搜索
查看: 2281|回复: 11

[讨论] 哪位兄弟能解释一下,CCDF是么子,干什么用的?

[复制链接]

该用户从未签到

发表于 2006-3-10 13:59:00 | 显示全部楼层 |阅读模式
谢谢:)

该用户从未签到

发表于 2006-3-10 15:54:00 | 显示全部楼层
<P><FONT size=2>Complementary Cumulative Distribution Function</FONT></P>
<P><FONT size=2>中文名称是互补累积分布函数</FONT></P>
<P>A CCDF curve shows how much time the signal spends at or above a given power level. The power level is expressed in dB relative to the average power. The percentage of time the signal spends at or above each line defines the
probability for that particular power level. A CCDF curve is a plot of relative power levels versus probability.</P>

<P align=right><FONT color=red>+5 RD币</FONT></P>
[此贴子已经被作者于2006-3-12 15:19:42编辑过]

该用户从未签到

发表于 2006-3-11 11:11:00 | 显示全部楼层
高手!!

该用户从未签到

发表于 2006-3-12 13:07:00 | 显示全部楼层
<P>高手</P>

该用户从未签到

发表于 2006-3-16 22:58:00 | 显示全部楼层
给大家发一份文章,正好最近也在关注这个什么CCDF,希望对大家有点帮助

【文件名】:06316@52RD_Charaterizing Digitally Modulated Signals with CCDF Curves.pdf
【格 式】:pdf
【大 小】:552K
【简 介】:
【目 录】:
1. Introduction
When are CCDF curves used?
2. What are CCDF curves?
Statistical origin of CCDF curves
Why not crest factor?
3. CCDF in communications
Modulation formats
Modulation filtering
Multiple-frequency signals
Phases affect multi-tone signals
Spread-spectrum systems
Number of active codes in spread spectrum
Orthogonal coding effects
Multi-carrier signals
4. CCDF in component design
Compression of signal by nonlinear components
Correlating the amplifier curves with the CCDF plot
...................


