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Abstract: Narrates the EMC definition, EMC in the monolithic integrated circuit application system’s test method, the EMC new component new material application as well as the trouble shooting technology. So long as is engaged in the electronic products the research and development, the production or the supply, must carry on the EMC electromagnetic compatibility the examination work.
Key word: EMC tests EMC the trouble shooting EMC new component application monolithic integrated circuit Introduction So-called EMC is: The equipment or the system in its electromagnetic environment can the normal work, and any thing constitution cannot withstand to this environment in electromagnetism harassment ability. EMC test including two big aspect contents: Carries on the test to the outside transmission’s electromagnetism harassment intensity, with the aim of confirming whether to meet the related standing operating procedure limit value requirement; Carries on the sensitivity test to it under the stipulation electromagnetism harassment intensity’s electromagnetic environment condition, with the aim of confirming whether to meet the related standing operating procedure interference rejection requirement. Regarding the engineers and technicians who is engaged in the monolithic integrated circuit application system design, masters certain EMC test technology is very essential. EMC is the electromagnetic compatibility (Electro-Magnetic Compatibility) abbreviation, it including electromagnetic interference (EMI) and electromagnetism sensitivity (EMS) two parts. Because electric appliance product in use time has the electromagnetic interference to other electric appliances, or receives other electric appliance’s electromagnetic interference, it not only relates the product work the reliability and the security, but also possibly interferes with the other electric appliance’s normal work, even causes the safety hazard. 1 monolithic integrated circuit system EMC test (1) testing environment In order to guarantee that the test result accurate and the reliability, the electromagnetic compatibility survey has the high request to the testing environment, surveys the location to have the outdoor open location, the screened room or the anechoic chamber and so on. (2) test facility The electromagnetic compatibility measurement equipment divides into two kinds: One kind is the electromagnetic interference measurement equipment, the equipment joins the suitable sensor, may carry on the electromagnetic interference the survey; Another kind is in the electromagnetism sensitivity survey, the equipment simulation different noise source, through the suitable coupling/decoupling network, the sensor or the antenna, exerts in each kind is measured the equipment, serves as the sensitivity or does the bending deflection survey. (3) measuring technique Electromagnetic compatibility test basis standard difference, many measuring technique, but induces may divide into 4 kinds; The conducted emission test, the radiated emission test, the conduction sensitivity (interference rejection) tests and the radiosensitivity (interference rejection) tests. (4) tests the diagnosis step Figure 1 has given an equipment or system’s electromagnetic interference launch and the fault analysis step. Carries on according to this step, may enhance the test diagnosis the efficiency. (5) tests the preparation ①Testing field condition: EMC tests the laboratory for the electric wave half darkroom and the screened room. The former uses in the radiated emission and radiates the sensitive test, the latter uses in the conducted emission and conducts the sensitivity test. ②Ambient level request: The conduction and the radiation electromagnetic environment level is best is lower than the standing operating procedure far the limit value, generally causes the ambient level to be lower than limit value 6dB at least. ③Experimental table. ④The measurement equipment and is measured equipment’s isolation. ⑤Sensitivity criterion: Generally by is measured the side to provide, and the truth surveillance and the distinction, survey and the observation way determined the performance reduces degree. ⑥Is measured equipment’s laying aside: For the guarantee experiment’s duplication, to was measured that equipment’s laying aside way usually has the specific stipulation. Conducted emission test, radiation transmission test, conduction interference rejection test, radiation interference rejection test. (7) commonly used measuring instrument The electromagnetic interference (EMI) and the electromagnetism sensitivity (EMS) tests, needs to use to many electronic instrumentations, like spectrum analyzer, electromagnetic field disturbance measuring instrument, supply oscillator, function amplifier, oscilloscope and so on. Because the EMC test frequency is very wide (20Hz~40GHz), the scope to be very big (μV level to the kW level), the pattern many (FM, AM and so on), the posture many (keep flat, to put and so on slanting), therefore uses the electronic instrumentation to be important correctly. The survey electromagnetic interference’s appropriate instrument is the spectrum analyzer. The spectrum analyzer is one kind demonstrated the voltage amplitude along with the frequency