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EMC/EMI - PCB Designing using Allegro 15.7

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jack_pcb

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EMC/EMI

Hii alll ,
I am New in PCB Designing using Allegro 15.7 .
Can any body please help me to know , wat is EMC and EMI and in PCB wat are the things which affects it ,

Thanks in Advance
 

DavidReina

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Re: EMC/EMI

EMC stands for Electromagnetic compatibility, and henry ott define it as: the ability of a electronic system to work properly in its intended electromagnetic enviroment, and to not be a source of pollution to that enviroment. You can find a lot of info on this on the web, If you want your designs to be shiped and work in the US you should comply with the FCC sregulations.

EMI stands for Electromagnetic Interference, and as the name describe it, is noise created by an electromagnetic coupling between 2 or more electronic systems, crosstalk is an example of it (but crosstalk is between 2 Transmission lines). Also you can find a lot of information of EMI in the web.

hope this helps
 

biff44

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Re: EMC/EMI

Well, there is surely some magic involved in proper EMC design of a PCB. RF and Microwave signals like to radiate out into free space. As a board designer, you often have to try to stop those signals from radiating. This is often a requirement of your government's regulations, such as FCC or ETSI rules.

Things that make a signal radiate:
Long lines (more than a few cm's) between components.
A broken ground plane (a ground plane with traces that cut through it, forcing any ground currents to meander around in loops).
Poor decoupling (not using microwave decoupling capacitors between an RF chip's DC power pin and the board ground. Also, not having a good ground via for such capacitors, or placing them too far from the offending component).
Adding RF circuits (like lowpass filters) between a transmit output and an antenna, but not being careful to con the reflected harmonic power.
Allowing wires/ribbon cables to move from inside of a shielded enclosure to the outside without appropriate EMI filtering.
Poor ground attachment (often too much length) between the shield on a coaxial connector and the ground plane on a board.

Those are some of the bigger issues.

Rich
www.MaguffinMicrowave.com
 

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