6139+77518 phase error 和频偏大的问题，求高手指点

fengshi004

把6139的那个4.7uF的对地电容拆掉，看一下情况！

xgm0315

请教一下楼上的高手：6139的那个4.7U电容会影响什么？？

keithen

对于搂主的频率偏差问题，请看看是不是整体偏移，如果是整体偏移的话，解决起来非常容易，如果是上下偏移比较大，正负都超标，那就要在LAYOUT上面下功夫了。

hunterzhao

最有效的方法也是唯一的办法，就是直接改板，将TC与PA分开，再调试一个月你就会明白改板是必须的了。

hunterzhao

6139的制成问题，6139在设计上没有6129那么成功，6139的收发隔离比较差，所以必须使用外加屏闭盖的方式增强收发隔离。[em04]

barochen

1.After you change the Resistor to 10k, the swing of VAFC will be much lower. At the same time, if you consider the VAFC input impedance, you will see the swing of input will be much lower at the same time. that's the root cause why the phaser error will be better


2. What's the VAFC? I have not do MTK platform. If I am corrrect, it should be Auto Frequency Control. Now you changed the control signal, of course the frequency error will be worse.


I have some proposals to you:
1. change to resistor to 1k Ohm
2. add two capacitor in VAFC, one is 15pF, another is 39pF
3. check the VAFC layout very very carefully, I suspect there is some interference to this line

Good Luck to you![em01]

cosqingcao

这已经是一个老问题拉!  TC 和PA一定要很好的隔离,如果没有隔离的话,在HB  上加一个LPF试下,并加到地的电容,LDO最好也动一动.

sam985111

如果能解决这个问题,所有做MTK的都会感谢你的