标题: 高效能CMOS展频讯号产生器之设计与分析
Design and Analysis of High Performance CMOS Spread-Spectrum Clock Generators
作者: 谢义滨
Yi-Bin Hsieh
高曜煌
Yao-Huang Kao
电信工程研究所
关键字: 差异积分调变器;频率调变;展频讯号产生器;分数讯号合成器;双点调变;电压控制振荡器调变;delta-sigma modulator;frequency modulation;spread spectrum clock generator;fractional-N synthesizer;two-point modulation;VCO modulation
公开日期: 2007
摘要: 在消费电子中随着高速传输需求的日益增加,工作频率已达到数仟兆赫。因为工作频率增加时,这些装置所产生及辐射的电磁干扰也快速递增。所以一个低成本且有效降低电磁干扰的方法是目前所需要的。目前有很多方法可以来减少电磁干扰,在这些方法中,展频讯号时脉正受到许多瞩目因为其系统成本是最低的,其原理为在一定的速度及方法下调变时脉使其有效抑制电磁干扰。
本论文介绍四个不同展频讯号产生器将,其中用了三种不同的调变方法。首先研究一个传统的分数差异积分调变展频讯号产生器,其原理为使用差异积分调变器来调变除法器。传统的差异积分调变器的输入范围有限制,当展频大小超过其输入范范围时,展频讯号产生器会无法正常工作导致大幅降低电磁干扰抑制能力及时间抖动成效。因此本论文的第一个主题为克服这个限制并发展出一个新型分数差异积分调变展频讯号产生器且具有广输入范围的差异积分调变器。
接着研究一个使用电压控制振荡器调变的展频讯号产生器。传统的电压控制振荡器调变的展频讯号产生器的其中一个问题为在产生三角波时有太多的限制,三角波为普遍使用的调变型式。另外一个困难为所需要的电容面积太大(大于数十个十亿分之一法拉)使其很难整合在晶片中,其原因为其所需要的回路频宽太小了。本论文中所提出的电压控制振荡器调变的展频讯号产生器使用了一个双回路滤波器并同时使用了一个特定的充电泵来克服这两个问题。
最后,本论文发展出两个使用双点调变机制的新型的展频讯号产生器,其同时改变除法器及电压控制振荡器。其中一个针对双点调变机制中的时间抖动及电磁干扰做详细的分析。为了研究双点调变机制在高速传输的应用,进而发展出另一个适用于序列进阶技术附加装置的展频讯号产生器并证明其可符会其规格。双点调变中的全导通特性可以增加调变频宽使得调变的准确度及由差异积分器所产生的时间抖动可以一起改善。此技术导致所提出的展频讯号产生器具有面积小及功耗低的特点。
With the growing demands of high data rate transmission in consumer electronics, the operation frequency is toward several GHz. As the operation frequency increases, the electromagnetic interference (EMI) generated and radiated by those devices also increases rapidly. Therefore, an effective and low cost method to reduce EMI is becoming imperative. There are many techniques to reduce the EMI. Among these techniques, spread spectrum clocking (SSC), modulating the clock in a given rate and style such that the EMI is lower, is receiving many eyes because the cost to the system is minimal.
In this thesis, four different SSCGs with three kinds of modulation schemes are presented. First, a conventional fractional-N based SSCG, using a ΔΣ modulator to modulate the divider, is studied. The input range of the conventional ΔΣ modulator is limited. When the spread ratio is exceeded its input range, the SSCG will be breakdown, and the EMI reduction and jitter performance will be degraded very much. Thus the subject of this dissertation is to overcome the limitation and to develop a new fractional-N based SSCG with a wide input range of ΔΣ modulator.
Then, a voltage controlled oscillator (VCO) modulated SSCG is investigated. One major issue of the conventional VCO modulated SSCG is that it has much constraints on the generation of the triangular waveform, which is a popular modulation profile. Another difficulty is the required large capacitance (more than tens of nF) to make it hard totally integration because the loop bandwidth is very small. The proposed VCO modulated SSCG overwhelms these two issues by combing a dual-path loop filter with a particular charge pump.
Last of all, two new SSCGs with a two-point modulation scheme are built. Both the divider ratio and the voltage controlled oscillator are varied. One is focused on the jitter and EMI analysis of the two-point modulation scheme. In order to evaluate the high data rate application of two-point modulation, the other is developed for the application of serial advanced technology attachment (SATA) and is proven to meet the specifications of SATA. An all-pass characteristic of the two point modulation can enhance modulation bandwidth in order that the modulation profile accuracy and jitter performance caused by the ΔΣ modulator can be improved at the same time. This technique results in the proposed SSCG with small area and low power consumption.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT009313821
http://hdl.handle.net/11536/78473
显示于类别:Thesis


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