shift rule the instrument, it demonstrated the profile is called the frequency spectrum. The spectrum analyzer has overcome oscilloscope’s in survey electromagnetic interference shortcoming, can in the precision measuring each frequency jamming intensity, be possible to demonstrate the signal directly with the spectrum analyzer each frequency spectrum component. When solution electromagnetic interference question, a most important question is judges the disturbance the origin. Only then after accurately noise source localization, only then can propose the solution disturbance measure. According to the signal frequency determined that the disturbance fountainhead is the simple the method, because in signal all characteristics, the frequency characteristic is stablest, and the circuit design personnel each spot’s signaling frequency are very often clear to the electric circuit. Therefore, so long as had known unwanted signal’s frequency, can extrapolate which spot the disturbance is produces. Regarding electromagnetic interference signal, because its scope often far is smaller than the normal work signal, makes this kind of survey with the spectrum analyzer is very simple. Because spectrum analyzer’s band width is narrow, can therefore filter with the unwanted signal frequency different signal, surveys the unwanted signal frequency precisely, thus judges produces the unwanted signal electric circuit. 2 electromagnetic compatibility trouble shooting technology (1) conduction question solution ①Through connects a high impedance to reduce the EMI electric current. ②Short-circuits through the parallel low impedance the EMI electric current to the place or directs other return route conductor. ③Shuts off the EMI electric current through the electric current shielding system. ④Suppresses the EMI electric current through its own function. (2) electromagnetic compatibility Rong Xing solution One kind of common phenomenon does not regard as filter electric capacity’s one side the impedance which separates with one to be directly connected, but regards as with the transmission line is connected. The typical situation is, when an input output line’s length achieves or surpasses 1/4 wave length, this transmission line changes “is long”. May use the equation below actually to express this kind of change approximately: l≥55/f In the formula: the l unit is the m, f unit is MHz. This formula had considered the average propagation velocity, it is free space theory 0.75 time. a. Dielectric medium material and tolerance The electromagnetic interference filter use the majority of electric capacities are the nonpolarity electric capacity. b. Bad mold (line to line) filter capacitive character electric capacity. c. The syntype (line arrives at/cabinet) the filter electric capacity The syntype (CM) the decoupling usually uses the small electric capacity (10~100nF). The small electric capacity may the high-frequency current which did not expect before it enters the sensitive electric circuit or when it is far to the noisy circuit short-circuits it to the cabinet comes up. In order to obtain the good high frequency damping circuit, reduces or eliminates the parasitic inductance is the key is. Therefore has the necessity to use the ultra short wire, especially hoped that uses the non-lead wire primary device. (3) perceptual, series loss electromagnetic compatibility solution Speaking of the electric capacity, Zs and Z1, if is not pure resistance, when calculates the frequency, must use their actual value. Capacitor series when power source or signal circuit, must satisfy: ①Winds through the operating current should not cause the inductance overheated or oversized goes beyond falls; ②Winds through the electric current cannot cause the inductance magnetic saturation, particularly to Gao Daoci the material is without a doubt. The solution has the following several kinds: * magnetic core material; * ferrites and load ferrites electric cable; * inductance, difference mold and syntype; * earth impedance coil; * combined inductance capacitance section. (4) radiation pattern question solution In many situations, the radiation electromagnetic interference question possibly produces in the conduction stage and is removed, but also has the solution is may the barrage jamming installment on the radiative transfer channel, shields such work on the image field. According to the shield theory, this kind of shield’s effect is mainly decided by the electromagnetism noise source frequency, and between the shielding system distance as well as the electromagnetic interference field characteristic - - electric field, the magnetic field or the plane wave. ①Conductor belt. The use copper either the aluminum belt want to establish one kind of direct shield and the low resistivity company fast simply connect or the main line. They regarding the temporary solution and the relatively permanent solution are very convenient. Thickness between 0.035~0.1mm, and back has the electric conduction adhesive in order to install. If the use copper electric conduction belt, it adopts the resistance approximately 20mΩ/cm2. Application situation: Electrical screening can; Breaks down when reveals designates the position; As an emergency solution, turns the plastic coupling the metal, the shield ordinary