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EMC good practices

Rajinder

Jan 30, 2016
568
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Jan 30, 2016
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568
Hi
I was wondering if someone could help me with the following EMC and PCB layout questions:

1. Why is it good to have a separate layer dedicated to the GND? Is it because it is a low inductance/resistance path to ground? i.e. less voltage spikes?
2. Are track lines meant to be short as possible because the longer the track the more it radiates as a antenna?
3. If I had a 30mm track, what would I need to change for a 1MHz square wave compared to a 5GHz square wave on the same length of track? What modifications would I need to make?
4. I am not sure what ground current loops are and how to reduce the effects of these.
5. When choosing a decoupling capacitor say for example a 100nF on a IC (between VCC and 0V) close to the IC pins. Do I use Xc = 1/(2*PI*F*C) as the formula? For the frequency (is that the frequency of the signal I am looking to reduce?) Also should I aim for a value of XC to be as low as possible but not 0, as 0 would be a short between VCC and 0V?
6. Why is it a good idea to have the VCC and GND layers (on a 4 layer PCB), back to back?

Thanks in advance
 
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