Transcript 2. Near field coupling

Electromagnetic interference
Done by
‫عماد خليل العجلة‬
‫عالء خليل العجلة‬
Instructor
‫محمد عودة‬.‫د‬
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Outline
 Source and victim
 Emissions
 Immunity
 Causes of internal radar interference
 External radar interference
 EMC design
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Interference coupling mechanisms
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Interference coupling mechanisms
source
victim
coupling path
Direct
coupling
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Near field
coupling
Radiated
coupling
coupling path
1. Direct coupling
Coupling via power
or signal lines
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Common impedance
coupling
1. Direct coupling
Coupling via power
or signal lines
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1. Direct coupling
Common impedance
coupling
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coupling path
2. Near field coupling
Magnetic or
inductive coupling
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Electric or
capacitive coupling
2. Near field coupling
Magnetic or
inductive coupling
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2. Near field coupling
Electric or
capacitive coupling
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2. Near field coupling
 Spacing
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coupling path
3. Radiated coupling
Field generation
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Wave impedance
coupling path
4. Coupling modes
Differential
mode
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Common mode
Antenna mode
Coupling modes
Differential
mode
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Coupling modes
Common mode
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Coupling modes
Antenna mode
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Interference coupling mechanisms
Emissions
Radiated
emission
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Conducted
emission
Emissions
Radiated
emission
 Radiation from the PCB
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Emissions
Radiated
emission
 Radiation from cables
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Interference coupling mechanisms
Immunity
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Causes of internal radar interference
Standards used : MIL-HDBK-237
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What is jamming [2]
 jamming is a form of Electronic Warfare where jammers radiate
interfering signals toward an enemy's radar, blocking the receiver with
highly concentrated energy signals
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 jammers can be categorized into two general types:
1- barrage jammers
2- deceptive jammers (repeaters).
 Barrage jammers attempt to increase the noise level across the
entire radar operating bandwidth.
 Barrage jammers are often called maskers
 Barrage jammers can be deployed in the main beam or in the side
lobes of the radar antenna
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 Repeater jammers carry receiving devices on board in order to
analyze the radar’s transmission, and then send back false targetlike signals in order to confuse the radar
 There are two common types of repeater jammers:
1- spot noise repeaters
2- deceptive repeaters
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Spot and Barrage Jamming
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Self-Screening Jammers (SSJ) [2]
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Self-Screening Jammers (SSJ)
 The single pulse power received by the radar from a target of RCS , at range
, is
 The power received by the radar from an SSJ jammer at the same range is
 BJ > Br jammer bandwidth is usually larger than the operating bandwidth of
the radar.
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 S/J ratio for a SSJ
 The jamming power is generally greater than the target
signal power.
 The ratio s/j is less than unity.
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 As the target becomes closer to the radar, there will be a certain range
such that the ratio s/j is equal to unity.
 This range is known as the cross-over range.
 The range window where the ratio S ⁄j is sufficiently larger than unity
is denoted as the detection range.
 In order to compute the crossover range
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For a radar with a detection range of 100 km for an RCS of 5m2, [3]
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This program calculates the cross-over range and generates plots of
relative S and J versus range normalized to the cross-over range
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Wave length
in dB
Conversion to db
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By matlab
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Stand-Off Jammers (SOJ)
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Stand-Off Jammers (SOJ)
 ECM signals from long ranges.
 The power received by the radar from an SOJ jammer at range RJ
is
 The gain term G’ represents the radar antenna gain in the
direction of the jammer
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The inputs to the program ‘soj_req.m’ are the same as in the SSJ case , with
jammer peak power Pj = 5000w , jammer antenna gain Gj =30 dB, radar antenna
gain on the jammer G’ =10dB, and radar to jammer range R= 22.2 Km
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EMC design
 There are many design considerations that need to be taken
 Cable wiring
 Connectors
 Grounding
 Shielding
 The reference for good consideration is standard
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What is FEKO program?
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Cable coupling analyses
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Cable coupling analyses
 The result
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EMC analysis of a wire inside a
metallic box
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Cont.
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Reference
 [1] H.-D. Brüns, H. Singer, “Computation of Interference in Cables Close to
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Metal Surfaces,” IEEE Int. Symposium on EMC, Denver, 1998, pp 981-986
[2] CRC Press - MATLAB Simulations for Radar Systems Design
[3] Air and Space borne Radar Systems - An Introduction
[4] Intro duction to airborne radar second edition George W. stimson
[5] Tim Williams, EMC for Product Designers, Fourth edition
[6] CLAYTON R. PAUL, Introduction to Electromagnetic Compatibility,
Second Edition
[7] Frank H. Sanders Effects of RF Interference on Radar Receivers
[8] EMI from Cavity Modes of Shielding Enclosures – FDTD Modelling and
Measurements,” M. Li, J. Nuebel et al, IEEE Trans on EMC,Vol. 42, No. 1, February
2000, pp. 29-38.