Smooth corner in the technical sense

PCBWING

New Member

• Mar 26, 2012

• #1

Hi, guys
I received an advertisement E-mail from India today. I found it gives some examples of PCB layout and this is one of them. Please have a look, Why would they point that is " smooth corner"? Shouldn't it has some special meaning？

Thanks in advance!
PCBWING
View attachment 62691

 

duffy

Well-Known Member

• Mar 26, 2012

• #2

You get reflection off sharp angles up in ghz speeds.

 

PCBWING

New Member

• Mar 27, 2012

• #3

duffy said:

You get reflection off sharp angles up in ghz speeds.

Click to expand...

Hi duffy, Is this "off" actually occurred, or only the theory conjecture? Ask about this is cause I got a "smooth corner is useless" in several days past.

 

K

kubeek

Well-Known Member

Most Helpful Member

• Mar 27, 2012

• #4

https://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=SCAA082&track=no

 

duffy

Well-Known Member

• Mar 27, 2012

• #5

It's in section 2.5 of that link kubeek helpfully provided.

I've never actually got a reflection, that may be a myth, or come into play at higher frequencies than I work with. I have had problems passing FCC tests, and this is part the lore of things to do to minimize harmonics. I can't even say for sure that it actually works there - when we are at that stage of the game we are adding ferrites, moving cables, etc. rather than re-routing boards.

 

Last edited: Mar 27, 2012

PCBWING

New Member

• Mar 28, 2012

• #6

Thanks, I see. It seems that they obtained results through the test. BTW, Does that "adding ferrites" mean a filter or a electromagnetic delay line？

 

duffy

Well-Known Member

• Mar 28, 2012

• #7

You clamp a ferrite around a cable. The cables leading to a board act as the antennas in radiated emissions tests when the board is in an enclosure.

 

PCBWING

New Member

• Mar 28, 2012

• #8

Ferrite

Did you mean “ferrite coated connection place between cable and board” ?

View attachment 62763

 

duffy

Well-Known Member

• Mar 29, 2012

• #9

The picture is correct, you thread cables through those ferrites, or snap the ferrite around the cable, and it reduces the high frequency spectral signature.

There are other approaches, the ferrite is more of a last-ditch option when you are at the test facility and your machine is failing emissions.