EMC Introduction. What is EMC. EMS (Susceptibility) Electro-Magnetic Compatibility EMC. Conducted Emission EMI. Conducted Susceptibility

Transcription

1 EMC Introduction Prof. Tzong-Lin Wu NTUEE What is EMC Electro-Magnetic Compatibility EMC Conducted Emission EMI (Interference) Radiated Emission EMS (Susceptibility) Conducted Susceptibility Radiated Susceptibility 1

2 2

3 Noise Propagation Receptor Source Path Natural Radiation Biological Terrestrial Far-Field Man Atmospheric Plane Wave Animal Sun Near-Field Plants. Capacitate cross-talk. Inductive cross-talk Man-Made Made Conduction Man-Made Made Broadcast Power distribution Broadcast receivers Radar Signal distribution Navigation receivers Fluorescent lights Ground loops Radar receivers Computing devices Computing devices Microwave Ovens Biomedical sensors 3

4 What is EMC EMI In 1982 the U.K. lost a destroyer ( ) in the battle of Falkland Island during the engagement with Argentinean forces. The destroyer s radio system for communication with the UK would not operate properly while the ship s anti-missile detection was being operated. What is EMC EMI A new version of an automobile has microprocessor-controlled emission and fuel monitoring system installed. When the customer drove down a certain street in the town, the car would stall. The illegal FM radio in this street cause that. 4

5 What is EMC EMI FM/AM radio is noisy when the Desktop PC is turned on. It is forbidden to use the electronic devices, such as wireless phone, notebook, on the airplane. What is EMC : Examples EMS Walking across a nylon carpet with rubbersoled shoes can cause a build-up of static charge on the body. When an electronic device is touched, an ESD occurred. A protection system for ESD is required. 5

6 What is EMC EMS In the first nuclear detonation in the mid-1940s, it was discovered that semiconductor devices that was used to monitor the blast were destroyed. It is due to the intense EM wave (EMP) created by the charge separation and movement within the detonation. What is EMC EMS Lighting carries upwards of 50,000A of current. The EM fields from this intense current can couple to electronic systems either by direct radiation or coupling. 6

7 What is EMC? Electromagnetic Compatibility (EMC) Low Electromagnetic Interference (EMI) Conducted & Radiated Low Electromagnetic Susceptibility (EMS) ESD, Surge, Fast Transient Good Signal Quality/Integrity (SI) Why EMC Healthy reasons: Microwave oven GSM for brain tumor Cancer caused by high power line Safety reasons Aircraft navigation Appliance in home 7

8 Safety and Health Why EMC Wireless comm. reasons clear spectrum is necessary for WCOM. For proper and secure data transmission. Wide spectrum usage such as AM radio in LF, MF and HF range FM, TV, and mobile phone in VHF GPS, Digital sound broadcasting in UHF Satellite communication in Microwave range 8

9 Why EMC High-speed trend reason: Year ½pitch (nm) V dd on-chip speed Power V 1.68GHz 130W V 3.99GHz 160W V 6.7GHz 190W V 11.5GHz 218W V 19.3GHz 251W V 28.7GHz 288W Low voltage High speed High power consumption *Source: The International Technology Roadmap for Semiconductor (ITRS), 2002 ( Why EMC SOC / SOP reason System on Package (SoP) Decoupling capacitor Memory Memory Die Die Signal trace Edge radiation Digital signal RF IC Die Clock signal Digital IC Die GBN coupling to signal via Ground Via Ground plane Power plane GBN coupling to P/G via of RF IC Power via GBN source from digital IC GBN source from through hole via digital signal Substrate 9

10 Why EMC Automobiles with electronics Why EMC difficult to meet? (An example) 10

11 Horizontal Polarization Vertical Polarization Why ver < hor? 11

12 How EMC Source (Emitter) Cost: Low Transfer (Coupling) Path middle Receptor (Receiver) high Suppress the emission at its source Make the coupling path as inefficient as possible Make the receptor less susceptible to the emission How EMC 12

