EMC and PCB

[GDSU]

Hi all,

i'd like to know that is there any software out there can do the
EMC performance simulation of a PCB board? EMC is not that easy to
achieve especially for high frequency products. however designing PCB,
sending to PCB house, EMC troubleshooting, redesigning PCB, the cycle
is too time consuming and costly. so i want to know is there any
software that let you design your PCB and run a few simulations to get
the rough EMC performance result? just like SPICE for circuit design?


Best regards
GDSU

 

[Bill Sloman]

Hi all,

i'd like to know that is there any software out there can do the
EMC performance simulation of a PCB board? EMC is not that easy to
achieve especially for high frequency products. however designing PCB,
sending to PCB house, EMC troubleshooting, redesigning PCB, the cycle
is too time consuming and costly. so i want to know is there any
software that let you design your PCB and run a few simulations to get
the rough EMC performance result? just like SPICE for circuit design?

The software exists - the proximate cause of my being made redundant
in 1991 was the decision of my boss to leave Cambridge Instruments and
start a company selling electromagnetic field simulation software and
consultation in EMC problems.

Whether it is much use is another question. Simple inspection of a
layout seems to work pretty well if you think about the current loops
you are setting up. Simulation software isn't much use if you don't
understand what it is telling you.

 

[Rene Tschaggelar]

Hi all,

i'd like to know that is there any software out there can do the
EMC performance simulation of a PCB board? EMC is not that easy to
achieve especially for high frequency products. however designing PCB,
sending to PCB house, EMC troubleshooting, redesigning PCB, the cycle
is too time consuming and costly. so i want to know is there any
software that let you design your PCB and run a few simulations to get
the rough EMC performance result? just like SPICE for circuit design?

IMO, there is none.
As long as there are GND symbols to be placed, these GND's are identical.
There is no current through GND and no SuperGND, nor can GND couple
or radiate. Those who do EMC designs with success do it with guidelines,
a lot of thinking and guts.
That's also why these specialists are well regarded in the company and
well paid.

Rene

 

[R.Legg]

The software exists - the proximate cause of my being made redundant

in 1991 was the decision of my boss to leave Cambridge Instruments and
start a company selling electromagnetic field simulation software and
consultation in EMC problems.

Whether it is much use is another question. Simple inspection of a
layout seems to work pretty well if you think about the current loops
you are setting up. Simulation software isn't much use if you don't
understand what it is telling you.

A refreshing admission from someone involved in the field.

When I start voicing similar opinions, based on experience with both
situations, I find it actually hurts my credibility.

It's funny how some new SW applications can be loudly championed by
people with little or no experience in the techniques being replaced
or augmented.

RL

 

[Rene Tschaggelar]

IMO, there is none.
As long as there are GND symbols to be placed, these GND's are identical.
There is no current through GND and no SuperGND, nor can GND couple
or radiate. Those who do EMC designs with success do it with guidelines,
a lot of thinking and guts.
That's also why these specialists are well regarded in the company and
well paid.

There indeed are packages that are able to calculate coupling, eigenmodes
and the lot. They involve a 3D editor and require you to model each occurence
of interest. Beside the 20k$ per year per seat they require you to work
moreless fulltime with them otherwise you won't be able to use them to their
fullest.
The guidelines, thinking a lot and intuition approach is possibly faster.
Yes, the autorouter are not up to that. It is called manual routing.

Rene

 

[Syner]

Unlike many other design issues, EMC is not an area where it is
possible to list a setof rules. EMC compliance cannot be guaranteed
by design; it has to be tested.
for example some design rules

Identify the Noise source
A very important general rule is that all types of noise should be
handled as close to the source as possible, and as far away from the
sensitive parts of a circuit as possible.

The Path to Ground
The basic idea behind many EMC design techniques
is to control the path to ground for all signals, and make sure that
this path is away from signals and circuits that may be disturbed.

System Zones
Handling every EMC problem at once is a very complex task. It is
therefore a good idea to split the system into smaller subsystems or
zones, and handle these individually. The zones may, in some cases,
only be different areas of the same PCB. The important part is to have
control of what happens inside one zone, and how the zones interact.
For each zone, the designer should have some idea about what kind of
noise the zone may emit, and what kind of noise it may have to endure.

RF Immunity
Long I/O and power cables usually act as good antennas, picking up
noise from the outside world and conducting this into the system. For
unshielded systems, long PCB tracks may also act as antennas. Once
inside the system, the noise may be coupled into other, more sensitive
signal lines. It is therefore vital that the amount of RF energy
allowed into the system be kept as low as possible, even if the input
lines themselves are not connected to any sensitive circuit.

other aspects are also important .such as
ESD and Transients
Power Supply, Power Routing and Decoupling Capacitors
PCB Layout and Grounding
Shielding

syner