Introduction to Electromagnetic Compatibility Chapter 1 Introduction to Electromagnetic Compatibility Introduction to Electromagnetic Compatibility / C. R. Paul

Aspects of EMC

3 criteria for electromagnetic compatibility

3 ways to prevent interference

Basic EMC subproblem： (a) radiated emissions

Basic EMC subproblem： (b) radiated susceptibility

Basic EMC subproblem： (c) conducted emissions

Basic EMC subproblem： (d) conducted susceptibility

Electrostatic discharge (ESD)

Electromagnetic pulse (EMP)

Lightning

Secure communication and data processing (TEMPEST)

History of EMC Examples

History of EMC Since 1920 FCC IEC CISPR MIL-STD-461

Examples UK Destroyer-HMS Sheffield USA Helicopter-UH-60 Black Hawk USA Aircraft Carrier-Forrestal

Electrcal Dimensions and Waves

Effect of element interconection leads

Time delay Free Space：3ns/1m。 3G Hz Transitioning time=100~500 ps。 Propogation velocity in glass epoxy=1.8108m/s。 6-in time delay=850 ps。

Current propagation Phase shift Z：position。 ：phase constant (radians per meter)。 ：2f (radians per second )。 Phase shift ：phase shift。 L：total length

Wave propagation  =  z

The movement of a point on the waveform Wave length ：wave length。 The movement of a point on the waveform

Wave propagation as time progresses

The velocity of wave movement Differentiating Wavelength

Phase shiftTime delay One wavelength Phase shift of 360 degrees

Frequency bands

Constants

Velocity of propagation in free space Velocity of propagation in nonconductive media

Wave propagation in Teflon (r=2.1, r=1)

Exercise

Why decibel ? Decibels have the propoty of compressing data. dB

Decibels and Common EMC Units

The use of the decibel(dB)：Power gaindB

Voltage gaindB & Current gaindB

Exercise

Referenced to some base quantity

Conversion

Exercise

Decibel for EMC

Exercise

Conversion to Decibels

Exercise

The use of the decibel in computing amplifier performance

Power Loss in Cables

Transmission line equations (forward & backward travelling wave)

Time domain equations (forward & backward travelling wave)

Voltage reflection coefficient Reflection coefficient at load

Equation relation

Matched line Without backward travelling wave

Average power delivered to position z (matched line) Input power/output power (matched line)

Power loss in the cable (2 definitions, matched line)

Signal Source Specification

Signal source as a Thevenin equivalent circuit

An equivalent circuit for the signal measurer

Use of coaxial cables with matched loads

Calculation of a signal source output If

Example (1), matched load

Example (2), matched load Can obtain a relation：-37+107=70 For example：-40dBm+10767dBV

Question 107?

Example Another method

Example (3), matched load

Example (4), unmatched load Method 1 Method 2

Example (5), signal measured by signal measurer Method #1 OR

Method #2 107-30=77

Exercise

Exercise