13 How EMC How EMC 13

14 How EMC An example: for PC Suppress the emission: Proper layout with EM concept using component with low edge rate as possible Reduce coupling path using shielded enclosure less susceptible receptor differential pairs error-correcting code 2) EMC technique include three levels. First ( Basic ) --- After the development of product is completed, we can do all standard EMC tests following the regulations --- When they can not pass, you can fix the problems by adding components. ( Such as cap, choke ) Second ( Middle ) --- In the testing phase, by the knowledge of EMC, the EMC problem can be found and the design can be changed before mass production. --- at this level, only the subparts can be changed, but the architecture of the system can not be changed. Third ( Advanced ) this course --- In the design stage, the EMC experience, knowledge, and the simulation tool are well employed to design the architecture of the system, you know all what if conditions. 14

15 Decibels and Common EMC units. a. l P 1 db 10 og 10 for power P2 l 1 db 20 og 10 for voltage the ratio of two quantity in db. v2 l 1 db 20 og 10 for current I2 b. dbµ V 20log10 1 V v I Volts µ ex : 1V = 120dBµ V 1mV = 60dBµ V c. dbmv 20 log Volts, dbµ A 20 log 1mV dbma 20 log Amps, dbµ W 10 log 1mA Watts d. Note : dbm dbmw 10log 10 1 µ W Amps 1µ A Watts 1µ W e. In EMC, radiated EM fields are expressed in terms of electrical field intensity in V/m, or in terms of magnetic field in units of A. m V dbµ V 20log m m 10 1 µ Vm f. Gain in db Pin = Gain Pout Pin = 1µ W Pout ( Pout ) = ( Gain) + ( Pin ) dbµ W db dbµ W Amplifier Pout = 60dBµ W Gain=60dB 15

16 g. Power loss in Cables basic transmission line. I in I( z) V in V( z) I out V out Note X is the phasor expression (complex) ZL z=0 z=l z + αz jβz + αz + jβz V( z) = V e e + V e e = V f( z) + V b( z) + V V V αz jβz + αz + jβz f( z) V b( z) I( z) = e e e e = Z Z Z Z L L L L reflection coef. V() b z V 2αz j2βz Γ ( z) = = e e + V() f z V ZL Z C Γ ( z) = Z L + ZC Γ= 0 if Z L = Z C matched load V b( z) = 0 power delivered : 1 * P ( ) Re V( av z = z) I( z) 2 if matched load 2 + 1V 2α z P ( ) cos where av z = e θz θz = Z 2 Z C C 16

17 power loss for cables : P av ( z = 0) Pin 2α L (cable loss)= = = e cable length P av ( z = L ) P out 2α L (cable loss) = 10log e = 20α Llog e= 8.686α L db In general α is due to the loss of conductor ex : for cable RG-58U cable loss=4.5 db 100 ft. ε r = 2.1(Teflone) coaxial cable f h. Signal Source Specification Signal Source ex Signal Generator equivalent circuit RS 50 Z C ZC = 50Ω Signal measurer Spectrum Analyzer V OC C in R in Generally in industrial standard, R =Z =R =50 Ω for RF instrument S C in 17

18 Output power displayed on a meter of the signal source in terms of output power of matched load. i.e R = R = 50Ω L S R 1 V = V = V L out OC OC RS + RL out Vout V Pout = = R 50 L out out peak. R S V OC V out Note : It is industrial standard that voltage and currents are 1 specified in their RMS values and no factor of is 2 then required in power expression. 1 i.e. V = (V ) R L for example a S.G. shows -37dBm output means V = 50 i P = 3.162m v (RMS) = 70dBµ V out out Many signal measures such as spectrum analyzers also have their response specified assume a 50 Ω input impedance to the instrument. for example a S.A. shows the maximum input rating of -30dBm=1µ W (V ) = 50 i P = 50( Ω ) i1( µ W) = 7.07mv in max in 18