[br]<p align=right><font color=red>+5 RD币</font></p>

本帖子中包含更多资源

您需要 登录 才可以下载或查看,没有帐号?注册

x

该用户从未签到

发表于 2006-3-16 23:10:00 | 显示全部楼层
<DIV>还有一片文章,也给大家看一下</DIV><DIV>Combining CCDF and EVM to assess 802.11 transmitters</DIV><DIV>
Sep 1, 2004 12:00 PM  By Christian Olgaard </DIV><DIV> </DIV><DIV><P>Multicarrier orthogonal frequency division multiplex (OFDM) signals are employed by 802.11a/g to support the highest data rates under the 802.11a/b/g standards, but they pose challenges to the wireless LAN (WLAN) product designer and manufacturer.</P><!--end paragraph--><!--begin paragraph--><P>OFDM signals are characterized by fast-varying amplitudes with high peak-to-average power ratios. To minimize power consumption and yield the highest efficiency, the transmitter's RF power amplifier must be operated with some degree of compression. Finding the optimum operating point is complicated because most power sensors used in typical power meters are not fast enough to track the quickly varying OFDM signals with any accuracy. Moreover, the power meter reading must be gated in order to avoid averaging the gaps between packets.</P><!--end paragraph--><!--begin paragraph--><P>Test instruments that incorporate a vector signal analyzer (VSA) and are tailored to handle 802.11a/b/g signals provide the necessary tools to assess OFDM transmit signals. These instruments do not use power sensors; instead, they downconvert and digitize the complete signal spectrum over a wide bandwidth, capturing the entire signal energy. For instance, LitePoint's IQview and IQflex are tailored for this application. With linear receivers and calibrated gains, LitePoint test instruments provide accurate measurements of peak and average power for all 802.11a/b/g signal types.</P><!--end paragraph--><!--begin paragraph--><P>With such test instruments, two key measurements of 802.11a/g OFDM transmit signals can be made: the error vector magnitude (EVM) and the complementary cumulative distribution function (CCDF) of the transmit output power. EVM is a direct measure of modulation accuracy and transmitter performance, embodying all the transmitter impairments in a single number. The dominant contributors to poor EVM performance are phase and amplitude mismatches, phase noise, and non-linearity of the transmitter. During product development, one must identify these contributors and find ways to reduce them. During production, however, measurement of the EVM is relatively time-consuming and can be minimized in favor of measuring the CCDF.</P><!--end paragraph--><!--begin paragraph--><P>For a well-designed WLAN transmitter, the EVM performance will be limited by compression in the transmitter. With too much compression, the transmit signal quality will be degraded; with too little compression, a more expensive RF power amplifier will likely be required in order to achieve the desired average output power. Simply measuring the output power does not reveal the level of compression in the transmitter, but measuring the output power CCDF reveals the degree of compression and can be directly correlated to the EVM in a well-designed transmitter.</P><!--end paragraph--><!--begin paragraph--><P>The CCDF of the transmit output power is the probability that the signal power is greater than a given peak-to-average power ratio. In other words, if PAR is the peak-to-average power ratio (the magnitude squared of the instantaneous signal normalized by the average power level), and PAR0 is a specific peak-to-average power ratio value, then the CCDF is defined as:</P><!--end paragraph--><!--begin paragraph--><P>CCDF<NUM><SUB>power</SUB></NUM> (PAR) = Pr [PAR &gt; PAR<NUM><SUB>0</SUB></NUM>].</P><!--end paragraph--><!--begin paragraph--><P>In the case of a compressed signal, clipping reduces the peak-to-average power ratios, and the CCDF curve shifts to the left as large peak-to-average power ratios become less likely.</P><!--end paragraph--><!--begin paragraph--><P>An uncompressed OFDM signal approximates a white Gaussian noise process by the central limit theorem as the number of OFDM subcarriers increases. The peak-to-average power ratio for such a Gaussian noise-like signal is itself a random process obeying the chi-square distribution with one degree of freedom. The CCDF for this process is well known, equal t</P><!--end paragraph--><!--begin paragraph--><P>CCDF<NUM><SUB>power (AWGN)</SUB></NUM> (PAR) = exp [- (PAR) ],</P><!--end paragraph--><!--begin paragraph--><P>or, if the peak-to-average ratio is expressed in dB,</P><!--end paragraph--><!--begin paragraph--><P>CCDF<NUM><SUB>power (AWGN)</SUB></NUM> (PARdB) = exp [ - (10^(PARdB / 10)) ].</P><!--end paragraph--><!--begin paragraph--><P>The CCDF corresponding to this Gaussian noise input provides a reference curve the CCDF curve of a compressed signal will fall to the left of this reference, as illustrated by the figures above of a 54 Mbps 64-QAM OFDM signal and a 6 Mbps BPSK OFDM signal. As can be seen, the lower data rate signal is more compressed than the higher data rate signal because it can tolerate a greater (worse) EVM level.</P><!--end paragraph--><!--begin paragraph--><P>By establishing a test where the same data pattern is transmitted with every data packet, measurement of the CCDF can be used to adjust a transmitter's output power to the desired compression level rather than to a specific power level. Measuring CCDF is significantly faster than measuring EVM, making it well suited for production testing. With IQview and IQflex, CCDF and EVM measurements can be made, allowing the EVM to be verified as desired to ensure test reliability.</P></DIV>

该用户从未签到

发表于 2006-3-30 21:26:00 | 显示全部楼层
<P>高</P>

该用户从未签到

发表于 2007-9-23 01:11:00 | 显示全部楼层
谢谢六楼的文章

该用户从未签到

发表于 2007-10-11 11:22:00 | 显示全部楼层
CCDF―――Complementary Cumulative Distribution Function互补累积分布函数,简单的说,就是指正向功率超过其给定门限值的概率.[br]<p align=right><font color=red>+5 RD币</font></p>

该用户从未签到

发表于 2008-8-25 20:36:00 | 显示全部楼层

该用户从未签到

发表于 2009-6-10 20:51:00 | 显示全部楼层

CCDF(Complementary Cumulative Distribution Function)互补积累分布函数

CCDF(Complementary Cumulative Distribution Function)互补积累分布函数
简单的说就是从功率分配的角度描述输出信号质量的函数,可以直观的比较输入输出信号波形质量

的线性化效果,这是在类似增益、功率直接测量图上无法表现的。

签到天数: 9 天

[LV.3]偶尔看看II

发表于 2018-10-9 17:47:36 | 显示全部楼层
很好的文章,谢谢
高级模式
B Color Image Link Quote Code Smilies

本版积分规则

手机APP| 小黑屋|Archiver|52RD我爱研发网 ( 沪ICP备11014270号-1

GMT+8, 2018-12-13 03:29 , Processed in 1.545861 second(s), 32 queries , Gzip On.

Powered by Discuz! X3

© 2001-2013 Comsenz Inc.

快速回复 返回顶部 返回列表