EMC Near-Field Scanning

Searching for Root Causes

Nov. 01, 2018Proprietary Information - Do not duplicate or distribute without written permission from Amber Precision Instruments (API).

© 2018 Amber Precision Instruments, Inc. (API)

EMC Compliance

1* https://twitter.com/elonmusk/status/998409778316496896

Outline

• Susceptibility Scanning

– Conducted susceptibility: where does ESD current go?

– Near-field effects of electrostatic discharge events

• Emission Scanning

– Sniffer probes are smarter than they look

– Electromagnetic lens: from near-field to far-field

2

ESD Susceptibility Scanning

3

Electrostatic Discharge (ESD)

4

DUT

Human Body Model

(HBM)

R = 1500 Ω

C = 100 pF

DUT

Human Metal Model

(HMM)

R = 330 Ω

C = 150 pF

HBM Waveform

5* ANSI/ESDA/JEDEC JS-001-2010, MIL-STD-883J Method 3015.9

** https://www.thermofisher.com/order/catalog/product/CUSPID0000019

HMM Waveform

6* IEC 61000-4-2, ISO 10605, MIL-STD-461G CS118, ANSI/ESD SP5.6-2009

ESD Current Spreading Scanning

7

Robot

DUT

TLP

Scope

Pro

be

PC

Results

* IEC TS 61967-3

Current Spreading on Microstrip

8

Current Spreading on Microstrip

9

Current Spreading on Flex PCB

10

Current Spreading on Flex PCB

11

ANSI/ESD SP14.5-2015

12

From ESDA:

For Electrostatic Discharge Sensitivity Testing –

Near-Field Immunity Scanning –

Component/Module/PCB Level

An American National Standard

Approved September 14, 2015

ESD scanning technology is widely accepted as a powerful tool for root cause

analysis and screening high immunity components, modules and systems

* ANSI/ESD SP14.5-2015

ESD Immunity Scanning

13

Robot

TLP

PC

DUTP

robe

Results

FD

* ANSI/ESD SP14.5-2015, IEC 61000-4-2, ISO 10605, MIL-STD-461G CS118, ANSI/ESD SP5.6-2009

TLP Waveform

14

VTLP = 2 kV

Tr = 500 ps

Tf = 33 ns

Current Waveforms:

HBM vs HMM vs TLP

15

Simulated discharge current

waveform on 2 Ω load

* IEC 61000-4-2

HMM vs ANSI/ESD SP14.5-2015

Simple Structure

16

?

50 ohms microstrip (3 mm wide trace)

Board dimension: 100 x 100 mm2

Board elevation from HCP: 1 mm

ESD generator distance to board: 10 mm

ESD generator setting: 2 kV CD

50 ohms microstrip (3 mm wide trace)

Board dimension: 100 x 100 mm2

Probe: 2 mm or 5 mm loop H-field

Mechanical probe height from trace: 0 mm

TLP setting: 2 kV

Field Coupling to Microstrip

17

H-Field E-Field

Surface Current Density

Field Coupling to Microstrip

18

H-Field E-Field

Surface Current Density

Field Attenuation from ESD

19

HMM vs Near-Field Injection

20

What Does Happen during Discharge?

21

Enclosure

PCB

PCB

Flex cable

ESD Generator

Connector

ICFAILED!

FAILED!

Near-Field Probe Reproduces HMM Results

22

FAILED!

-5 0 5 10 15 20 25 30 35 400

500

1000

1500

2000

2500

3000

3500

Time [ns]

Vo

ltag

e [V

]

TLP

Electromagnetic field is coupling to traces or IC

FAILED!

Electromagnetic field is coupling to flex cable and induces current

TLPWaveform

Near-FieldProbe

Effect of PCB Layout on

Susceptibility

23

PCB Layout 1* PCB Layout 2*

Hx

Hy

* Two functionally identical boards with different PCB layouts. Layout 1 fails at higher voltages during gun test.

Effect of IC Fab on Susceptibility

24

White Paper 3 Part II specifically covers in detail an overview of system ESD stress application methods, system diagnostic techniques to detect hard or soft failures, and the application of tools for susceptibility scanning. For example, as illustratedin Figure 2, these types of advanced tools can be used to differentiate thecharacteristics of products and enable proper system protection methodology*.

Figure 2: Susceptibility scanning using pulse techniques on Product A (left) and Product B (right) (Courtesy of Amber Precision Instruments)

* From the ESDA White paper 3, Part II, page 18.

