Ground plane, power plane and antenna design

[vreg]

Hi,

Can someone please explain the need for ground planes, power planes (and any other planes) in PCB design.

I am familiar with basic PCB design in Eagle using two layers (top and bottom), but I have never required using ground/power planes.

Basically, I have only designed shields for my arduino based projects - I guess ground/power planes are required if your PCB has components like micro-controllers?

Also, can I design a patch antenna using Eagle (using just one layer) - Again, I have seen designs that include a ground plane but am not sure why that is required.

 

[volker@muehlhaus]

Yes, power and ground planes simplify the routing. And thinking of high speed design where series inductance matters: they also provide a lower inductance path for supply than routing individual lines across the PCB.

Patch antenna by design requires a ground plane on the back, and this is what causes the directed antenna pattern. But there are other antenna designs with more omni-directional radiation where the radiator is over an empty non-GND area. https://muehlhaus.com/support/mwo-appnotes/awr_mwo_antenna_868_915

 

[marce]

Return paths for signals especially above 1MHz

 

[vreg]

How do you add a ground plane to your design?

In Eagle, there is only an option to select the top/bottom layer on which you want to route your signals...

Thanks.

 

[volker@muehlhaus]

How do you add a ground plane to your design?

Draw a copper rectangle and use it as ground.

 

[hobbyckts]

As you are going to use a single layer creating ground plane somwhere middle of the PCB will be tough. So make a copper line or strip at the edge of the PCB and connect the ground line to it. This could provide the ground plane which you asking for. Better leave the strip disconnected.

 

[vreg]

Thanks for your replies.

Is it possible to add a separate ground plane (In a PCB CAD software like Eagle) ?

Also what difference will I get in performance between a separate gnd plane and a copper rectangle on the same plane?

 

[volker@muehlhaus]

Also what difference will I get in performance between a separate gnd plane and a copper rectangle on the same plane?

Identical, it's the exact same thing. A ground plane becomes a ground plane by using it for ground return. For RF, we use solid metal areas. If your software is smart, it will create cutouts when other nets pass through a ground plane, but for RF we want to keep is solid anyway.

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So make a copper line or strip at the edge of the PCB and connect the ground line to it. This could provide the ground plane which you asking for. Better leave the strip disconnected.

For sure, this will not work for patch antenna ground plane.