®04/29/2002

CISPR 22, Amendment 1Ferrite Clamps

Ghery S. Pettit, NCEIntel Corporation

Co

rpor

ate

Pro

duc

t Reg

ula

tion

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Topics

• OATS Qualification• Amendment 1, CISPR 22:1997• Problems

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Typical OATS Facility

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OATS Qualification

• Normalized Site Attenuation– Transmit antenna on turntable center– Receiver antenna on tower– +/- 4 dB and you pass

• Nothing said about– Power distribution to EUT– Cables to remotely located peripheral devices

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Long Wire End Fed Antennas

• Random length wire• Transmitter at one end• Far end – who knows where?

xmtr

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Look Familiar?

• EUT = Transmitter• Power cord = Antenna• Power feed (from who knows where?) =

End support and termination

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Common Unknowns

• Wire length (resonant frequencies)• Wire termination (load)• Wire orientation (once it leaves the

turntable)

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How To Standardize?

• Standard wire length and layout– Redesign labs?

• Major world-wide expense• Not likely to be accepted

– LISNs at power plugs?• What about labs where power is under the table?• What about labs where there isn’t room?

• Solution is to decouple all but the cable in the test area.

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CISPR 22, 3rd Edition, Amendment 1(EN 55022:1998, Amendment 1)

• Adds ferrite clamps – all cables leaving the measurement area for

table top EUTs – at the surface of the turntable– 1 cable per clamp

• Published in August 2000.• Has been adopted by Israel and the EU.• Required in EU by 1 August 2003.

– Israel now, others later

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Ferrite Clamps

Table top products only

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Ferrite Clamp Definition

• The clamp shall– Provide at least 15 dB of loss in a 50 ohm system– 30 MHz to 1000 MHz

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Does It Work?

• Tests performed by Intel and Hewlett Packard in early 2000 to aid in the US vote on the amendment

• Comb generator to power cord via a CDN• Radiated emissions measured every 5 MHz from

30 MHz to 200 MHz• 4 lab configurations with a single clamp

– Schaffner INA 726 Isolation Clamp

• 2 lab configurations with 3 different clamps– Schaffner INA 726 Isolation Clamp– MDS 21 Absorbing Clamp– Fischer Custom Communications F-203I-23mm EM

Clamp

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Test Setup – No Ferrite Clamp

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Test Setup – With Ferrite Clamp

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4 Sites – No Ferrite

Measured Signals - No Ferrite

15

20

25

30

35

40

45

50

30 40 50 60 70 80 90 100

110

120

130

140

150

160

170

180

190

200

Frequency (MHz)

Sig

nal

(d

Bu

V/m

)

HP - NEMA Outlet HP - LISN Outlet Intel DuPont Intel Oregon

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4 Sites – With Ferrite

Measured Signals - Ferrite on Cord

15

20

25

30

35

40

45

30 40 50 60 70 80 90 100

110

120

130

140

150

160

170

180

190

200

Frequency (MHz)

Sig

nal

(d

Bu

V/m

)

HP - NEMA Outlet HP - LISN Outlet Intel DuPont Intel Oregon

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4 Sites - Summary

Effect of Adding Ferrite Clamp

0

5

10

15

20

2530 40 50 60 70 80 90 10

0

110

120

130

140

150

160

170

180

190

200

Frequency (MHz)

Sp

read

(d

B)

Data Spread - No Ferrite Clamp Data Spread - Ferrite Clamp

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3 Clamps – Two Power Feeds

Clamp Comparison

20

25

30

35

40

45

30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

Frequency (MHz)

Sig

nal

Lev

el (

dB

uV

/m)

NEMA Outlet - Schaffner INA 726 NEMA Outlet - MDS 21

NEMA Outlet - FCC Clamp LISN - Schaffner INA 726

LISN - MDS 21 LISN - FCC Clamp

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Two Power Feeds – No Clamp

HP Chamber Results - No Ferrite

15

20

25

30

35

40

45

30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

Frequency (MHz)

Sig

nal

Lev

el

(dB

uV

/m)

NEMA Outlet LISN Outlet

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Two Power Feeds – INA 726

Schaffner INA 726

20

25

30

35

40

45

30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

Frequency (MHz)

Sig

nal

Lev

el

(dB

uV

/m)

NEMA Outlet LISN Outlet

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Two Power Feeds – MDS 21

MDS 21

20

25

30

35

40

45

30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

Frequency (MHz)

Sig

nal

Lev

el

(dB

uV

/m)

NEMA Outlet LISN Outlet

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Two Power Feeds – FCC EM Clamp

Fischer Custom Communications Clamp

20

25

30

35

40

45

30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

Frequency (MHz)

Sig

nal

Lev

el

(dB

uV

/m)

NEMA Outlet LISN Outlet

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Initial Conclusion

• Clamps improve repeatability between labs• