Done by عماد خليل العجلة علاء خليل العجلة Instructor د. محمد عودة Electromagnetic interference 1

Outline Source and victim Emissions Immunity Causes of internal radar interference External radar interference EMC design 2

Interference coupling mechanisms 3

coupling path Direct coupling Radiated coupling Near field coupling 4 sourcevictim

coupling path 1. Direct coupling Coupling via power or signal lines Common impedance coupling 5

1. Direct coupling Coupling via power or signal lines 6

1. Direct coupling Common impedance coupling 7

coupling path 2. Near field coupling Magnetic or inductive coupling Electric or capacitive coupling 8

2. Near field coupling Magnetic or inductive coupling 9

2. Near field coupling Electric or capacitive coupling 10

2. Near field coupling Spacing 11

coupling path 3. Radiated coupling Wave impedanceField generation 12

coupling path 4. Coupling modes Antenna modeCommon mode Differential mode 13

Coupling modes Differential mode 14

Coupling modes Common mode 15

Coupling modes Antenna mode 16

Interference coupling mechanisms Emissions Radiated emission Conducted emission 17

Emissions Radiation from the PCB Radiated emission 18

Emissions Radiation from cables Radiated emission 19

Interference coupling mechanisms Immunity 20

Causes of internal radar interference 21 Standards used : MIL-HDBK-237

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 22

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 23

Repeater jammers carry receiving devices on board in order to analyze the radar’s transmission, and then send back false target- like signals in order to confuse the radar There are two common types of repeater jammers: 1- spot noise repeaters 2- deceptive repeaters 24

Spot and Barrage Jamming 25

Self-Screening Jammers (SSJ) [2] 26

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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 B J > B r jammer bandwidth is usually larger than the operating bandwidth of the radar. 28

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. 29

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 30

For a radar with a detection range of 100 km for an RCS of 5m 2, [3] 31

This program calculates the cross-over range and generates plots of relative S and J versus range normalized to the cross-over range 32

Wave length in dB Conversion to db 33

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By matlab 35

Stand-Off Jammers (SOJ) 36

Stand-Off Jammers (SOJ) ECM signals from long ranges. The power received by the radar from an SOJ jammer at range R J is The gain term G’ represents the radar antenna gain in the direction of the jammer 37

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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 39

EMC design There are many design considerations that need to be taken Cable wiring Connectors Grounding Shielding The reference for good consideration is standard 40

What is FEKO program? 41

Cable coupling analyses 42

Cable coupling analyses The result 43

EMC analysis of a wire inside a metallic box 44

Cont. 45

Reference [1] H.-D. Brüns, H. Singer, “Computation of Interference in Cables Close to Metal Surfaces,” IEEE Int. Symposium on EMC, Denver, 1998, pp [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