Electromagnetic compatibility

Electromagnetic compatibility (CEM) is the aptitude of an apparatus or a system electric, or electronic, to function in its electromagnetic environment in a satisfactory way, without producing itself of the intolerable disturbances electromagnetic for all that is in this environment.
A good electromagnetic compatibility describes an electromagnetic state of good neighborhood :
To limit the level of the nondesired emissions coming from the apparatus, in order not to disturb the radio reception or the other equipment.
To be sufficiently immunized against the disturbances coming from the other equipment, or more generally from the environment.
The electromagnetic and radioelectric noises are the result of all the electric currents inducing a multitude of fields and interfering signals.
The various regulations require an electromagnetic level of compatibility to respect. They thus established methods evaluation of the disturbances, as well as limits of level of disturbance not to be exceeded or support in a given environment.

Anechoic room RF used for tests CEM, emissions and immunities radiated
Magnetic compatibility.
Electromagnetic disturbance.
Electromagnetic phenomenon likely to create disorders of operation of a device, an apparatus, or a system or to affect unfavourably the living matter or inert. An electromagnetic disturbance can be a noise, a nondesired signal or a modification of the propagation medium itself.
Electromagnetic pollution.
The majority of electrical equipment and electronic generate perceptible electromagnetic fields in their environment, the whole of these fields created a true pollution which disturbs sometimes the operation of other equipment. Thus, it is interdict to use a cellphone on an aircraft because it emits an electromagnetic field to which the radioelectric systems of assistance to control are likely to be sensitive.
Electromagnetic compatibility, indicates moreover.
Techniques allowing to obtain the electronic compatibility of an apparatus or an installation with its environment.
Techniques allowing to check the reality of this compatibility.
Electromagnetic compatibilities.
Compatibility between colocalized transmitters and voluntary receivers.
Emission ⁄ Susceptibility.
Compatibility having to be assured in the two directions, one is led to define two types of phenomena :
The emissions or disturbances indicate the signals whose propagation is likely to harm the good performance of the objects or the health of the living beings located in the vicinity.
Susceptibility indicates a behavior of an apparatus, in answer to an external constraint, considered to be incompatible with a normal use. Susceptibility is also called immunity.
Phenomenology CEM: the model source ⁄ coupling ⁄ victim.
That it is of emission or susceptibility, the phenomenon does not occur that if there is, simultaneously :
A source.
A victim.
A coupling between the two.
That only one of these elements is absent and the CEM is restored.
The configuration of the model source ⁄ coupling ⁄ victim depends on the scale to which one looks at it :
A source can be broken up into another source and a coupling: for example, the radio broadcast of a microprocessor is the result of the commutation of logical cells, the metallization of the chip as well as the tracks of the case or of the printed circuit being used as antenna to transform the temporal transients of current in each individual cell into an electromagnetic field describes by a frequential coloured fog.
A victim can also undergo this type of decomposition, but its criterion of susceptibility also varies according to whether one looks at the component or the system: for example, for the same Ethernet network, one will be able to focus oneself.
On the disturbance of the logical level or diagram of the eye falsifying a bit.
On the risk that the redundancies associated with coding with the screen do not make it possible to reconstitute it.
On the acceptability or not of the reduction of band-width caused by the reissue of disturbed screens (TCP ⁄ IP).
On the intelligibility of the analogical signals reconstituted in spite of the disturbed screens.
This kind of decomposition is not indefinite: one always ends up arriving at ultimate sources. Idem for the victims. Even at this stage, one is not completely stripped.
In order to characterize the behavior of an apparatus independently of the others, the couplings are necessarily broken up into two pennies coupling: source ⁄ environment and environment ⁄ victim, therefore the standards call upon various types of environments. Residential and commercial light or industrial in the majority of the cases.
Classifications of the disturbances
Classification by conduction and radiation

Coupling by radiation and conduction
The couplings in two categories are classified :
Coupling by radiation : electric field, magnetic field, electromagnetic field.
Coupling by conduction : transmission of the signal by a conductor.
The border between the two comprises a share of arbitrary, certain standards classifying certain couplings by electric field or magnetic in the box conduction.
In addition, for the couplings by radiation, the standards make also the distinction between close fields and far fields : A source of electromagnetic disturbances often creates at the beginning either an electric field, or a magnetic field. But at a certain distance from this source, the wave observed will be a plane electromagnetic wave, combination of a field H and a field E, with the report ratio E ⁄ H = 120 π ( ≈377). This distance is of about size wavelength. Thus, for the raised frequencies, there will be always a plane wave as soon as one moves away a little the source.
The standard will be able to require a test of susceptibility to the field E, the field H or to the plane wave. The standards will require tests with the wave planes at the highest frequencies, since in the case of the raised frequencies, one will have a plane wave always in practice
Classification by frequency
f < ~ 9 kHz :
They are mainly disturbances of differential mode.
The magnetic fields and electric of the equipment of power are also to consider in certain cases.
~9 kHz < f < ~300 MHz :
Disturbances conveyed primarily in common mode, but can have a source of differential mode.
The radiation in this waveband is very often conveyed by the cables which make antenna.
One finds broad band noises in general coming from fast commutations of the converters of energy.
f > ~300 MHz :
Disturbances of common mode.
The more one goes up in frequency, the more the disturbance will be visible only according to one precise angle.
These disturbances are primarily due to the internal clocks of the equipment, the harmonics of these clocks or of the broadcasting transmitter.
Classification per duration
Permanent disturbances.
They are the disturbances coming primarily :
Of broadcasting transmitter.
Magnetic field generated by the feeders.
Deformation of the supply voltage.
In general, in the regulation, the immunity of the apparatus must be sufficient to avoid a degradation of function beyond the specification during the exposure to this type of disturbances.
Transitory disturbances
They are disturbances coming primarily :
electrostatic discharges.
Waves of the lightning.
Electric commutations in the network of energy.
Hollow of tension.
In the regulation, it is overall allowed that the susceptibility of the apparatus allows a temporary degradation of function, but with car-recovery of this function once the finished disturbance.
Classification by type of coupling
One calls coupling the process by which the energy of the disturber reaches the victim. Each time one speaks about current, tension or field, one will not forget that they are variable electric quantities in time.
Impedance coupling common
The electrical circuit of the disturber has in this case a common impedance with the electrical circuit of the victim. At the boundaries of this common impedance a tension generated by the current is passing in the disturbing circuit. As this impedance is also present in the circuit of the victim, this victim undergoes this parasitic tension. Example: two apparatuses are connected on the network 230 V: a disturber which generates parasitic tensions on the tension of the network and a victim which uses the tension of the network and which recovers at the same time this parasitic tension.
Capacitive coupling

capacitive cross talk
In this case, there exists on a disturbing circuit a tension likely to produce disturbances. There exists also a capacity between this disturbing circuit and another circuit, which will be the victim. By this capacity, disturbing electrical energy reaches the circuit victim.
Example: the phenomenon of capacitive cross talk. A conductor pertaining to the disturbing circuit is in the same cable as a conductor pertaining to the circuit victim. These two conductors being close, there exists a capacity between them, person responsible for the coupling. The coupling will be all the more high as the impedance of the circuit victim is large, because of the tension divider bridge made up of the capacity and the impedance of the victim.
