Frequency Err 到底怎么调整？

wishiloveu · 发表于 2005-12-23 09:07:00

这个一般都是公司买了设备之后，进行的售后培训，这个一般是他们的售后技术工程师，或者头衔是什么应用工程师来做的，如果是报名参加的那种培训班很贵，是由Agilent的培训讲师来讲，这些培训讲师平时也对他们员工进行培训的，大概一个人为期3天的培训需要5000RMB把。。如果能说服公司出钱参加，当然是再好不过的了。。[em01]

cuijw · 发表于 2005-12-23 09:38:00

Agilent工程师大学不错的，现在开始发毕业证、结业证了了，分为多个范围、3级，有点类似大学的制度了公司付钱培训当然好，不过能让Agilent付钱更好办一些（老板通常都比较省钱），也不是特别难，看你的业务量了

xdtony · 发表于 2005-12-23 10:31:00

<DIV class=quote>以下是引用Challenger在2005-12-21 13:48:32的发言：

我也不是专家，呵呵。我参加的是Agilent的培训，测量相位/频率误差的过程是这样的：
被测信号先送至解调器，解调器按照预设的与被测信号匹配的参数对信号进行解调，得到调制信号数据，然后由仪器自身的数学方法再按照同样的调制参数对数据进行调制，得到参考信号。将被测信号与参考信号进行比较就可得到相位误差矢量，该矢量的平均斜率即为频率误差，而除去频率误差后的短时相位变化定义为相位误差（包括RMS或Peak）。

+5 RD币</DIV>

当初我们公司买了一批Agilent的设备，他们也安排我们参加了各种仪器的培训，感觉比较通俗易懂，只有一些打印出来的PPT，问他们要电子版的不肯给。整体内容还是比较初级，适合入门级。楼上这位仁兄提到的测试方法在附件中都有提到，大家可以参考一下。
简介:Agilent 测试FE、PE、PVT、ORFS等的一些方法，还提到了这些测试项指标不理想时可能的原因，比较有借鉴意义。
格式:pdf
大小:802K
[br]+5 RD币

Lupos · 发表于 2005-12-26 11:30:00

谢谢楼上的[em14]

sirbj · 发表于 2006-1-14 10:24:00

1．关于手机的AFC自动频率控制，我有一个猜测，拿出来 和大家讨论一下。我认为手机在idle状态，会检测基站的C0的TS0时隙上的FCCH逻辑信道，这个信号是3比特头，142全0，3比特尾，8.25保护比特组成的。基带bb将这个 解调出来，如果频率没有完全校准，那么基带输出将是一个甚低频的信号，基带利用这个信号计算出频率误差，确定AFC的值，然后利用bb中的DA(其输出就是AFC模拟信号了)去调整26M的RF外部晶振，从而完成AFC过程。如果这一推测正确，那么奇怪的就是1）手机岂不又计算和基站（或8960等测试仪器）之间频率差的能力？2）手机怎么利用解调出来的FCCH信号计算频率误差，类似软件pll？2．关于手机检测相邻小区发射能量，我想和大家讨论一下，1）检测相邻小区发射能量，是检测相邻小区的FCCH还是其他信道？？2）idle状态下，手机除检测本基站的ts0外（如果SDCCH8逻辑信道映射方式，还会检测ts1），手机在什么时候去相邻小区的能量呢？由于小区之间并不同步，如果有某一个相邻小区与本小区的FCCH时间重叠或者基本重叠，那结果不是会漏掉这个相邻小区？或者是网络配置的时候会避免这种现象的发生？有资料说手机并不和相邻小区同步，因此会搜索相邻小区的c0的8个时隙，以找到ts0并且测量其能量。那这样和可能和本小区bch信道的监测发生时间上的冲突亚！3）在通话状态，手机解调TCH时隙，好像此时不再检测bch(c0 ts0时隙)。但是好像手机还是会检测相邻小区的能量并向基站报告，那么在通话状态下，手机又是什么时候检测相邻小区的能量呢？[br]+5 RD币

RFlw · 发表于 2006-1-15 10:27:00

1, AFC_DAC will control crastal oscillator, To be mentioned, AFChas been calibrated and save in ROM or register map, so Crastalosc will be locked pretty well, no problem.
2, For GSM, TX PLL is KEY since no amplitude info needed, only Phase. Alot of improvement have been made in recent years, such as Wide-bandPLL, Fractional_N_Offset_PLL to improve the freaquency and phaseaccuracy.
3, No control needed from Base Station, guranteed by transceiver design.
[br]+5 RD币

sirbj · 发表于 2006-1-15 11:49:00

我知道 DAC控制TCXO，但是怎么控制，软件肯定有个算法。算法需要知道输入，然后输出控制信号把？？？请在说具体点把，谢谢！

RFlw · 发表于 2006-1-17 01:39:00

OK. The concept is as follows:
a, Xtal OSC coarse tuning ---stored in ROM, life time
b, Xtal OSC fine tuning--to find the first starting min err point
c,MS received Broadcasting info, specifically FCB (Frequency correction Burst)
d, Base band calcualte freq offset
e, Send offset correction to transceiver through SDI or DigRF interface, whoever is used in design
f, Transciever take and write control words to AFC DAC,
g, Done

