Relation between PCB trace width and number of layers

[newbie_hs]

I need to design a PCB for RF Application.
The board contains jsut 4 sma connectors .Connected as shown below.

The frequency of operation is 20Ghz. Trace impedance should be 50 Ohm.Current 1A
Initially I decided to use 2layer board.Then I was told to use 4 layer board .The reason was told is it will help to reduce the trace width.

May I know is there any relation between PCB trace width and number of layers

 

[FvM]

You are creating planar, coplanar or embedded transmission lines. Correct trace width for 50 ohm impedance is different for each transmission geometry.

I don't see a general advantage in using multiple layers for RF transmission lines. Assume you achieve highest power rating with basic planar geometry (two layer).

 

[barry]

For microstrip,the impedance is directly related to the distance between a trace and ground plane. In other words, for a given impedance, a thinner pcb will require a thinner trace, but adding layers does nothing.

HOWEVER, if you use stripline, i.e., 3 layers, you can use a thinner width.

Look at this.