射频线阻抗控制相关问题请教射频高手

不好意思，用英语描述问题可能好一点，希望知道答案的大虾帮忙回答一下，中英文均可，不胜感激！
任务比较紧急，希望大侠能解释清楚一点！
I have a question about the BT transmission trace issue( about impedance control) to ask RF engineer :
(1)Information:
phone stackup 1-2-1, lay 1-->top side for component placement; layer2 and layer 3-->signal and power supply routing; layer 4 -->keymat trace
and some other trace(a little)
(2)question desctription:
The stripline is from BT chip to BT antenna feed point, it is in layer2 ,and the reference grounding layer is layer 3 and layer 1. I will do the
impedance control to this trace. its' Characteristic impedance is 50 ohm. So i need to calculated its' width. After calculation ,the width is 90um.
(3) question:
I routing this stripeline in layer2, meanwhile i required the layer3 and layer1 related area(above and below the stripeline) should have integrated
grounding for this trace. But you know , our phone just totally have 4 layers. There are many traces should routing in layer 3 and layer 2.
In layer 2 they can meet me clearance and grounding requirement , but in layer 3 ,it can not meet the integrated ground requirement. There are
many traces will across it vertically. I think this can not ensure the 50 ohm impedance requiement. meanwhile it will bring other interferer signal.
So what is your opinions and suggestions about this issue? The impedance can in my control if the layer 3 are not integated ground?
If yes ,how to achieve it ? If not , how did i resolve this issue?

,还是翻译成中文比较好理解点。

基本知道啥意思，不过四层板比较少了，一般至少都得六层。四层板子最麻烦的就是调试天线，同时还带来很多莫名其妙的问题。
不推荐用4层板，除非是接口板。