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EMC and PCB

Discussion in 'General Electronics' started by GDSU, Aug 19, 2003.

  1. GDSU

    GDSU Guest

    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
     
  2. Bill Sloman

    Bill Sloman Guest

    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.
     
  3. 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
     
  4. R.Legg

    R.Legg Guest

    The software exists - the proximate cause of my being made redundant
    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
     
  5. 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
     
  6. Syner

    Syner Guest

    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
     
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