Sorry not able to provide BB algorithm, hopefully it is enough to help understanding!!
[br]+5 RD币

hehehaha · 发表于 2006-1-18 10:50:00

对此了解的也不多。手机对FCCH（freqence correction channel) 及 SCH(synchronization channel)进行DSP解析，得出几个数据：power ,TOA,angle,snr。根据以上几个值，利用一定的算法，如kalman,LQG,等等，经过几次逼近到或者修正所要的AFC VALUE。关于DSP如何从接收的CH里，得到，信道功率，角度，信噪比，等就不得而知了。[br]+3 RD币

hehehaha · 发表于 2006-1-18 10:54:00

接上，一个好的AFC算法的平台，对于手机NSIG下，AFC的校正是多余的。TI的就不怎么样，default value会导致注册不上网络。[br]+3 RD币

jsyccxj · 发表于 2006-1-18 12:40:00

请教楼上的，我们做TI平台的。电话呼通率低，尤其是用联通卡或信号差的时候。还有电话打不进打不出的情况。是不是AFC的值导致的呢？

hehehaha · 发表于 2006-1-18 14:12:00

楼上的，据我分析，你所说的与AFC无关，AFC只会引起注册网络偏慢，或者有可能注册不上。但是只要注册上了，MS与基站每个超帧都会进行同步的动作。因此频率肯定是对的，排除AFC的问题。如果同步不上，就是掉网了。[br]+5 RD币

wujason · 发表于 2006-1-19 09:50:00

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BORDER-TOP: #ebe9ed; BORDER-LEFT: #ebe9ed; WIDTH: 54pt; BORDER-BOTTOM: #ebe9ed; BACKGROUND-COLOR: transparent" width=72></TD><TD #ebe9ed; BORDER-TOP: #ebe9ed; BORDER-LEFT: #ebe9ed; WIDTH: 54pt; BORDER-BOTTOM: #ebe9ed; BACKGROUND-COLOR: transparent" width=72></TD><TD #ebe9ed; BORDER-TOP: #ebe9ed; BORDER-LEFT: #ebe9ed; WIDTH: 54pt; BORDER-BOTTOM: #ebe9ed; BACKGROUND-COLOR: transparent" width=72></TD><TD #ebe9ed; BORDER-TOP: #ebe9ed; BORDER-LEFT: #ebe9ed; WIDTH: 54pt; BORDER-BOTTOM: #ebe9ed; BACKGROUND-COLOR: transparent" width=72></TD></TR><TR 15.75pt" height=21><TD class=xl22 #ebe9ed; BORDER-TOP: #ebe9ed; BORDER-LEFT: #ebe9ed; BORDER-BOTTOM: #ebe9ed; HEIGHT: 15.75pt; BACKGROUND-COLOR: transparent; mso-ignore: colspan" colSpan=10 height=21>然后利用bb中的DA(其输出就是AFC模拟信号了)去调整26M的RF外部晶振，从而完成AFC过程。</TD></TR><TR 14.25pt" height=19><TD #ebe9ed; BORDER-TOP: #ebe9ed; BORDER-LEFT: #ebe9ed; BORDER-BOTTOM: #ebe9ed; HEIGHT: 14.25pt; BACKGROUND-COLOR: transparent" height=19></TD><TD #ebe9ed; BORDER-TOP: #ebe9ed; 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sirbj · 发表于 2006-1-19 21:25:00

26M可以细调，因为26M的时钟误差要求在0.1ppm以内，所以需要实时的调整。一般GSM手机bb都会有一个da专门负责输出afc（自动频率控制信号）这个信号是个模拟信号，可以控制26M作细调！[br]+3 RD币

hehehaha · 发表于 2006-1-20 08:27:00

楼上的，更正一下，一般26M的SPEC上都是+/-10PPM左右。在系统中，实际26M的精度为：GSM，0.1/（900M/26M）=2.3ppb DCS=1.1ppb左右。精度非常之高，超出一般人之想象。[br]+3 RD币

ldhui · 发表于 2006-1-20 18:39:00

35楼的,你理解也许有误,GSM和DCS要求0.1ppm,26M也应该是0.1ppm.

hehehaha · 发表于 2006-1-20 20:27:00

楼上的兄弟，你再把PLL原理搞搞清楚，就知道了。

RFlw · 发表于 2006-1-22 22:12:00

The requirements for Xtral for both GSM and DCS should be same.

Let 's see the case as follows':
a) VCO runs at 4 GHz
b) VCO will be divided by 2, LO used for DCS band
c) VCO will be divided by 4 -> LO is used for GSM band
d) PLL output frequency will feed back to Phase Dectector/Charge Pump
e) Reference freq comes from 26 MHz Crystal Oscillator

so the reference freq is same, the difference (GSM and DCS) is the LO divider.
I would conclude that the requirements for Xtal Oscillator are same.
+3 RD币

[此贴子已经被feel于2006-1-24 0:01:49编辑过]

hehehaha · 发表于 2006-1-23 08:08:00

快过年了，在论坛上还比较热闹，大家都没有赶回家吗？
看来此问题有存在着很大的异议,楼上的看来也是误解了。
[upload=jpg]UploadFile/2006-1/06123@52RD_pll.jpg[/upload]

Fvco=Fref/R*N[br]+3 RD币

hehehaha · 发表于 2006-1-23 08:11:00

当Fvco=0.1ppm时，则Fref=?中学题，大家应该都会解。详细我就不讲了。这里输出功式比较麻烦。[br]+3 RD币

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[讨论] Frequency Err 到底怎么调整？

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