Inductive coupling

inductive cross talk
In this case, there exists in the disturbing circuit a current likely to produce disturbances. Near this circuit a circuit victim is. The current of the conductor of the disturbing circuit produced around him a magnetic field. This magnetic field induces a current in the circuit victim.
Example: Inductive cross talk. The conductor of the disturbing circuit is in the same cable as the conductor of the circuit victim and armature in this last a parasitic tension. The lower the impedance of the circuit victim will be, plus this tension will induce an important disturbing energy in the circuit victim.
Coupling by electric field
This coupling is also called coupling field with wire. It is an incidental electric field which will produce a disturbance on a circuit victim. Let us notice immediately that the referred to above capacitive coupling is of comparable nature, since the capacity of coupling brings lines of field on the victim. The difference here, it is that the disturber is more distant: Instead of identifying the disturber itself, one identifies the electric field which in is resulting.
Example: the electric field of impulse resulting from a spark plug of engine reaches the antenna of a receiver car radio.
Coupling by magnetic field
This coupling is also called coupling field with loop. It is a magnetic field, resulting from a disturber, which crosses a circuit victim and thus induced in this circuit a parasitic tension. It is induction. Let us notice there too that this coupling is of comparable nature that the inductive coupling referred to above Instead of identifying the disturber itself, one identifies the magnetic field which it generated.
Example: a love at first sight near the victim. The lightning is an electrostatic discharge characterized by a current of several tens of thousands of amps and boarding time of about a microsecond. The tension induced in a loop is thus important because of important variation of the intensity of the current, but also of the speed of the rise of this current.
Coupling by electromagnetic field
Often, a disturber emits at the same time electric fields and magnetic fields, it is the whole of these two fields which reaches the victim. However, even if a disturber emits at the beginning only one electric field, the Maxwell's equations show that at a certain distance from this source, a magnetic field will also appear, to form an electromagnetic plane wave. It is the same if the disturber emits at the beginning only one magnetic field. This transformation takes place at a distance corresponding to a considerable fraction wavelength. It is thus large for the low frequencies, but short for the high frequencies. It is one of the reasons for which measurements of CEM are not the same ones for the low frequencies and the high frequencies. For the raised frequencies, there will be almost always affaire with an electromagnetic plane wave.
Classification by mode of propagation
One hears very often of the two modes of propagation: differential mode and common mode. One could have included these two definitions in the modes of couplings, but the importance of these two terms, in particular the common mode, deserves that one defines them with precision.
Propagation in differential mode

Differential mode
Are two conductors connected to an electrical appliance or electronic. It is said that a tension is applied in symmetrical or differential mode to this apparatus if the tension is presented between the two conductors. For example, the supply voltage of the sector is applied in differential mode. Or even the tension presents on a pair of telephone wire.
If one considers the cable consisted all two conductor, the algebraic sum of the currents in this cable null, since there are a current outward journey in the first conductor and a current of the same return intensity, but is opposed, in the second conductor.
To avoid the problems of CEM, it is enough that the two conductors are sufficiently close.
Propagation in common mode

Common mode
The propagation of a disturbance in common mode is regarded by the majority of the engineers in CEM as the main issue of the CEM! What justifies that one is delayed there a little.
That is to say a cable made up of several conductors, connected to an electrical appliance or electronic. Let us suppose that external electromagnetic fields induce a stray current in the whole of the conductors of this cable. This current enters the apparatus victim by this cable. Let us notice that in the differential mode, there existed in the cable a conductor for the current outward journey and a conductor for the current return. It is not the case here: the electromagnetic field induced currents in phase in all the conductors of the cable. As there is no conductor of return of this current in this cable, it is necessary to raise the question to know by which way the current of common mode will be closed again, since in theory, a current traverses a closed circuit
Since this current entered the apparatus, it necessarily will arise from the apparatus :
By other cables of the apparatus, if they exist.
By a ground conductor, if there exists.
By the capacity between the apparatus and the ground, which always exists.
This current, via these three possible ways will end up turning over to the ground. It then will circulate in the ground and will return to buckle the circuit, in theory until the other end of the cable considered. The end of the cable will be the apparatus from which the cable came, for example its feeding etc the circuit is thus buckled.
This current is known as of common mode. Its circuit can be very large :
In length, because the cable can come by far. Think of network EDF.
In width, because the cable can be high compared to the ground.
Thus the surface of this circuit can be large, it results from it :
The flow of the magnetic field crossing this circuit can be large.
The ddp between the elements of this circuit can be high.
It results from it that external disturbances can create important currents in this circuit and disturb the apparatus. Indeed, this interference current which enters the apparatus, if nothing is done, will cross the electronic chart and will disturb the electronic circuits which it comprises.
We considered until now that the apparatus was victim. Let us imagine that it is the apparatus itself which generates a disturbance in this circuit, for example by generating a current RF on its cable. This current will circulate in the circuit of common mode referred to above. As this circuit is very large, it will play the part of an antenna and will create disturbances very far. The apparatus will be an important disturber.
To reduce the effects of these disturbances of common mode, that the apparatus is victim or disturbing, the apparatus must be suitably treated with the level of the connector industry of entry, by the suitable techniques of protection CEM. For example, one will impose on the currents which enter by each conductor of the cable of going directly to the mass of the apparatus and to thus avoid passing by the functions of the chart. It is preferable also to connect the mass of the apparatus to the ground, or the plan of mass. Or, one will try to prevent these currents from entering the apparatus, while threading in the cable a ferrite core says suppressor of common mode. One can also armor the whole of the conductors of the cable and connect the shielding to the mass of the apparatus, on arrival of the cable. The current of common mode, which passes only on the surface external of the shielding, is thus derived towards the mass and does not cross any more the electronic chart.
We considered until now that the return of the current of common mode was done by the ground. In the complex systems, one often finds a plan of mass common to the various apparatuses. It is obviously then this plan which holds place of ground. One can in this case reduce the disturbances of common mode by maintaining the cables of entry more close possible of the plan of mass of the system, in order to reduce the surface of the loop of common mode.
We dealt with the problem of the common mode by considering the currents. In the technical literature, one sometimes not considers the currents, but the tensions of common mode. These tensions are present between the conductors of the cable and the ground. It is obviously a dual point of view.
One encounters problems of common mode even for the frequencies of several hundred megahertzes. One can even say that in fact the problems multiplied since the expansion of the radioelectric emissions. On these raised frequencies, one will note simply a difference with regard to the loop in common mode : As this loop is of size higher than the wavelength, one should not any more take account of the surface of the loop, but to consider quite simply that the cable which enters the apparatus is an antenna which collects the disturbing radiations. Protection in common mode of the victim will always consist in preventing these currents from entering on the electronic chart. If the apparatus is regarded as disturber, it will be prevented that the internal currents do not leave the chart, knowing that filtering will be the same one.
Electrostatic discharges
It is about the natural parasitic source, probably most widespread. The mechanism is the following :
The body of an human being is charged by tribo-electric effect.
The accumulated loads discharge brutally, when a opportunity arises: it is the electrostatic discharge.
Not only it is very unpleasant for the charge carrier, but, if the object which was used as occasion is of a fragile naturalness, it is likely not to appreciate. The possible consequences for an electronic material victim are :
Destruction of a component.
Transitory analogical phenomena.
More complex, certain methods of immunization of a material will be able to lead its users to fear or refuse to make use of it, to avoid electric shocks.
