realized in a medium-frequency bipolar process. The tuning range extends to 500 MHz. At an oscillation frequency of 200 MHz, measured phase noise was -121 dBc/Hz at 1-MHz distance from the carrier.<>     

Application of RPN analysis to parameter optimization of passive components

In the trend toward the development of electronic products that are compact and lightweight, as portable consumer electronic products, such as the cell phone, Bluetooth, GPS, W-LAN, digital camera, wireless phone, and notebook computer, increase in demand, the frequency control components needed for communications related industries receive increased attention. The crystal oscillator is widely used as a frequency selective passive component in communications related industries because of excellent characteristics, such as temperature stability and a low loss. A crystal oscillator consists mainly of a quartz crystal and an IC that controls the oscillation circuits, and is applied to high precision communications products, requiring high frequency accuracy. A crystal oscillator with an output frequency that deviates or is unstable will seriously degrade the quality and functionality of an expensive communications product.This present research investigates the crystal oscillator manufacturing processes, developing risk priority number analysis specifically for critical-to-quality processes and identifying the optimum priority for improvements in the process quality. Using Taguchi experimental design techniques the optimal parameter design is determined for quality characteristics and a mathematic programming method establishes an objective mode for monitoring quality. Lastly, the present research uses a real case to verify the modes proposed in this project, to enhance customer satisfaction, and produce crystal oscillators with a competitive advantage.     

Injection Locking of Klystron Oscillators

If certain criteria are met, a microwave oscillator may be synchronized by the injection of a controlling signal into the oscillator cavity. Synchronization is dependent upon oscillator circuit parameters, the ratio of injected power to oscillator power, and frequency difference between the free-running oscillator and the injection signal. Locking has been observed with injection signals 70 db below the oscillator output and 30-db ratios have been demonstrated to be easily realizable. Injection locking may be considered a form of amplification that permits taking advantage of the fact that microwave oscillators are smafler, lighter, less expensive and more efficient than amplifier devices. The low-frequency theory of Adler is shown to describe accurately the locking phenomena in reflex klystron oscillators and the transient response is extended to determine limitations on the amplification of modulated signals. Experimental verification of the theory is shown for 180/spl deg/ phase modulation of the locking signal at rates up to 100 kc for a VA-201 klystron. Design relations and curves are presented and applications and improvements are discussed.     

Frequency Demodulator Using an Injection-Locked Oscillator: Analysis and Design

This letter introduces a systematic procedure for the design of direct frequency demodulators based on injection locking. An oscillator is synchronized to the modulated carrier and the modulation signal is extracted from the time-variation of the current or voltage of the bias-network. The synchronized oscillator is optimized with harmonic-balance techniques specifically developed for this demodulation function. The circuit performance under modulated conditions is evaluated with envelope transient and using a modified Poincare map. The new techniques are illustrated by means of their application to a direct frequency demodulator at 1.2 GHz. The letter shows that provided accurate nonlinear analysis and design techniques are used, injection-locked oscillators constitute a good option for the implementation of direct frequency demodulators.     

CMOS realization of single-resistance-controlled and variable frequency dual-mode sinusoidal oscillators employing a single DVCCTA with all-grounded passive components

In this paper, two new designs are proposed for sinusoidal oscillators based on a single differential voltage current conveyor transconductance amplifier (DVCCTA). Each of the proposed circuits comprises a DVCCTA combined with passive components that simultaneously provides both voltage and current outputs. The first circuit is a DVCCTA-based single-resistance-controlled oscillator (SRCO) that provides independent control of the oscillation condition and oscillation frequency by using distinct circuit parameters. The second circuit is a DVCCTA-based variable frequency oscillator (VFO) that can provide independent control of the oscillation frequency by adjusting the bias current of the DVCCTA. In this paper, the DVCCTA and relevant formulations of the proposed oscillator circuits are first introduced, followed by the non-ideal effects, sensitivity analyses, frequency stability discussions, and design considerations. After using the 0.35-μm CMOS technology of the Taiwan Semiconductor Manufacturing Company (TSMC), the HSPICE simulation results confirmed the feasibility of the proposed oscillator circuits.     

用于晶体振荡器温度补偿的次方电压产生方法

为了获得更高精度的时钟源,需要对晶体振荡器进行温度补偿以便减小频率随温度的变化。对比晶体振荡器不同的温度补偿方式,模拟温度补偿具有较高的性能,而模拟温度补偿电路的主要模块就是获取与温度成次方关系的补偿电压。文中采用了一种模拟乘法器的方法来获得与温度成不同指数关系的电压,在全差分放大器的输入端接入4个MOS管,利用其工作于线性区时的电流电压关系并结合全差分放大器来实现两个模拟量之间的相乘,进而获得与温度成1次方、2次方、3次方、4次方和5次方关系的补偿电压。获得的这些电压通过加和电路叠加后即可用于晶体振荡器的高阶温度补偿。通过仿真,得到全差分放大器的差模增益为78.6 dB,乘法器可以实现两个信号的相乘,且应用该方法进行补偿的晶体振荡器的频率偏移为±2 ppm。