tape cable and so on. ②Netted shield belt and zipper type coat. Tu Xi steel mesh belt: Mainly uses for to install, in already assembled on the good electrical bill protective covering to take the bandage screening can which one kind easy to install. In order to reduce the electrical bill the magnetic field radiation or the sensitive issue, the steel mesh belt is one kind of effective solution. Zipper type shield coat: When has the obvious sign to indicate that the electrical bill is main causes time the EMI coupling reason uses. ③EMI gasket. Application situation: When following condition existence, and needs time true SE, the EMI gasket is the most commonly used solution radiation question, the sensitive issue, ESD, the electromagnetic pulse and the TEMPEST question method. * already confirmed engine case divulging for the main radiation way. * the mating surface is not very smooth, smooth or is not very hard, itself to be unable to provide the good connection contact. ④The window and passes air deflector’s EMI shield: Suits to the aperture shield. The plane wave general model is: SE≈104(-20-lgl)-20lgf In the formula, the SE unit is dB; l is the grid or the mesh size, the unit is mm; the f unit is MHz. Certainly, along with the frequency drop, the mesh shield efficiency SE upper limit is restricted in the metal itself. In the near zone field, to H shield, its shield power SHE the frequency influence, cannot obtain approximately by the equation below: SEH≈10lg (πr/l) And, r is the source to screening can between distance, l is the mesh size, both unit is mm. ⑤Conductive coating: Applies in establishes the EMI screening can, the transmission in system’s plastic outer covering existing ordinary either worsened electric conduction surface shield potency SE, prevents ESD or the static electricity accumulation phenomenon, increases the junction plane or the gasket seal contacted area. ⑥Electric conduction foil: The aluminum is one kind of good conductor, below 10MHz absorption loss, but it has the good reflection loss regarding electric field any frequency. The application situation please refer to the pertinent data. ⑦Electric conduction cloth: May apply in any 100kHz needs to achieve in the three-dimensional shield situation which to the GHz level frequency range 30~30dB weakens. 3 electromagnetic compatibility new component new material application 3.1 power line filter The power line filter install between the power line and the electronic installation, uses in electromagnetic interference which draws up in the electrical energy transmission to parasite, to enhances equipment’s reliability to have the influential role. The filter allow some frequencies to pass, but draws up to other frequency’s ingredient. According to parameters and load characteristics request and so on noise source characteristic, frequency range, voltage and impedance, suitable selective filter. 3.2 signal impediment transformer The pulse (digital either thyristor gate actuation) or in the simulation isolated-type transformer and the alternating current supply uses in the insulating transformer and the alternating current supply uses insulating transformer’s principle is the same, but the transmission band completely is actually different, the wanted signal processes to transformer’s some performance requirement (e.g. distortion, the 3dB band width, loss, symmetry, impedance, pulse time delay and so on) is strict. This kind of transformer belongs to the wideband equipment, the upper frequency achieves dozens of times with lowest frequency ratio fMAX/fMIN. Through in transmitting end or receiving end cut-off syntype ring circuit, insulating transformer while does not change the variation mold signal to draw up the syntype noise. Because the syntype voltage is adds in a transformer side, nearby two side two, this kind of disconnector must have the high breakdown voltage: The typical value is 1.5kV, certain situations reach as high as 10kV. The signal transformer’s principal advantage is it simple, durable, lasting and the linearity, moreover moderate cost. When the frequency increases, its electromagnetic compatibility performance drops. Application situation: * when needs the ring circuit isolates, its frequency range from cocurrent to several dozens MHz; * transmits when the low noise and the low distorted condition simulates the small signal (≤10mV), on the holding wire possibly exists several V to several kV syntype voltages; * in the thyristor application electric circuit, isolates the trigger driving circuit and the syntype voltage; * takes a scene solution, may use for to shut off a place ring circuit and to build a balanced connection or the non-balanced connection transmission line. 3.3 power source insulating transformer, power source manostat and UPS (1) power source insulating transformer The ordinary insulating transformer may shut off the main power line’s ground loop in the low frequency scope. When the frequency elevates, because the electrical isolation during a side checks electric capacity C1-2 the existence to drop. In order to reduce parasitic capacity’s influence, may use falls is, spiral-shaped, the separation-like and two windings, like this may reduce the parasitic capacity for originally for 1/3~/10. (2) Faraday shields the transformer In