The phenomenon discharges electrostatic of human origin is modelled, in standardization, by :
A generator of impulse, model electric of the human body, consisted of a circuit capacity + resistance, in series, the majority of the standards call upon a capacitor of 150 PF discharging in a resistance from 330 Ω, this model, too coarse to describe the impulse completely, is supplemented by temporal characteristics.
A geometrical model of a human finger, being used as output electrode with the generator, accompanied by a scenario of coupling.
A level of severity, being able to be the initial charging voltage of the capacitor, or the peak value of the impulse, variable according to the degree of precautions against the electrostatic discharges which it is reasonable to wait of human which is in the vicinity.
The lightning
With the lightning, one does not leave the field of triboelectricity, one changes simply scale. A cumulonimbus, they is several cubic kilometers of a mixture of air, of, droplet steam and particle of ice, the whole brewed by currents violent one. After a few tens of minutes of this mode, the quantity of cumulated load is colossal. These loads are distributed with the small happiness in positive or negative pockets, creating potential differences amounting to megavolts. To supplement the table, the pockets located in the lowest layer create, on the ground flown over, of the zones charged by influence, opposite sign.
When the electric field is sufficiently raised, one or more pockets discharge mutually. That can occur
Maybe because, in a random way, the local radius of curvature of a pocket of load is enough tiny room to reach the field of ionization of the air to altitude considered, which starts, gradually, a kind of chain reaction.
Maybe because a conductor walks in the corner, with for effect :
To decrease the insulating distance between pockets of loads.
To introduce the equipotential ones with weak radius of curvature.
Blow, for little that the initial field is rather high, one is nearly certain to start an ionization transforming itself into blasting.
In a case as in the other, it should be remembered that the lightning is a natural process complexes, utilizing as well the laws of electrostatics, electromagnetism, thermodynamics, aerodynamics etc etc It exists relatively satisfactory models of the phenomenon, to 1,2 or 3 dimensions. And of the photographs of real blasting which show things much more complicated.
Let us return to the blasting of an airliner, phenomenon which occurs about every 2000 or 3000 hours of vol. the basic scenario, which often occurs is the following :
The aircraft puts the nose in a zone at raised field, in fact thus the any intermediary or from top to bottom nose is struck down, or from right to left, in the direction of your choice: all depends on the position of the pockets of loads at the beginning and, therefore, of the orientation of the electric field.
During tens or hundreds of milliseconds which it is necessary to drain the pockets of loads, possibly with jolts, the channel of plasma being used to run out the current of the lightning is subjected to multiple influences, the principal ones being :
The magnetic field produced by the current of the lightning tends to increase any local radius of curvature and, therefore, to destabilize, deform, even burst the channel.
The variation in temperature, which tends to center the current where the weather is hot, any physical displacement of the channel having to pay itself of a heating of the new way.
The current is thus unstable, but with an important inertia.
And the aircraft, in all that? It continues to advance, with a speed of about 100 to 250 m ⁄ S: a large airliner advances its own length in approximately 300 ms and it is thus swept by the arc which, it, remains more or less fixed, according to a process obviously not linear.
The place of the impact, the current of the lightning vaporizes a short period of aircraft, which provides an excellent electrode to benefit from the short cut that the aircraft constitutes.
As the aircraft advances, this entrance point moves away from the overall advance: the current of the lightning starts to make a turning, of which the length increases very quickly as soon as the magnetic field is exerted on him.
Blow, the field at the beginning of the turning starts to increase, sufficiently to bore a new hole.
It is like that an airframe touched by a quite high, respectful blasting of the model, is found decorated with a pretty dotted line, with a variable spacing according to the presence and the thickness of painting.
With occasional fixing a little more prolonged on things which exceed.
All this until the moment when the exit or entrance points arrive at a bottom of bag: the power of the lightning, if there still exists after all this time, ends up being replugged on itself, without being on by the aircraft, when the field caused by the voltage drop along the turning is sufficient to ionize the air at the boundaries of the turning.
Naturally, there exist multiple cases of blasting impolite fellows, which refused the model that one had provided for them.
For the rockets, it is about similar, in more vertical. More some differences :
The gases at exit of conduit of a rocket motor are much hotter than those outgoing of a turbojet, which make them easy to transform into channel of blasting.
The rockets being used to study the lightning are provided with one leaves connected to the ground, providing, while volitilizing, a natural channel with the started lightning.
Other electrostatic discharges
So electrostatic loads accumulate on an isolated object, it will be able to occur an electrostatic discharge as soon as the potential of this object reaches a certain value: there will be discharge between this object and another object of its environment. The air itself contains loads: The small loads, consisted light ions, are due to the ionization of the gas molecules by radiation UV of the sun. Larger loads are consisted by charged dust, or water droplets charged. Thus, an object which moves in the air can recover these loads, which will make assemble its electrostatic potential compared to its environment. Even a motionless but isolated object will be able to recover loads, if the air moves. For all these reasons, it often happens that an object remained insulated will be able to generate an electrostatic discharge with its immediate environment. If the object belongs to an electronic device, the discharge will be able to take place through a capacitor of insulation and to destroy this last. For this reason the antennas of the systems of telecommunications never are insulated perfectly uninterrupted and that tests CEM are also applied to the antennas of the radio operator terminals.
Some other natural sources
Transmitters: broadcasting, television, telecommunications, radars etc
The hertzian equipment, independent source of radiated electromagnetic fields, is governed by the European directive 1999 ⁄ 5 ⁄ THIS known as RTTE
If they are the subject of exemptions compared to directive CEM, in particular for the maximum level of emission, they must bring the same guarantees as the other apparatuses as regards electromagnetic compatibility.
The fundamental standard of immunity to the electromagnetic fields (CEI ⁄ IN 61000-4-3) envisages right now the possibility of tests up to 6 GHz, in order to take into account the higher frequencies of the transmitters. However, the standards produced in general limit the use of the fundamental standard up to 1 GHz or 2,7 GHz. A long-term evolution is designed to make evolve/move the fundamental standard up to 18 GHz. The modulation used usually by this standard (AM 80% 1 Khz) is however not representative of the equipment with broad band, even if the simple modulation AM is recognized like most perturbing towards the equipment.
The limits of immunity of the fields civilian and medical are given according to the current cases in a standard environment. The levels of necessary immunity are of 1 V ⁄ m (in protected environment), 3 V ⁄ m (residential), 10 V ⁄ m (industrial) and 30 V ⁄ m (exceptional). In the car fields, aeronautics, or soldier, certain specifications require levels of immunity expressed in Kv ⁄ Mr.
These levels of immunity of the equipment make it possible to function as envisaged in the presence of transmitter in the vicinity. The regulation envisages, through the standards produced, the use of a category of apparatus (electrodomestic, TV, industrialist, telephone) in a standard environment (residential, industrial). However, the levels of standard immunity do not make it possible to make sure of the immunity of an apparatus under all the conditions under which it could be exceptionally placed.
As, the limiting levels of immunity of the equipment recommended in the civil standards are lower as the limits of human exposure. Thus, it is possible that in the vicinity immediate of a transmitter whereas this one respects the regulation by all its aspects, equipment which respects to him also the regulation can be disturbed. That can pose problems for the electronics components of safety or support of life.
Transients in the networks of energy due to the exploitation of the network
In this category, the disturbance is of human origin and is related to the closing of an outer loop.
