HighSpeed PCB--> Power-Supply Bypassing

[Luca_Romano]

Hello everybody,

I'm collecting info with regard to HighSpeed PCB production methods. I would like next to build a PCB including a bluetooh(2.4 GHz) and a WIFI(5GHz) modules.
I have read something regarding both "power-supply bypassing" technique to minimize the noise and the ground plane. Is there someone of you that can help me to understand the most critical difficulties in a RF/microwave PCB layout realization?
Thanks a lot,
regards,

Luca

 

[PRJI]

Hi Luca,

Do you have any specific question?

Thanks
Prajith

 

[Luca_Romano]

Hello Prajith,

thanks for your interest in my post. I would like to know generally and in wider terms how to make a PCB that includes RF/microwave devises (bluetooh and wifi modules).
1)How to get a routing;
2)How to use the ground plane;
3)How to use mechanical shields.
Thanks a lot
Luca

 

[ArticCynda]

You're talking about bluetooth and wifi modules. In that case, the module takes care of all the high frequency issues, and the control lines to these modules are generally low frequency buses (I²C, SPI, UART etc.). These don't require any specific high speed PCB design guidelines. Throw in a 100n decoupling cap for each power pin and a 22µ - 100µ electrolytic capacitor near the module and you should be good to go.

 

[FvM]

In that case, the module takes care of all the high frequency issues

Yes. The RF application suggests this design features nevertheless:
- have a continuous ground plane if feasible (4.layer PCB)
- calculate correct micro strip geometry for antenna connections
- use bypass capacitors according to module specifications

What do you mean with mechanical shields?

 

[Luca_Romano]

Hello FvM, ArticCynda

thanks a lot for your replies and good suggestions.

Yes. The RF application suggests this design features nevertheless:
- have a continuous ground plane if feasible (4.layer PCB)
- calculate correct micro strip geometry for antenna connections
- use bypass capacitors according to module specifications

What do you mean with mechanical shields?

with mechanical shields i mean metallic packages (conductive and/or magnetic materials) used to prevent EMI from escaping the system.

Thanks and regards,
Luica

 

[ArticCynda]

[quote="Luca_Romano]with mechanical shields i mean metallic packages (conductive and/or magnetic materials) used to prevent EMI from escaping the system.[/quote]Shields can be best connected to ground with a few capacitors so that any noise will be shorted to ground. Do not connect it to ground directly to prevent large currents from flowing in case the shield is accidentally shorted with another part (i.e. because of a loose wire, a screwdriver etc.)