无线网卡测试!!!

孤鹏掠影

我用 IQ flex 测试无线网卡时,其中有一项 叫 EVM 的很难Pass,而且多数都是高通道的;在实测的时候总感觉 throughput 不够稳定,而且也比一般的差一点.
请问这个参数是什么意思,主要受那部分电路的影响? 先多谢各位了!!!

maxchung

EVM&#63870;測結果&#63855;明&#63930;問題，但與其他&#63851;&#63849;的測&#63870;結果組合，可有助於確定發射信號減損的原因︰–IQ 失衡( IQ imbalances )。–相位雜訊( phase noise )。–寄生訊號與瞬態效應( spurious signals and transient effect )。–信號壓縮效應( effect of signal compression)。&#8226;EVM&#63870;測結果&#63855;明&#63930;問題，但與其他&#63851;&#63849;的測&#63870;結果組合[em01][br]<p align=right><font color=red>+3 RD币</font></p>

minggong88

首先說明EVM的概念:EVM錯誤矢量幅度,表示在IQ星座圖上,信號偏離正確位置的大小,使得我們接收時不能分辨出來.我測試的4965intel的無線網卡,EVM的指標是小於-25dB.
EVM主要受RFIC裡產生的SIN和COS波形的正交性影響,,還跟POWER的大小有關.POWER大了,EVM會變壞.有時PA就會有這樣的問題.[br]<p align=right><font color=red>+3 RD币</font></p>

孤鹏掠影

谢谢两位!
2楼的大侠,能不能具体的说明EVM 的测量结果主要说明了什么问题啊!

windblow1981

我以前在另外一个版发过有关EVM测量的文章,希望对你有帮助
这里再发一次

【文件名】:0774@52RD_8 Hints for making and interpreting EVM measurement.rar
【格　式】:rar
【大　小】:322K
【简　介】:
【目　录】:

Introduction
Error vector magnitude (EVM)
measurements can provide a great
deal of insight into the performance
of digital communications
transmitters and receivers. With
proper use, EVM and related measurements
can pinpoint exactly
the type of degradations present
in a signal and can even help
identify their sources.
Primarily a measure of signal
quality, EVM provides both a simple,
quantitative figure-of-merit
for a digitally modulated signal,
and a far-reaching methodology
for uncovering and attacking
the underlying causes of signal
impairments and distortion. EVM
measurements are growing rapidly
in acceptance, being already
the required modulation quality
measurement in such important
technology standards as 3GPP
W-CDMA and IEEE 802.11a/b/g
WLAN, and they are poised to
appear in several upcoming
standards.
This application note provides
useful tips that will assist in accurately
making and understanding
EVM measurements.

孤鹏掠影

谢谢啦！, 谢谢啦！

telepower888

[em08][em08]

wolfswvrd

我想你的throughput主要TX不好吧！

孤鹏掠影

谢谢各位！
现在问题已经解决了，主要是RF IC的电源不够干净，带有较多的杂波，我换了一个较好的的电源管理IC后，EVM一般都降低了 2个dBm左右，还有VLO还适当的调低了一点点！[em01]

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