For example, it is necessary to imagine :
A basic powerplant.
A big city, for which the 5 GW represent only part of the needs.
Between the two, two more or less parallel lines high voltage, on 1.500 km.
However, 1.500 km correspond to a quarter wavelength λ ⁄ 4 of a signal with 50 Hz. For reasons of maintenance, only one of the two lines is opened with the strong current of the power station. Finally, a line outward journey and a line return are formed and are similar to a circuit tuned to λ ⁄ 2: the tension manufactured by the power station is in opposition of phase at the end of the 3.000 km of line compared to the tension coming directly from the power station. One can obtain easily 800.000 effective volts, just separated by an open switch.
With the closing of the switch, the tensions in opposition of phase are assimilable by the power station like a short-circuit.
Until a new balance is established, the 5 GW produced by the power station will be consumed entirely at the moment of closing by the dynamic short-circuit.
In the European electrical communication with a grid and entirely inter-connected, this kind of operation is carried out several times per day. However, resonance not being never exact and the nature distributed of the loads and other sources provide a damping. Despite everything, with each one of these closings of outer loop, the whole of the European network is strongly unbalanced during several seconds. The countries in end of line, play the part of reflectors particularly.
This kind of phenomenon, although attenuated as far as possible, leaves traces to the end user. It is also necessary to add to these residues all the similar phenomena assigning the various networks to increasingly low tension to the user.
Indirect effects of the lightning
When the lightning falls some share or that a flash occurs within a cloud, the current produces an important magnetic field of impulse, which comes to be coupled with all the surrounding conductors.
Commutations high tension currents
The prototype of this kind of source is the omnipresent feeding with cutting.
Low commutations currents
The majority of the modern electronic charts call upon fast logical circuits. These integrated circuits and connections which associate them are the seat of currents with faces stiff, likely to radiate electromagnetic waves on a broad spectrum. Although rather low levels, these radiations can in particular disturb the receivers radios placed in the vicinity. It is enough, to be convinced some, to place a radio operator receiver near a computer the originators of these systems must respect directives CEM concerning the radiation of the apparatuses and the led emissions which could be present on the cables of exits of these apparatuses.
The malicious ones: IEMN, electronic war, weapons ultra high frequencies
It is necessary to return this justice to the soldiers of all the countries: since Archimedes and its mirrors burning, supposed to have set fire to the Roman fleet in front of Syracuse, they liberally financed many ideas of Death ray, with variable results.
Among the multitude of serious ideas or mild nutters on the matter, there are 3 concerning particularly the CEM of them :
The electromagnetic impulse of nuclear origin (IEMN), not inevitably so nuclear that besides.
The electronic war: lures, jammers and other catch-radars or killers of conversation.
Latest fashion: electromagnetic weapons.
Electromagnetic impulse of nuclear origin (IEMN)
Since 1946, the government of the United States acquired two certainty :
The USSR was going to not yet invade the piece of Europe under its control, at the time of a surprised attack being able to intervene from one hour to another.
Taking into account the number of soldiers on both sides, the only weapon making it possible to guarantee a Soviet defeat was the atomic bomb.
The American army thus launched out in a vast program of tests of nuclear weapons. New Mexico, where the first bombs exploded, comprising a too high density of inhabitants to continue of it the irradiation and Japan having become an ally, these tests took place on the atoll of Bikini. With the short-nap cloth of the ground, under water, in the air, bombs of aircraft, artillery shell or mine, including two successive shootings in the upper atmosphere.
After each one of them, it broke down electric in Hawaii there. Breakdown caused by a giant electromagnetic impulse, which, coupled with the electric lines, started all the circuit breakers. And the American military officials seized the potential of a giant electromagnetic impulse as a weapon.
An atomic bomb emits ionizing radii. And the ionizing radii, that ionizes what there is around, to start with the air. It is as that which appears a fireball, pulp of electrons and cores of nitrogen, oxygen and other atoms present on the spot.
Because of the temperature and pressure of radiation, this ball undergoes a fast expansion: electric charges which move, here is a good base to create an electromagnetic impulse, not.
Not. that does not go. The electrons and the cores make approximately the same way, therefore their respective effects are compensated.
Yes, but all that occurs in the terrestrial magnetic field. Blow, while moving, the electrons will leave in skew in a direction and the positive ions in the other and there, one has it our impulse, not.
Not. that still does not go. As the ball extends in all the directions, the imbalance of north will be compensated by that of the south, that the top by that of bottom, that of the east by that of the west. One is recovered one dipole moment. By what to extinguish the tele one to 1000 km.
But to the fact, that occurred during shootings to high-altitude. If the bomb explodes rather high, there will be no more fireball top, considering there is not enough air to ionize. And unbalances it of the low part of the ball, caused by the separation of the loads + and - by the terrestrial field, will be compensated any more per nothing.
Calculation of the ideal place where to explode the bomb to sprinkle a whole continent, calculation of shielding, of filter, measures of behavior of the components, hardened communications : here are goodwills which will have nourished its world, during 40 years At the great time of the cold war, certain American strategists regarded as asset that all the missiles embarked on submarine would be used to manufacture IEMN with continuous jet, only the missiles on the ground being enough precise to only destroy the silos of revenge in the American plains, here: the missiles on the ground have about thirty minutes of voyage to make, whereas a submarine placed well can begin the fireworks 5 minutes after having declared the war, they were to thus be used as aperitif, to prevent the victim from reacting. It should be said that, even if one carefully avoided informing the backers of them too much, the vulnerability of the electrical communication became less and less obvious: with increasingly large mesh networks, the IEMN was seen caught up with, in terms of worse forced, by the closing of outer loop, at least on the energy level. Since, the tendency is with the thin cows: with the end of the cold war, the new potential agressors do not have enough bombs to waste some to make parasites. The threat is thus less and less credible.
A last word on this kind of gadget : there exists another means of breaking symmetry, it is to explode the bomb with the short-nap cloth of the ground. that functions, but with an operating range more limited. One realized besides that the atomic side was not essential: a bomb FAE is able to manufacture an electromagnetic impulse.
Parasitic rectification
A signal HF from the point of view of the circuit which receives it perhaps modulated demodulated by a circuit victim. If it is modulated in amplitude or in certain cases in frequency, at the time of waveband of resonance of the victim narrower than the width of modulation of the signal source, the demodulated signal will be injected into the circuit. There will be demodulation of amplitude if the circuit is nonlinear. Any electronic circuit containing of the semiconductors is nonlinear as soon as a certain level of signal is reached. The low amplifiers level, which saturate more quickly, will be more sensitive to these phenomena of demodulation of amplitude. The audio entry low level of the amplifiers must thus be the subject of an special attention. If the signal HF is not modulated, the level even signal HF rectified by a circuit victim can generate a continuous tension in the circuit. What modifies the point of polarization of the components, involving blockings or saturations.
Any signal with strong factor of form, modulating or not carrying, can cause a change of state of a logical circuit. If this circuit takes part in a sequential automat such as a computer, the internal state is likely to be modified about it. Later operation becomes aberrant.
It is an extremely insidious alternative of the preceding case. It should be remembered that the concept of circuit logical is purely artificial. It is acted in fact analogical of circuits to non-linear transmittance. Following a disturbance, it happens that an exit finds with the state ½ some share between 0 and 1 during a time which can amount to milliseconds.
