KF 1063

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KF 1063 LECTURE 13
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CONTENTS

• Circuit Interference
• EMC
• RFI
• EMI
• Methods of Avoiding Circuit Interference
• Noise

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INTRODUCTION

• Electromagnetic Compatibility EMC The ability
  of a product coexist in its electromagnetic
  environment without causing or suffering
  functional degradation or damage
• Emissions propagation of electromagnetic
  interference (EMI) from noncompliant devices and
  in particular radiated and conducted radio
  frequency interference (RF)
• Susceptibility The detrimental effects on
  susceptible devices (victims) of EMI in forms
  that include electrostatic discharge (ESD) and
  other forms of electrical overstress (EOS)
• EMC Regulatory
• North American FCC (Federal Communication
  Commission, US) DOC (Department of
  Communication, Canada )
• Worldwide IEC (International Electrotechnical
  Commission)
• European Union IEC and CISPR (International
  Special Committee on Radio Interference)

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EMC
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EMI

• Electromagnetic Interference, EMI A process by
  which disruptive electromagnetic energy is
  transmitted from one electromagnetic device to
  another via radiated or conducted paths (or
  both).
• EMI can propagate by two means
• By radiation - where the energy can be coupled
  either through magnetic or electric field or as
  an electro-magnetic wave between the source and
  the victim.
• By conduction - where the EMI energy will
  propagate along power supply cable and the power
  source.
• EMI sources
• Rectifying diodes
• Switching components (IGBTs)
• High frequency transformers and chokes
• Circuit layouts (high dv/dt long wires, high
  dv/dt wide loops, high current wires)
• Mechanical switches bouncing

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EMI
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RFI

• Radio Frequency Interference, RFI
  Electromagnetic radiation which is emitted by
  electrical circuits carrying rapidly changing
  signals, as a by-product of their normal
  operation, and which causes unwanted signals
  (interference or noise) to be induced in other
  circuits
• Radio Frequency Interference (RFI) is considered
  as part of the EMI spectrum, with interference
  signals being within the radio frequency (RF)
  range. This term was once used interchangeably
  with EMI.

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EMI/RFI
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EMI/STANDARD

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PROTECTION
Ferrite Core
Shielding
Main Filters
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EMI/RFI PROTECTION

• Physical Isolation Devices that emit
  electromagnetic radiation should be kept a
  reasonable distance from your PC, peripherals and
  media. This includes television sets, radios,
  lights, kitchen appliances, and stereo speakers
  (the ones designed for use with PCs are generally
  shielded and are much less of an issue).
• Use Dedicated Circuits Many office buildings
  especially, have separate power circuits that are
  intended for use by PCs. Keeping your PC on a
  circuit that is separate from the circuit running
  your refrigerator and air conditioning unit means
  that there will be much less interference passing
  to the computer from the other devices (and this
  will also improve the quality of the power being
  sent to your machine in general).
• Power Conditioning The use of a line conditioner
  or uninterruptible power supply can filter out
  interference caused by other devices that share a
  line with your PC.

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INTERFERENCE
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EMI/RFI
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EMI/RFI
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EMI/RFI
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EMI/RFI
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EMI/RFI
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EMI/RFI
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EMI/RFI
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to the 16th Edition IEE Regulations
to the 16th Edition IEE Regulations


Fig 5.1 - Three-phase delta/star transformer
showing earthing arrangements
Fig 5.1 - Three-phase delta/star transformer
showing earthing arrangements
SIGNAL AND NOISE

• Isyarat (Signal) merupakan apa yang diukur dari
  punca bekalan isyarat sementara Hingar (Noise)
  pula merupakan maklumat tambahan yang boleh
  menggangu dan mengubah sesuatu isyarat.
• Hingar bersifat ketaktentuan dan rawak serta
  tidak boleh dihapuskan (eliminate) tetapi boleh
  diminimumkan.
• Memandangkan hingar tidak boleh dihapuskan, maka
  biasanya Nisbah Isyarat-ke-Hingar (SNR) sering
  diambil kira.