** Product A and Product B are functionally identical ICs from different vendors.

Susceptibility Scanning: Conclusion

• Conducted susceptibility to an ESD event can be

analyzed by measuring and visualizing scanned

surface current density on the DUT.

• Susceptibility to near-field effects of an ESD

event can be emulated with near-field injection.

• Near-field injection per ANSI/ESD SP14.5-2015

reproduces same failures as IEC 61000-4-2.

25

Electromagnetic Compatibility (EMC)

26

Aggressor Victim

Conducted

Emission

Conducted

Susceptibility

Radiated

Susceptibility

Radiated

Emission

27

Emission Scanning

Sniffer Probe

28* Hand-made

EMI Near-Field Probe

29

Probes:- Up to 40 GHz- Down to 20 kHz

Optional EMI Probes;Choose:- Size- Frequency range- Field Component

* EMI Hx 2 mm

EMI Near-Field Scanning

30

Robot

DUTP

robe

PC

SA

Results

* IEC TS 61967-3

Phase Measurement Scanning

31

Robot

DUTP

robe

PC

VNAor

Scope

ResultsRef Probe

* IEC TS 61967-3

Applications of Phase Measurement

32

Applications

of Phase

Measurement

Near-Field to

Far-Field

Emission Source

Microscopy (ESM)

RFI and Source

Modeling

Source

Localization

Applications of ESM:

- High speed data communication

- Data centers, servers, routers, cloud

- 5G mobile network, IoT

- Radar systems

- Phased arrays

- Electrically large, automotive, aerospace

Co-Design:

Measurement and Simulation

33

History of ESM:

Synthetic Aperture Radar (SAR)

34

Measuring instrument

Antenna

SUT

Scanning plane

Use of imaging algorithm on

measured data

Applications of SAR:

- Airborne radar

- Medical imaging

- Concealed object detection

- Non-destructive testing

- Antenna diagnosis

* Wikipedia, P.L. Ransom et al (1971), J.J Lee et al (1988), M. Soumekh (1991), D.M. Sheen et al (2001), B. Janice (2011), H. Kajbaf et al (2013)

MR

I

Angio

gra

phy

Venus

Magellan Probe2.385 GHz, 12.6 cm

Symmetric Differential Microstrip

35

Full-wave simulation

Differential microstrip line

Differentially driven @ 10 GHzEx @ Z=1 mm (λ/30)

Ex @ Z=30 mm (λ)Ex @ Z=7.5 mm (λ/4)

Non-I

nvert

ing

Invert

ing

Load

Asymmetric Differential Microstrip

36

Non-I

nvert

ing

Invert

ing

Load

GND

Asymmetric differential microstrip

12 mil gap between GND & line

Differentially driven @ 10 GHzEx @ Z=1 mm (λ/30)

Ex @ Z=30 mm (λ)Ex @ Z=7.5 mm (λ/4)

Wave Propagation

37* Asymmetric differential microstrip @ 10 GHz

Ez

Ex Ey

|E|

Wave Propagation

38* Asymmetric differential microstrip @ 10 GHz

Ez

Ex Ey

|E|

Wave Propagation

39

Max Ex Max Ey

Max Ez Max |E|

* Asymmetric differential microstrip @ 10 GHz

Z=1 mm (λ/30)

Z=7.5 mm (λ/4)

Z=30 mm (λ)

Z=60 mm (2λ)

Wave Propagation

40

Max Ex Max Ey

Max Ez Max |E|

Z=1 mm (λ/30)

Z=7.5 mm (λ/4)

Z=30 mm (λ)

Z=60 mm (2λ)

* Symmetric differential microstrip @ 10 GHz

Emission Source Microscopy (ESM)

41

Measure at Radiative

Near-Field

(~1-2λ away from

DUT)

Back-Calculate to

DUT Location

(Phase Adjustment)*

Localize Sources

Contributing to

Far-Field

Optional:

Calculate TRP

Optional:

Calculate Far-Field

Pattern𝑓 𝑥, 𝑦 = 𝐹2𝐷

−1 𝐹2𝐷 𝑠 𝑥, 𝑦 𝑒−𝑗𝑘𝑧𝑧0 𝑘𝑧 = 𝑘2 − 𝑘𝑥2 − 𝑘𝑦

2

* Using Range Migration Algorithm (RMA) or Synthetic Aperture Radar (SAR)

k-Space and Propagating Wave

42

𝑓 𝑥, 𝑦 = 𝐹2𝐷−1 𝐹2𝐷 𝑠 𝑥, 𝑦 𝑒−𝑗𝑘𝑧𝑧0

* Asymmetric differential microstrip @ 10 GHz, Z=30mm (λ)