Law of helping Moore, this phenomenon, highlighted with first logical circuits CMOS, now presents a risk for all technologies of integrated circuit calling upon the insulation by junction in reverse. During the manufacture of an integrated circuit, one creates, with the passage, of multiple structures PNPN having a sufficient gain to constitute a thyristor. It is enough that a phenomenon of impulse starts one of these thyristors so that this last shorts-circuit the feeding.
From there, several things can occur :
That is to say the gain is a little right and the thyristor car-is defused: that resembles the metastability.
Either one remains in this state to cut of the current.
Either one roasts a fuse, some share in metallization and the circuit is destroyed.
Biological effects
Electromagnetic compatibility relates to, by definition, only the effects towards the equipment and not towards the people or other entities biological.
However, several electromagnetic phenomena are to be considered :
Heating effects: An electrification by contact or a sufficiently powerful electromagnetic field can heat the substances which are exposed there. For the heating effects of the electromagnetic fields, in the electric regulation of safety, this subject is covered within the framework of the limitation of the human exposure to the electromagnetic fields. This regulation makes it possible to limit the excessive heating of biological fabrics, without however of undeniable proof that this one is enough to avoid any biological effect on the long run.
Nonthermal effects: The existence even of these effects is prone to polemic. These effects are difficult to prove because, on the one hand, it would relate to a minority category of population having a potential of electromagnetic over-sensitiveness and on the other hand completely unquantifiable because the phenomenon source of these effects is not identified.
Obtaining the CEM
To obtain or improve compatibility, one can exploit the 3 terms of the triad source ⁄ coupling ⁄ victim :
To decrease the level of emission of the sources, for example, in the field of the energy transformation :
A converter with resonance will be, if it well is conceived and well established, much less slobbery than a converter with hard commutations.
The replacement of a traditional rectifier diodes + condensing by a rectifier with PFC will avoid largest of the injection of harmonic current in the network energy.
One can also quote the replacement, by EDF, of the spark-gaps with horns serving of clipping on his lines 20 Kv by varistors with zinc oxide, for the greatest happiness of the merchants of telecom.
To decrease by level of vulnerability of the victims.
The introduction of the spreading out of spectrum into the radio communications decreased much the capacity of harmful effect of the parasiteurs with narrow band.
But if, as it is too often the case, all the errors of design are already fixed before worrying about CEM, one cannot act any more but on the couplings.
That will often consist in treating the environment of the electronic charts of the apparatus in question, whether it is victim or pollutant. There exist 6 methods making it possible to separate from the victims of their torturers:
Suppression of the common mode.
Frequential filtering.
Temporal filtering.
The chopping.
The gate of noise.
The electromagnetic shielding consists in dividing space into separate, unquestionable fields electromagnetic clean and the other dirty ones, without any communication between them. In practice, an electronic chart will be placed in a metal case which will protect it from the external radiations.
A shielding is very effective in theory, as soon as the frequencies blamed exceed the megahertz. In practice, it is differently, because an electronic chart is generally in relation to outside by electric cables, would be this only the feeding. It is noted whereas the effectiveness of the shielding can be reduced with nothing if the currents of common mode are not blocked on the level of the entry of the cables.
Removal of the signals in common mode
See the paragraph common mode for the definition. Protection against the signals of common mode consists, for an apparatus victim, to prevent the currents induced on the cables, to penetrate in the electronic chart and to disturb the functions which are there. For the disturbing apparatuses, this protection consists in preventing the stray currents leaving the chart and from going to circulate on the external cables. The protection of the common mode thus aims the same goals that a shielding and often makes this last effective. Indeed, it is not used for nothing to armor an apparatus, if the disturbances pass by connections which enter the shielding.
Here some rules of protection against the signals of common mode, valid as much for the disturbers that for the victims.
If the apparatus concerned has a metal case and if the chart has a layer of mass, protection will be easier to obtain: One will have, if it is possible, to armor the cables which enter on the chart, by connecting this conductor of shielding to the mass of the chart and the metal case at the place of the entry in the case, i.e. as of the arrival on the connector industry.
But it is not always possible to armor the cable of entry. Then, it will be necessary to carry out a filtering of the currents of common mode. Of course, one cannot filter, block or uncouple the signals from common mode that if the useful signals transmitted by the conductor are of lower frequency. If the useful signals are in the same band as the signals of common mode, only the shielding of the cable will be able to solve the problem. To filter the common mode, one will treat each conductor of the cable so that the currents of high frequencies arriving by the conductor are blocked or derived towards the mass from the chart and the metal case, by the shortest possible way. The way of the current of common mode resulting from outside is the following: It enters by the conductors of the cable, it passes to the mass of the chart by the capacitor of decoupling, then borrows connection between the mass of the chart and the case, then it circulates then on the interior surface of the case, in order to arise from the case by the hole of the cable. Indeed, it should not be forgotten that the current circulates only on the surface of metal and the wall of the case will never cross! Thus, if decoupling is carried out on the chart, it will be necessary to reduce to the maximum the way of the current of common mode inside the case, to avoid the radiation inside the case.
Decoupling will generally consist of an impedance series and a capacity towards the mass. If decoupling towards the mass of certain conductors is impossible, the impedance in series with these conductors will have to be sufficiently large out of HF.
If the apparatus does not have a metal case, protection will be more difficult to obtain: One will place filterings on each conductor, and one will gather all the arrivals of cable on the same side of the chart: indeed, the current of common mode, which goes from one connector to the other while passing in the mass of the chart, will take the shortest possible path thus and will not cross all the chart. Even with only one arrival of cable, the power of common mode will tend to be on by the capacity between the components of the chart and the environment, by capacitive coupling. By from the beginning deriving towards the mass from the chart the current from common mode, one reduces the busy currents by the other components. If the apparatus is already designed, a makeshift will consist in threading in the cable a ferrite of suppression of common mode, of sufficient impedance.
If the chart of the apparatus does not have a plan of mass, protection will be very difficult to obtain. One will have to impose only one arrival of cable, in order to minimize the currents of common mode through the chart.
The filtering of the frequencies
One separates the field from the useful frequencies of that of the polluted frequencies, in the condition that they are not the same ones, of course, because all the signals are not filterable. One saw for example in the paragraph suppression of the common mode which one could uncouple by a capacitor certain connections. They are generally connections for signals of low frequencies or even for the continuous one. This decoupling is not anything else that a filtering passes low. Filtering could be implemented for the symmetrical mode or the common mode. Alas, modern technologies implement increasingly fast useful signals and one often runs up against the fact that the useful signals and the disturbing signals occupy of the common wavebands.
Temporal filtering
If the signal pollutant is not present permanently, it is enough to put the victim at the shelter during the bad weather :
It is the principle of the radar monostatic with impulse : a transmitter and a receiver divide the same antenna, but the transmitter makes use only very little of it.
In a synchronous sequential automat, with each blow of clock, million rockers commutates simultaneously, putting the feeding at knees, nevertheless, the last millivolts are enough so that, when the light returns, these rockers are in the desired state. Then, the circuitery of combinatory logic becomes again functional for mitonner the good states in entry of rockers, in time for the blow of clock according to. Whereas in the event of multiplicity of clock, the risk of logical states Mulderiens would be permanent.