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to the 16th Edition IEE Regulations
to the 16th Edition IEE Regulations


Fig 5.1 - Three-phase delta/star transformer
showing earthing arrangements
Fig 5.1 - Three-phase delta/star transformer
showing earthing arrangements
ISYARAT DAN HINGAR
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to the 16th Edition IEE Regulations
to the 16th Edition IEE Regulations


Fig 5.1 - Three-phase delta/star transformer
showing earthing arrangements
Fig 5.1 - Three-phase delta/star transformer
showing earthing arrangements
HINGAR

• Hingar Kimia (Chemical Noise)
• tindakan kimia yang tak diingini
• tindakan/teknik/peralatan yang tertentu
• Hingar Peralatan
• memberi kesan ke atas peralatan
• boleh dikawal secara fizikal (suhu) atau
  elektronik (perisian)
• Hingar Haba (Johnson)
• Thermal agitation of electrons affects their
  smooth flow
• Due to different velocities and movement of
  electrons in electrical components.
• Dependent upon both temperature and the range of
  frequencies (frequency bandwidths) being
  utilized.
• Can be reduced by reducing temperature of
  electrical components.
• Eliminated at absolute zero.
• Considered white noise occurs at all
  frequencies.
• ?pmk (4kTR?f)1/2

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to the 16th Edition IEE Regulations
to the 16th Edition IEE Regulations


Fig 5.1 - Three-phase delta/star transformer
showing earthing arrangements
Fig 5.1 - Three-phase delta/star transformer
showing earthing arrangements
HINGAR

• Hingar Shot (Shot Noise)

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Decibels (dB)
YdB 10 log (x) where x is in power units
(Watts) YdB 10 log (10) 10 dB YdB 10 log
(100) 20 dB YdB 10 log (20) 13 dB
YdB 10 log (v2) for voltage across say 1W
resistor YdB 20 log (v)
Decibels represent 1. Level (absolute or
relative) 2. Ratio (gain or loss)
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Decibels (Level)
The RF output power level of a transmitter is
specified in dBm (microwave radio) or dBw (mobile
radio).
Example Microwave radio transmitter 30 dBm (1
W) Mobile radio base station transmitter 20 dBw
(100 W)
dBw 10 log (P/1W) dBm 10 log (P/1mW)
1 Watt 0 dBw 1 m Watt 0 dBm
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Examples of dBw and dBm
1 W 2 W 4 W 8 W 16 W
0 dBw 3 dBw 6 dBw 9 dBw 12 dBw
30 dBm 33 dBm 36 dBm 39 dBm 42 dBm
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Decibels (Ratio)
Pi Vi Ii
Po Vo Io
System
dB 10 log (Po/Pi) power ratio dB 20 log
(Vo/Vi) voltage ratio dB 20 log
(Io/Ii) current ratio
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Noise Factor / Figure
Linear System
Si/Ni
So/No
Noise Factor (f) (S/N) i / (S/N) o
Noise Figure (NF) 10 log ( f )
Note Signal and Noise are in Power Unit
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Noise Figure
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Noise Figure
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Two loudspeakers emit waves with l 2.0 m.
Speaker 2 is 1.0 m in front of speaker 1. What,
if anything, must be done to cause constructive
interference between the two waves?
1. Move speaker 1 backward (to the left) 0.5
m. 2. Move speaker 1 backward (to the left) 1.0
m. 3. Move speaker 1 forward (to the right) 1.0
m. 4. Move speaker 1 forward (to the right) 0.5
m. 5. Nothing. The situation shown already causes
constructive interference.
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Two loudspeakers emit waves with l 2.0 m.
Speaker 2 is 1.0 m in front of speaker 1. What,
if anything, must be done to cause constructive
interference between the two waves?
1. Move speaker 1 backward (to the left) 0.5
m. 2. Move speaker 1 backward (to the left) 1.0
m. 3. Move speaker 1 forward (to the right) 1.0
m. 4. Move speaker 1 forward (to the right) 0.5
m. 5. Nothing. The situation shown already causes
constructive interference.