Scanned |Ex| k-Space Focused |Ex|

Scanned ∡ Ex ∡ k-Space Focused ∡ Ex

𝐹2𝐷 𝐹2𝐷−1

𝑒−𝑗𝑘𝑧𝑧0

𝑘𝑧 = 𝑘2 − 𝑘𝑥2 − 𝑘𝑦

2

k-Space and Evanescent Wave

43* Asymmetric differential microstrip @ 10 GHz, Z=1mm (λ/30)

Scanned |Ex| k-Space Focused |Ex|

Scanned ∡ Ex ∡ k-Space Focused ∡ Ex

𝐹2𝐷 𝐹2𝐷−1

𝑒−𝑗𝑘𝑧𝑧0

Resolution

• Numerical aperture is given as,

where 𝑛 = refractive index of medium

𝜃 = half of angular aperture

• Resolution is given as,

• Theoretically, highest resolution is ~ 𝜆/2

44

𝑁𝐴 = 𝑛 ∗ sin 𝜃

Scanning plane

Source plane

h

d

𝑅 =𝜆

2 ∗ 𝑁𝐴

Ideal Dipole

45

Two dipoles are placed

Dipole 1 at (-100,0,0) mm,

Dipole 2 at (100,0,100) mm

E fields components

Frequency = 10 GHz

Grid spacing = 0.5 mm

Distance = 2.5λ

Resolution ~ 15 mm

Electric

dipoles

Interference pattern on

scanning plane

2.5 λ

Focusing Lens at Different Distances

46

Correct location of dipoles is determinedDipole 2 at

(100,0,100) mm

Dipole 1 at

(-100,0,0) mm

Applications of ESM

47

Measurement Setup:

- The measurement is performed

at 8.2 GHz and at 5 cm away

from DUT.

- Using VNA and open-ended

waveguide used.

5 cm Away from DUT Focused Image

ESM Application of Synthetic Aperture Antenna (SAR) to EMC

- Identification of emission source

- FF estimation

- Total radiated power calculation

Applications of ESM

48

10.3123 10.3124 10.3125 10.3126 10.3127-110

-108

-106

-104

-102

-100

-98

-96

-94

-92

-90

Frequency(GHz)

Radia

ted (

dB

m)

Radiation

Open cover without absorber Scanning height = 7 cm Freq = 10.312509 GHz

Scanned Ex @ 7 cm Focused Ex @ 0 cmNear-Field Hx @ 2 mm

Applications of ESM

49

Without absorbing material With absorbing material

below ASICWith absorbing material

around PHY and below ASIC

With absorbing material

around PHY

TRP from

R-Chamber

Calculated

From ESM

Reduction in TRP 0-1 dB 0-1 dB

TRP from

R-Chamber

Calculated

From ESM

Reduction in TRP 4-5 dB 4-5 dB

Emission Scanning: Conclusion

• EMI scanning is a powerful tool for identifying near-field sources.

• The scanned data can be exported to industry standard format IEC 61967-1-1, and can be imported to full-wave simulation tools.

• Measuring the phase distribution, in addition to magnitude, helps with identifying sources that contribute to far-field using ESM.

• Near-field to far-field transformation and total radiated power estimation are useful applications of phase measurement.

50

51

Thank You!

Questions?

Contact us: amberpi@amberpi.com

www.amberpi.com

References

• Download papers from [Link]

• Application of Emission Source Microscopy Technique to EMI Source Localization above 5 GHz [Link]

• Emission Source Microscopy Technique for EMI Source Localization [Link]

• EMI Mitigation with Lossy Material at 10 GHz [Link]

• Compressed Sensing for SAR-Based Wideband Three-Dimensional Microwave Imaging System Using Non-Uniform Fast Fourier Transform [Link]

• Introduction to Fourier Optics [Link]

• Synthetic Aperture Radar Signal Processing with MATLAB Algorithms [Link]

• Wikipedia: Synthetic Aperture Radar [Link]

• Characterization of Human Metal Model ESD Based on Radiated Susceptibility [Link]

• Modeling Electromagnetic Field Coupling form an ESD Gun to an IC [Link]

• Finding the Root Cause of an ESD Upset Event [Link]

• A Measurement Technique for ESD Current Spreading on A PCB using Near Field Scanning [Link]

• Near Field Probe for Detecting Resonances in EMC Application [Link]

52* http://amberpi.com/library_papers.php