one time with the secondary coil between Bao Zhuo a aluminum foil or the copper foil, and causes it not with the coil contact, in order to avoid forms the short circuit. Faraday shields or the electric shield level earth. The application scope is as follows: * applies in entering the inner rooms the power source or in the power source distributor case, takes the simple 1:1 insulating transformer, isolates 50/60Hz the place ring circuit; * produces in identical system’s some part to the place maintains the neutral alternating current supply, maintains with the total power source distribution point the electricity isolates; * applies, when the system exists very in a big way to the floor drain copper current, prevents in the transition frequent triggering system’s earth fault detector; * may with the power line filter union use, the power line filter’s weaken characteristic only start above several dozens or several hundred kHz. 3.4 transition condition blankers The rheostat and the solid state rheostat (transzorbs) has the misalignment V-I characteristic curve part, may take the constant voltage part. When voltage after this component by clamp, in is equal to or is bigger than breakdown voltage VBR in the voltage value. This component’s speed of response is quick, but has certain limit in the processing energy content. 3.5 joining, the earth continuity and reduce the RF impedance component ①Earth sleeving or metal band width, but the flat wire compared to similarly transverse accumulates the round conductor has the small inductance. As the first choice reference, may use: * flat strap; * has the flat earth terminal flat sleeving; * circular, the many stranded wires jump the line. ②The print circuit wafer (PCB) earths the filling piece. In order to establish a more direct low obstuction electromagnetic interference electric current receiver, needs to use the earth filling piece. Usually has a spring clip among the resin filling piece, on the other hand with by and adds PCB in the one hand OV copper plate to install on the chassis to provide the strong reliable pressure. Because the spring is the copper tin material makes, the electricity contact performance is good, contact resistance for mΩ magnitude. ③Metal electrical bill trunking and fat altogether metal sleeving. The metal electric cable bracket, the public wire and the metal sleeving’s function transmits between several interconnection equipment’s partial earthing EMI circulation. May regard as it is between the different chassis or the grounding syntype short circuit channel, but in fact or exchanges 50/60Hz except the cocurrent, this method cannot apply in the long distance; May use in the computer room, the factory workshop or other has many non-shield electrical bill large-scale location, impossible either changes into very difficultly them the shield electrical bill or loads the pipeline. ④The impedance reduces, barrier height metal ledger wall earth liner. In order to reduce the conduction transient state disturbance the input and the environment radio frequency field to the system the influence, may through establish the indoor reference ground plate or the earth network improves. Through this method, may in reach as high as several hundred MHz in the frequencies to achieve 20dB very easily the improvement, may also reduce in the identical room between the different equipment’s place electric potential deviation. Another kind of technology: In the indoor, suggested the installment raises the metal ledger wall (RMF), takes the earth reference grid using the floor tile edge; Changes into the plastic absorption of shock filling piece the electric conduction absorption of shock filling piece, may establish, the lasting electrical connection very well. ②Temporary ground plate. After this kind, each solution is at first IBM Corporation’s installment plans engineers to use, namely the installment together copper plate or galvanizes the steel plate. Does not have “actually” the situation regarding these, because between the temporary ground plate and the building special structure has the big electric capacity (300~1000pF), this for the electromagnetic interference filter, the transient state protector and insulating transformer’s Faraday shielding layer provided had the absorption plant. In the high frequency end, this kind empty long, green or the olivine earth lead is more effective. Conclusion In actual EMC test application, besides through standard qualifications laboratory characterization test, but also two feasible methods are also are approved by the field: TCF (Technical Construction File) and Self Ceritification (self-checking proof). The antijamming ability test is the very practical test item. Realizes the electromagnetic compatibility the best means is, all digit and the analogous circuit will regard as to the high frequency signal response electric circuit, processes the electrical bill shield, the PCB wiring and the syntype filter with the high frequency design method. Uses the entire block horizon and the power source surface is also very important, to the analogous circuit also this so, does this is advantageous to the limit high frequency syntype link link. The majority transient state disturbances are high frequency, and has the very strong radiating capacity. |
