【作者】 刘宇；

【导师】 宣宗强； 魏西峰；

【作者基本信息】 西安电子科技大学 ， 仪器仪表工程， 2014， 硕士

【摘要】 从人们认识到时间以来,能够准确的获取测量时间的频率源一直是人们所追求的目标,石英晶体振荡器由于具有很高的空载品质因数和极小的接入系数,因此具有良好的频率稳定性而作为重要的时钟信号基准来使用。同时,便携式电子产品的飞速发展,就手机来说2013年一年全球的出货量达到18亿部,一部手机至少会有一个石英晶振,需求量巨大,在晶体振荡器高性能、小型化、低功耗、高频率稳定度等多重要求下,晶体本身所固有的温度特性,成为影响其性能并且制约其应用的一种重要因素,因此出现了专门针对晶体温度特性而进行补偿的芯片,现在已有数字温补晶振、微机补偿晶振、模拟温补晶振等几种不同方式补偿的晶体振荡器,模拟温补晶振以其在芯片面积、成本、补偿精度等方面很好的平衡,得到了广泛的应用,获得高频率稳定度的简单易集成的模拟温补晶振也是本文的研究重点。本文设计了一种超高频率稳定度的模拟温度补偿晶体(ATCXO)振荡器电路,该芯片利用先进的模拟集成电路制造工艺,将模拟补偿电路及压控晶体振荡器集成于一颗芯片中,使晶体在使用时只需和一颗芯片搭配使用(可封装于同一个管壳内),即可在较宽温度范围内提供高精度的频率源。论文首先研究了石英晶体的特性和等效电路,讨论了ATCXO的种类和架构,提出了晶体振荡器频率随温度漂移的解决办法。利用电路实现了温度检测、五次方函数发生器、压控振荡器(VCXO)等电路,并通过芯片内嵌的EEPROM及ROM对补偿电路进行修调,可进一步提高其补偿精度。其中带隙基准电路采用Cascode结构,电源抑制比高,VCXO选用皮尔斯电容三端式振荡器,并针对其缺点进行改进,补偿电容采用反型MOS可变电容,实现起来成本低,接着利用HSPICE傅里叶分析研究了CMOS在大信号下的电容特性,五次方函数发生器采用CMOS工艺,成本低,功耗小,修调电路通过对五次方函数电压的温度拐点、五次项系数、四次项系数、三次项系数、一次项系数、晶振起振频率等参数进行事先调整,通过参数的调整可对不同规格的晶体振荡器进行频率补偿,实现稳定的频率输出。本文中的ATCXO采用的五次方函数补偿比三次函数补偿更加精准,补偿过得温度频率稳定度更加高。最后,在完成电路原理分析及子电路设计的基础上,采用先进的0.35μm模拟芯片生产工艺,绘制版图且完成流片,设计出满足移动通讯、数字网络和各种便携式电子产品等需求的芯片,供电电压2.7~5.5V,频率为10MHz~52MHz,其在-40~85℃(-20~70℃)范围内,随温度频率偏移小于±1ppm(±0.5ppm),用于弥补国内这种芯片被国外企业垄断的现状。整个设计流程在linux系统下基于HSPICE仿真工具、Cadence集成电路设计环境完成的。更多还原

【Abstract】 From the time since it was recognized, it is possible to obtain an accurate measurement of time frequency source has been one of the objectives pursued. Quartz crystal oscillator has a high no-load quality factor(Q) and minimal access coefficient, so it has good frequency stability and precision of the clock signal as an important benchmark to use. Meanwhile, the rapid development of portable electronic products.The year 2013 global Mobile phone shipments reached 1.8 billion, a cell phone,at least there will be a quartz crystal, The huge demand in the crystal oscillator performance, small size, low under the multiple requirements power, high frequency degree, temperature characteristics inherent in the crystal. It becomes a factor restricting the application temperature range, and the application, resulting in a specific characteristic of the crystal temperature compensation chip. Now there are digital temperature compensated crystal oscillator, the Microcomputer Compensated crystal oscillator, ATCXO compensation in several different ways of crystal oscillator. TCXO in the simulation of chip area, cost, compensation, precision, have good balance, obtained the widespread application. The research focus to obtain high frequency stability is easy to simulate temperature integration to the compensated crystal oscillator.This paper presents an ultra-high frequency stability of analog temperature compensated crystal(ATCXO) oscillator circuit. The chip using advanced integrated circuit manufacturing technology. The analog compensation circuit and voltage-controlled crystal oscillator integrated in a single chip, making crystals and when using only a single chip with the use(which can be packaged in the same envelope), to provide high-precision frequency source over a wide temperature range. Firstly, studied the characteristics and equivalent circuits for quartz crystal, discusses ATCXO types and architecture, made crystal oscillator frequency elegant solution with temperature. Use the circuit to achieve a temperature probe, a five-th order function generator, a voltage controlled oscillator(VCXO) and other circuits, and through chip embedded EEPROM and ROM trimming the compensation characteristic can further improve the accuracy of their compensation. Where the bandgap reference circuit using cascode structure, it has high power supply rejection ratio. VCXO selects the Pearce capacitor of three terminal oscillator, and for its shortcomings were improved, the compensation capacitor using MOS capacitor to implement a low cost, then use HSPICE Fourier analysis of the CMOS capacitance characteristics under large signal, The five-th order function generator using CMOS technology, low cost, low power consumption, trimming circuit voltage by five square function of the temperature of the inflection point, five coefficients, four coefficients, three coefficient, a key factor, since the crystal oscillator frequency parameters such as memory adjustment. By adjusting the parameters, can be of different sizes crystal oscillator frequency compensation, to achieve a stable frequency output function quadrillion compensation herein. The Five-th order function compensation in this paper by using the ATCXO more accurate than using a cubic function, compensation had more high temperature frequency stability.Finally, based on the completion of circuit theory analysis and design of the sub-circuits,using the advanced 0.35 um analog chip production process, draw the layout and complete the flow sheet. Designed to meet the mobile communications, digital networks and a variety of portable electronic products and other needs. the chip supply voltage2.7~5.5V, frequency of 13 MHz, it is within-40 ~ 85 ℃(-20 ~ 70 ℃) range,with temperature frequency deviation of less than ± 1ppm(± 0.5ppm), used to make domestic chip monopoly status of foreign enterprises. The whole design process in the Linux system HSPICE simulation tool, Cadence integrated circuit design environment based on.更多还原