The chopping
In a general way, one speaks about chopping in tension. When the disturbing signal is of great amplitude, the equipment victim is likely to suffer irreversible damage, the chopping consists in limiting the amplitude of the disturbing signal in order to protect the electronics components. One finds for this purpose of the components known as limitings device that one places in parallel on connections. One admits in general that the functionality of the apparatus is stopped at the time of the disturbance, the component of chopping having before a a whole function of survival. Indeed, it is not possible to discriminate the signal useful and the disturber at the time of the chopping.
Several types of components will be used, according to the following criteria :
Low capacity.
Very high absorbable energy.
Response time runs.
Automatic rearmament etc
In a general way, the components used are nonlinear components: diodes, thyristor, nonlinear resistance, spark-gaps, etc
The gate of noise
It is typically a question of protecting an analogical signal while counting on the effect of masking :
The squelch of the radio operator receivers, which consists in cutting the audio when the radio signal is too weak to be usable.
The Dolby systems or similar, consist, approximately, in a filtering of acute if the signal is weak.
Directive CEM.
At the time of the study of the CEM of a new product, it is essential to start by knowing the environment in which this product will be placed. Directive CEM is clear in these requirements. The product will have neither to disturb, nor to be disturbed by the environment in which it is supposed being located.
According to the directive the respect of the harmonized standards shows the respect of the essential requirements. But a contrario :
Many standards produced, however always appearing like normalize harmonized, did not evolve/move since more than ten years :
The electromagnetic environment on the other hand saw appearing new radio operator disturbers using of the frequencies higher than before.
Same technologies of certain product ranges underwent such an evolution, as the application of its dedicated standard is not adequate any more.
The environment in which the product will be placed is perhaps not that which was taken into account at the time of the writing of the standard.
In these cases, the application of the harmonized standard is not satisfactory for the respect of the essential requirements of the directive. According to article 6 of the directive, it is normally expected that information went back and treated to the European level. In the facts, this procedure is applied little.
Two possibilities are thus offered :
To apply the standard harmonized in the state. This possibility brings :
A risk which the product disturbs or is disturbed in the user
A risk that during a control of market, this one is interdict with the sale by non-observance of the essential requirements of the directive.
To apply a dedicated test routine. In this case, the validation of this program by a notified organization is recommended, but not obligatory. This one is in general with the current of the draft standards in progress. This possibility brings :
An insurance which the product will not disturb and will not be disturbed in the user
That the future evolution of the standard produced could already probably be taken into account. That avoids for the products at long life of life the obligation to pass by again of the tests during the change of version of standard.
Approaches of checking of the CEM
There exist two principal approaches :
The digital simulation : one creates a model of the system to be validated, as well as a model of the electromagnetic environment and one applies an algorithm defining the couplings.
Simulation analogical, still called tests CEM :
One places a specimen of the system to be validated in an electromagnetic environment of reference and one carries out measurements, the whole being usually defined in the regulation.
Whatever the approach, it is necessary to find an optimum between contradictory requirements :
The representativeness :
The selected environment are they representative of reality.
The material tested is it representative of the series.
The model does not haggle it over futile details by leaving side the really fundamental sizes.
Taking into account thickness of metal, but not of the tolerance of the slits between components to the risk to reproduce an antenna patch.
Caps modelled with the mass whereas they are it only by one telegraphic and thus inductive connection.
Omission of the connecting cables.
Reproducibility :
Two successive tests of the same specimen will give the same result.
Two successive specimens will give the same result.
Two tests in different laboratories will give the same result.
Ethics :
In case of doubt, one makes the decision of the simplest way towards the conformity of frontage to reduce the costs, where by technical insurance.
The user, will be it satisfies of my product if as soon as its telephone sounds my product dies out.
Techniques of the tests
One distinguishes two families from techniques :
Techniques known as of emission.
Techniques known as of susceptibility or immunity
Techniques treating of the emissions
Any electrical equipment or electronics, apart from its basic operation, manufactures without our knowledge of the alternative courses or impulse whose frequency spectrum can be very wide. These currents circulate in the various cables or printed circuits of the apparatus and thus when these conductors are, from their length, of more or less good antennas, there is electromagnetic emission of field.
The emissions are measured either in a led way, or in a way radiated with the apparatus under test in the most disturbing operating process.
Within the framework of the led emissions, the apparatus under test is in general placed in a Faraday screen room to isolate itself from the external environment. The apparatus under test is then connected to a network of stabilization of impedance. This one has several functions: to remove the component of energy, to standardize the impedance of a line to improve the reproducibility of the test and to connect the receiver of measurement or the analyzer of spectrum to allow measurement.
Within the framework of the radiated emissions, the apparatus under test is commonly placed on the revolving plate of either on a site of measurement in free space, or in an anechoic semi Faraday screen room. Measurement is carried out with the assistance of antennas connected to a receiver using cords. It is of use that the whole of this measuring equipment is calibrated. The protocol of test for marking THIS or FCC envisages a research of the most unfavourable position of the apparatus under test.
By modifying the design of the apparatus, one can reduce considerably the emitted level. However, a bad design from a point of view CEM can require profound changes, including in terms of routing. It is essential that problems CEM are taken into account at the beginning of the project of design.
The acceptable levels are in general standardized. Thus, electrical equipment of civil aircrafts is treated by standard RTCA ⁄ DO160E, the equipment general public Europeans is treated by the European standards and is the subject of marking EC.
Techniques treating of susceptibilities
One calls level of susceptibility of an apparatus the level of disturbance to which the apparatus presents a dysfunction.
One calls level of immunity the level to which the apparatus was subjected during the tests and for which it must function normally.
One calls level of aptitude the level of the parameters observed on the product considered as normal for a good performance of the product.
General information
Certain apparatuses used in very polluted environment have a level of immunity much more raised, for example those used under the cap of the cars.
There exist techniques to modify the design of the apparatus so that it is in conformity with the standard.
As one can imagine it, the cohabitation of many apparatuses on an aircraft or a car, implies that all this equipment is not integrated into the vehicle without severe tests being carried out.
The CEM will determine: differences between cables, the composition of the cables, filters to be installed on the equipment, the mechanical structure surrounding the equipment.
The tests envisaged by the standards make it possible to check that the level of immunity is respected but if the test is in conformity, they do not make it possible to know the level of susceptibility of the apparatus.
Criteria of aptitudes
For each type of test, it is defined if the equipment :
Must not have loss of function beyond its level of aptitude during the test.
Can have a degradation or loss of function during the test, but must find its level of aptitude without intervention of the user.
Can have a degradation or loss of function during the test, but must find its level of aptitude with intervention of the user.
Standard tests
Tests of immunity to the radiated electromagnetic fields
The other electronics components and the intentional transmitters produce electromagnetic fields. The equipment under test must function normally when it is subjected to these electromagnetic fields.
The apparatus under test configured in its most likely operating process is placed in an anechoic room. In this cage is placed a transmitting antenna, connected to an amplifier of power, itself supplied with a generator of signal radio frequency. The whole of the necessary spectrum is then swept in frequency with the level of field and the modulation necessary.
Crushing the majority of the electronic devices currently put on the market European general public has a level of immunity to the radiated electromagnetic fields of 3 V ⁄ m for the frequencies of 80 MHz with 2,7 GHz.
The level of immunity of 10 V ⁄ m is necessary for the apparatuses intended to be used in industrial environment and the electro-medical apparatuses of maintenance of the life.
