EMC Introduction
Prof. Tzong-Lin Wu NTUEE
What is EMC
Electro-Magnetic Compatibility EMC
Conducted Emission Radiated Emission Conducted Susceptibility
EMI
(Interference)
EMS
(Susceptibility) Radiated Susceptibility
Noise Source
Natural
Terrestrial Atmospheric Sun . . Man-Made ManBroadcast Radar Fluorescent lights Computing devices Microwave Ovens
Propagation Path
Radiation
Far-Field Plane Wave Near-Field Capacitate cross-talk Inductive cross-talk Conduction Power distribution Signal distribution Ground loops
Receptor
Biological
Man Animal Plants
Man-Made ManBroadcast receivers Navigation receivers Radar receivers Computing devices Biomedical sensors
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 destroyers radio system for communication with the UK would not operate properly while the ships 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.
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.
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 EMP 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.
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
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
Why EMC
High-speed trend reason: Year
2001 2004 2007 2010 2013 2016 pitch
(nm)
Vdd
1.1V 1.0V 0.7V 0.6V 0.5V 0.4V
on-chip speed 1.68GHz 3.99GHz 6.7GHz 11.5GHz 19.3GHz 28.7GHz
Power 130W 160W 190W 218W 251W 288W
150 90 65 45 32 22
Low voltage
High speed
High power consumption
(http://public.itrs.net)
*Source: The International Technology Roadmap for Semiconductor (ITRS), 2002
Why EMC
System on Package (SoP) SOC / SOP reason
RF IC Die
Edge radiation
Decoupling capacitor
Memory Die Memory Die
Signal trace
Digital signal Digital IC Die
Clock signal Ground Via
GBN coupling to signal via GBN source from through hole via digital signal
Ground plane Power plane GBN coupling to P/G via of RF IC Power via
Substrate GBN source from digital IC
Why EMC
Automobiles with electronics
Why EMC difficult to meet? (An example)
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Horizontal Polarization
Vertical Polarization Why ver < hor ?
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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
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How EMC
How EMC
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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.
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Decibels and Common EMC units.
a. dB 10l og10 dB 20l og10 dB 20l og10 P1 P2 v1 v2 I1 I2 for power for voltage for current the ratio of two quantity in dB.
b. dB V 20 log10
Volts 1 V ex : 1V = 120dB V 1mV = 60dB V
Volts Amps , dB A 20 log10 1mV 1 A Amps Watts dBmA 20 log10 , dB W 10 log10 1mA 1 W Watts d. Note : dBm dBmW 10 log10 1 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 m dB V 20 log10 1 V m m c. dBmV 20 log10 f. Gain in dB
Pin = 1W
Amplifier Gain=60dB
Pout ( Pout )dB W = ( Gain )dB + ( Pin )dB W
Pout = 60dB W
Pin = Gain Pout
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g. Power loss in Cables basic transmission line.
Iin
I(z)
I out
+
Vin
+
V(z)
+
Vout
Note X is the phasor expression (complex)
ZL
z=0
+
z=L
V( z ) = V e z e j z + V e + z e + j z = V f ( z ) + V b ( z ) I( z ) = V
+
z j z
e + z e + j z =
Vf ( z) ZL
Vb ( z) ZL
ZL
ZL
reflection coef.
( z ) = ( z ) =
Vb ( z) Vf ( z)
V V
e 2 z e j 2 z = 0 if Z L = Z C matched load Vb ( z) = 0
ZL Z C Z L + ZC
power delivered :
* 1 Re V( z )I ( z ) 2 if matched load
P av ( z ) =
1 V + 2 z e P av ( z ) = cos z where z = 2 ZC
2
ZC
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power loss for cables :
(cable loss)=
Pav ( z = 0) Pin = = e 2 L Pav ( z = L) Pout f
cable length
(cable loss)dB = 10 log10 e 2 L = 20 L log10 e = 8.686 L In general: is due to the loss of conductor
ex :
for cable RG-58U cable loss=4.5 dB 100 ft.
r = 2.1(Teflone)
coaxial cable
h. Signal Source Specification
Signal Source 50 Signal measurer
ZC
exSignal Generator equivalent circuit
Spectrum Analyzer
RS
ZC = 50
VOC
Cin
R in
Generally in industrial standard, R S =ZC =R in =50
for RF instrument
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Output power displayed on a meter of the signal source in terms of output power of matched load. i.e R L = R S = 50 Vout RL 1 = VOC = VOC RS + R L 2 Vout V = out RL 50
2 2
RS VOC
Pout =
+ Vout -
RL
Note : It is industrial standard that voltage and currents are specified in their RMS values and no factor of then required in power expression. i.e. Vout = 1 (Vout ) peak. 2 1 is 2
for examplea S.G. shows -37dBm output means Vout = 50 i Pout = 3.162mv(RMS) = 70dB V
Many signal measures such as spectrum analyzers also have their response specified assume a 50 input impedance to the instrument. for examplea S.A. shows the maximum input rating of -30dBm=1 W (Vin ) max = 50 i Pin = 50() i 1( W) = 7.07mv
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