Re: RF PCBs


GORDONJ REASON <gordonj.reason@...>
 

Thankyou Andy .............

Copper Pour ........... 

I have never heard that expression before , even in my 45 years in pro electronics .... 

I do recall , having problems with an rf amp once , that was oscillating , and very livley .... and not for any obvious reason ...

When I measured the PCB , it was a quarter wavelength in length ...... drilling some extra holes to make grounding via's , solved the problem ..... a point to bear in mind , for frequencies , above 1.3 ghz .... 

Never stop learning eh? 


On 05 June 2016 at 13:30 "Andy Talbot andy.g4jnt@... [ukmicrowaves]" <ukmicrowaves@...> wrote:

 

 

A coper pour is where all remaining non track areas of a PCB are filled with copper - automatically generating the specified guard gap between it and the existing tracks. vias are used to connect it to the ground plane proper.  Its a function built into decent PCB layout packages.   I've used it on two layer boards to generate the lower ground plane while still having a (very) few connecting tracks on the underside

I suspect that if the gap between in an a microstrip track  is too small, it will unduly influence the impedance of the  transmission lines when used at uWaves; but as you'e only interested in < 100MHz, that won't matter.   May help decoupling, but 100MHz is DC these days,  to all intents and purposes.   So won't make much difference

Andy  G4JNT

On 5 June 2016 at 13:06, GORDONJ REASON gordonj.reason@... [ukmicrowaves] <ukmicrowaves@...> wrote:
 

 

I would certainly have a ground plane layer , where it is accessable , then it's usefull to decouple some components that may require additional decoupling / modding .....

and what is a copper pour ?

On 05 June 2016 at 09:31 "richard@... [ukmicrowaves]" <ukmicrowaves@...> wrote:

 

 

Hi folks


I'm looking for some advice. I'm playing around with an RF pcb design for a piece of test equipment. It's a 4 layer FR4 board. The stack is RF + digital, GND,  3v3, Signal2 (no RF). The highest freq will be 100 MHz. It's not hugely sensitive (transmits only ~100mw). Is is worth having a via-stitched copper pour on the top layer? Will actually make any difference?  Could it actually make things worse.There seems to be a lot of "lore" about but I can't find any hard facts.


Amusing anecdotes (and even facts) welcome.


73 Richard G3CWI



 


 


 

 

 

 


 


 

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