Tests of immunity to the led disturbances
Several phenomena are tested :
Induced immunity with the disturbances frequencies radioelectric: complement of the test of immunity to the electromagnetic field, but in a lower waveband.
Immunity with the fast electric transients in salvos: immunity with the fast disturbances caused by the commutation of small relay, thermostats.
Immunity with the waves of the lightning: immunity with the indirect impacts of the lightning, or the disturbances due to electric commutations of strong power.
Immunity with the hollows of tension: immunity with the disturbances caused by the cuts of tension, or them falls of tension following calls of loads on the network.
Immunity with the transients vehicles: immunity with the variations of tension caused by the calls of current of the systems of the vehicle.
In general, the protocol of test consists in connecting to a generator of disturbance dedicated, via a network of coupling ⁄ decoupling, with the equipment under test.
Tests of immunity to the electrostatic discharges.
Tests of immunity to the magnetic fields: those can be are impulse or at the frequency of the feeder system.
Materials industrialist or general public
Directive CEM.
All the products comprising of electronics are concerned with the obligations of the directives as regards CEM, the materials put on the European market must receive a marking EC, attesting conformity with the requirements rising from all the applicable European directives, of which directive CEM.
From the point of view of directive CEM, the fixed installations, not subjected to marking EC, must nevertheless bring the same guarantees as those which are subjected there.
Moreover, there exist other markings :
German initials VDE, although officially obsolete, preserve a certain prestige on its market.
Auto industry developed its own marking.
American marking FCC is the mutual recognition object.
Materials aerospace or military
The materials assembled on aircraft are the subject of certifications recognized on a world level (FAR ⁄ GRAVEL BANK), as well as particular requirements of the airframe manufacturers, checked under the control of the latter. Certification replaces marking EC. On the other hand, the aeronautical material remaining on the ground is marked EC like the ordinary industrial material which it is.
Particular requirements also for the space engines and the military material. If the statute of the first is clear), the exemption of the seconds comes from one of the clauses of the Treaty of Rome, authorizing a government not to apply a Community decision to the military material. In France, this decision, bearing on only the directing model old CEM is materialized by an interdepartmental circular, which does not have, seems it, ever notified at the commission of Brussels.

European Directive
Directive CEM

The European directive 2004 ⁄ 108 ⁄ THIS relates to electromagnetic compatibility (CEM). This one repeals the directive 89 ⁄ 336 ⁄ the EEC. The whole of the products electric or electronic entering the applicability of the directive and available on the European market must, since July 2007, being obligatorily in conformity with this new directive.
A guide of application is published by the European Union for a good application of the directive
Scope of application
Directive CEM applies to very produced electric or electronic likely to be able to disturb the electromagnetic environment, or to be disturbed by this one.
The following equipment is excluded from the field of application of the directive :
The equipment radio hams nonavailable in the trade.
Terminals of telecommunication or radio. Those are subjected to the directive 1999 ⁄ 5 ⁄ EC (R&TTE) which integrates the requirements as regards electromagnetic compatibility.
The électromédicaux equipment. Those are subjected to the directives 93 ⁄ 42 ⁄ the EEC and 90 ⁄ 385 ⁄ the EEC which integrate the requirements as regards electromagnetic compatibility.
The equipment aeronautics and car which answer a specific regulation.
Requirements as regards protection
The equipment should not disturb with in addition to measurement their electromagnetic environment.
The equipment should not be disturbed with in addition to measurement by the electromagnetic environment in which they are located.
Requirements specific to the fixed installations
The fixed installations must be realized in the code of practice as regards CEM in order to respect the requirements as regards protection.
The fitter must respect the provisions envisaged as regards CEM by the manufacturer of the component installed.
The essential requirements of directive CEM do not have concept related to safety.
It is directing low tension (2006 ⁄ 95 ⁄ EC) which integrates the concepts of safety. This directive can require, through its associated regulation, of the tests of CEM reinforced on the safety equipments. It is as through this directive low tension as the levels of human exposure to the electromagnetic fields are limited.
Associated regulation
It should be noted that the European regulation associated with the CEM comes mainly from 2 sources :
International Electrotechnique committee (CEI), which publishes standards CEI 61000-x-x, in general adopted the following year in European standard IN 61000-x-x.
Special international committee of the Radioelectric Disturbances (CISPR), which publishes CISPRxx-x standards, in general adopted the following year in European standard IN 550xx-x.
Often 2 standards apply to a product :
A standard relating to the emission of the equipment.
A standard relating to the immunity of the equipment.
Sometimes the standards do not integrate INTO 61000-3-2 and 61000-3-3 which must however be applied.
Normalizes harmonized
The harmonized standards are the standards of reference published by the official journal of the European Union. Those are generic standards produced or standards. The respect of a harmonized standard ensures a presumption of conformity directive CEM.
Normalizes produces
The standard produced is a standard, harmonized or not, which will apply to a range of specific product, in a specific environment.
This standard produced will define for a type of equipment, placed in a standard environment :
The particular operating processes in which the equipment will have to function during the tests.
For the tests of immunity, the criteria of aptitudes of the product according to the type of test.
The list of the tests which the equipment will have to undergo, by applying in the majority of the cases a fundamental standard.
The limiting levels with which the equipment will have to be in conformity.
The most common standards produced are (often to supplement by the standards INTO 61000-3-2 and 61000-3-3) :
For the apparatuses of data processing (residential medium): IN 55022, 55024.
For the apparatuses electrodomestic: IN 55014-1, IN 55014-2.
For the lighting equipments (residential medium): IN 55015, 61547.
Normalizes generic
When no standard produced exists for a range of equipment, one can apply the generic standards (which are harmonized).
The generic standard will define for a standard environment :
Generic modes of operation in which equipment will have to function during the tests.
For the tests of immunity, the criteria of aptitudes of the product according to the type of test.
The list of the tests which the equipment will have to undergo, by applying a fundamental standard.
The limiting levels with which the equipment will have to be in conformity.
The generic standards are :
IN 61000-6-1: generic immunity for the residential environment normalizes.
IN 61000-6-2: generic immunity for the industrial environment normalizes.
IN 61000-6-3: generic emission for the residential environment normalizes.
IN 61000-6-4: generic emission for the industrial environment normalizes.
Fundamental standard
The fundamental standard defines the whole of the testing method.
A fundamental standard will describe :
Essential characteristics of the system of measurement.
Often, of the typical levels of test, but it definite step the level to be applied to a product.
The assembly of test.
Procedure of test.
The evaluation of the test results.
Data to be written in the report ratio of test.
Process of evaluation
The directive requires, whatever the procedure of evaluation applied, the drafting of a technical documentation relating to the CEM preserved by the manufacturer 10 years after the last manufacture of this equipment. This technical documentation is not intended to be provided to the user, but must be at disposal of the authorities in the event of request of those.
For a good management of the CEM, several stages are to be considered during the creation of the new equipment. Technical documentation must reflect the reflections which were made when designing point of view of CEM. It is thus useful that technical documentation is written throughout the design of the product.
A product having undergone a modification compared to a first production must be easily identifiable and brought closer with this technical documentation. The impact of the modification on the electromagnetic compatibility and the respect of the essential requirements must be evaluated and described in documentation.
