Re: 7. An overview of wireless alarm system techniques (part 2 of 2)..

[Crash Gordon® <NONE@xxxxxxxx>]

Now you're an expert on FCC & UL testing procedures as well huh?
Sheesh man, you'd be interesting if you knew what you were on about, =
since you don't  you're a freekshow, you know that don't you?

<-pull@shoot> wrote in message =
news:6rek711j4so7q8buu1gk733qb0mtna480b@xxxxxxxxxx
>=20
> In order to avoid confusions i like to approach some "hidden" FCC
> requirements.
>  Why hidden?
>  Because they are not apparent (?) but unavoidable during the
> manufacturer design phase.
>  So lets try to go on that hidden part ----> certification of the
> designed equipment...
>  It's a manufacturer concern but you have to know what is exactly
> involved with that, in order to avoid confusions generated smoke by
> some so called professionals (?).
>=20
> Before i can handle that i need to give some context information.
>=20
> Receiver types (simplified):
> Regenerative, single and double conversion maybe used. All have in
> some sense small "transmitters" build in due to the principle in the
> case of the super regenerative type or due to the oscillator in the
> other types.
> The transmitted signal generated is the unwanted radiated part of the
> receiver system and must be suppressed below a certain level in order
> not to disturb other equipments in the vicinity.
>=20
> uC Processors (simplified):
> At the actual state of art it's easy to use a micro-controllers to do
> the required functions in the sensors and at the control panel.
> Those micro-controllers (or similar devices) use a clock. Clocks
> operate on a frequency and are as such a small transmitter.
> Here again that unwanted radiated signal must be suppressed below a
> certain level.
>=20
> Regions:
> The world is divided in regions having each they're own regulations.
>  Region 1 (part): In the European community you have EU regulations
> that are individually integrated in the different member states.
> Region 3 (part): The US, Canada, ++ are in that region.
> Let's keep it like that, it's incomplete but sufficient for the
> explanation.
> Regulations in those regions are close to each other but with some
> small(?) differences between each other subject certification
> requirement (and frequencies assigned to wireless systems).
> The differences have no real impact on what will be stated hereafter.
>=20
> ElectroMagnetic Compatibility of the equipment's:
>  ElectroMagnetic Compatibility (EMC) is a requirement.
>  A lot can be said about EMC but it's in fact a requirement that tend
> to keep compatibility between different equipment's using electronic
> circuits inside.
>  It specify for all types of equipment (not only wireless system but
> also dishwashers and + using uP's):
> - the maximum limit of internal generated "unwanted" signals
> - the minimum of un-sensitivity (required to avoid "unwanted" radiated
>    signals form other equipment's) to disturb the operation.
> The difference between unwanted transmissions and un-sensitivity is
> called to be the immunity margin, the first being lower than the
> second of course.
>=20
> Transmitter regulation:
> Complex specifications that measure in essence side bands, harmonics,
> and frequency stability.. to mention only a few.
>=20
> Wanted versus unwanted signals:
> Note the big difference between "wanted" an "unwanted" signal.
>  The transmitted frequency in a transmitter is "wanted" signal, the
> emissions generated by the other internal electronic circuits are
> "unwanted".
>  In a receiver the wanted signal is the receive frequency of the
> wireless alarm system, the unwanted all the others (oscillators).
>=20
> General concept of certification:
> It's the proof that the equipment satisfies the regulations.
> Each design has to undergo test in open air or in an open air like
> environment, called anechoic chamber (++).
> Most of the time open-air measurements are not allowed for evident
> possible disturbances to the environmental area.
> Specialized and authority agreed body's are allowed to produce a
> certification.
> In some specific cases, the manufacturer may certify by themselves
> hiss equipment.
> Note that the test and measurement equipment's used to do the
> certification must be certified to (in hiss domain).
>=20
> I like to mention, in order to avoid confusions, that those tests are
> standard requirements for all equipment's (from dishwasher to..) and
> have nothing to do with the specific concept of a wireless alarm
> system.
>=20
> The above was only a scratch of reality but had the intent to mention
> that a design has to undergo general certification tests.
> Its wise to take in account that hidden requirement during design
> because when the certification limits are exceeded its difficult to
> resolve them latter on (additional shielding, filtering, ++).
>=20
> Paul
>=20
>