Identification of the apparatus
In general, it is about the model of the equipment. This name or number of model must be identical between the technical documentation and the maker badge of the product.
General description of the apparatus
A complete description of the apparatus should contain :
Functions filled by the apparatus.
Tolerances for a good performance of these functions.
The whole of the diagrammatic ones.
Nomenclature of the components.
Materials used for the shielding.
Frequencies of the clocks and buses.
The list of the access of the equipment.
One or more photographs of the equipment as a whole and the electronic charts.
Standard environment in which the apparatus is intended.
The note user, containing the relative tendencies with the CEM which the user will have to respect.
Of course, the contents vary according to the complexity of the apparatus. The guide of application of the directive indicates that for simple equipment, a line of description can be enough.
Evidence of conformity
If the equipment were evaluated in accordance with a harmonized standard, the references gone back to those must appear in the technical dossier. The results obtained following the evaluation in accordance with these standards must be integrated into the technical dossier.
If the equipment were not evaluated in accordance with a harmonized standard, a complete description of the process applied to evaluate conformity compared to the essential requirements of the directive must be described in the technical dossier. All the documents having been used for this evaluation must be integrated into technical documentation.
If a notified organization were consulted, the opinion of the notified organization will have to be integrated into the technical dossier.
Internal process
The manufacturer must evaluate the electromagnetic compatibility of his apparatus in all the relevant operating processes, for the electromagnetic environment in which the apparatus will be intended to be placed.
For that, the manufacturer must constitute a technical documentation.
A declaration of conformity IT must also be written by the manufacturer.
Technical documentation and the declaration IT of conformity must remain at disposal of the authorities 10 years after the last production of its product by the manufacturer, his representative in the European Community, or failing this, the importer.
As, the manufacturer must make sure as the products manufactured correspond to written technical documentation.
Process by qualified opinion of notified organization
The application of appendix III is not obligatory. It is up to each manufacturer to call or not upon a notified organization with directive CEM. A notified organization is an independent office whose its trade is to evaluate the technical dossiers compared to the essential requirements of the directive. Often, the notified organization is also a test laboratory.
The process of appendix II must always be applied in its entirety.
In complement, the manufacturer asks for the opinion of the organization notified of his choice, on whole or part of the essential requirements of the directive. To obtain this opinion, the manufacturer submits the technical dossier to the notified organization.
Once obtained, the manufacturer adds the qualified opinion of the organization notified to his documentation with technical documentation.
This procedure makes it possible to obtain the opinion of a third party recognized like a reference by the authorities.
Declaration IT of conformity
A declaration IT of conformity must comprise :
coordinates of the manufacturer.
coordinates of its representative in the European Union.
complete identification of the product.
a mention with the directive.
the list of the harmonized and dated standards applied, or failing this a reference to the program of evaluation applied.
additional information.
If it is necessary, the reference of the qualified opinion of notified organization.
The place or technical documentation is preserved.
The name, the date and the signature of the representative in the European Union.
A copy of this declaration IT of conformity must be delivered with the apparatus. Examples of declaration of conformity are given in the guide of application of the directive.
Marking "EC", appearing in appendix 5 of the directive, must appear on the product. The logo THIS indicates that the apparatus is in conformity with the requirements of the whole of the directives applicable to this product.
Also, other markings must be present on the product or documentation if they are imposed by the standard applied. Such as for example :
The mention "Apparatus of Class", required, for example, by the standards INTO 55011 and 55022 for the industrial plants not respecting the limits of emission of the residential environment.
The logo of warning "ESD" near the accesses sensitive to the electrostatic discharges, as recommended for example by INTO 61326.

American Directive
Federal Communications Commission

Federal Communications Commission or FCC is an agency independent of the government of the United States created by the American Congress in 1934. It is charged to control telecommunications, the standards of electromagnetic as well as the contents of the radio programs, televised compatibility and the Internet. The majority of its police chiefs are named by the president of the United States.
When it is possible, the OSHA promulgates national consensual standards or federal standards established in security standards. The obligatory provisions of the standards, incorporated by reference, have the same force and the same effects as the standards listed in the part 1910. For example, consensual standard national NFPA 70 is listed as reference document in the appendix has S-Electric under-part of part 1910 of 29 CFR. NFPA 70 is an optional standard which was worked out by the National Fire Protection Association (NFPA). NFPA 70 is also known under the name National Electric Code (NEC). By incorporation, all the obligatory requirements of the NEC are obligatory according to the OSHA.
With an aim of simplifying, for the manufacturers, certification in the USA and apart from the USA, the FCC indicated Telecommunications Bodies Certifications (TCB). A TCB is authorized to check the applications and to establish homologations on behalf of the FCC.
FCC normalizes.
FCC PART 22,24 & 27 for apparatuses GSM ⁄ WCDMA.
FCC PART 15.247 for Bluetooth apparatuses and WLAN (2,4 GHz).
FCC PART 15.407 for WLAN 802.11a (5GHz).
FCC PART 15.245 (902-928 MHz band, bands ISM).
FCC PART 15.225 for RFID (13.56 MHz).
FCC PART 25 for apparatuses satellite communication.
FCC PART 90 for private mobile devices.
FCC PART 95 for personal radio operator apparatuses.
The least constraining procedure for a manufacturer or an importer is identified under the term of "Checking".
The manufacturer or the importer tests his product according to the FCC Leaves 15 with his own means or in a laboratory third-part. The tests must of course be realized in the code of practice, in fact in site free space but no quality standard (as the Cofrac accreditation) is required on the level of the laboratory.
The manufacturer or the importer is responsible for the interpretation of the results. If it judge are equipment in conformity, it must affix on its equipment the label corresponding to the step of "Checking" and must formalize its file by putting it at the electronic format to be able to present it in the event of control.
For products with the disturbing capacity more proven (PC, terminals of telecommunication, etc), the necessary procedure is entitled "Declaration Conformity off" (Doc.).
It requires that the laboratory carrying out the tests is accredited for the FCC Leaves 15 (to be identified as CAB - Conformity Assessment Body in the Agreements of Mutual Recognition with the United States makes it possible to attest of its accreditation).
If the equipment is judged conforms, a specific marking must be reproduced on the product and a sentence specific to this procedure must appear in documentation accompanying the product. As for the procedure of "Checking", the report/ratio of tests must arise in a precise electronic format (pdf) and must be only presented in the event of control.
It should be noted that a product only made up of sub-assembly already in conformity with the requirements of the FCC can be regarded as in conformity without requiring to pass in tests. The marking of the product is similar to the precedent except that the sentence "Assembled From Tested Components (Complete System Not Tested)" replaces the sentence "Tested To Comply With FCC Standards".
The last procedure is entitled "Certification", it can be selected for all the equipment returning within the framework of the "Declaration off Conformity" but is obligatory for the receivers broad band and the transmitters.
The broad band receiver and the transmitters not subjected to license enters within the framework of standard FCC Leaves 15, the other transmitters must answer criteria which theirs are specific through the standards which are to them applicable FCC Leaves xx.
The step of "Certification" requires that a laboratory FCC listed, like Emitech, carries out the necessary tests.
The file accompanying the realization by the tests must be presented under an electronic format (pdf) and must be subjected for approval with the FCC. In the event of acceptance of the file by the FCC, "Grantee Code" is delivered which will be used as a basis for FCC ID having to be reproduced on the equipment.
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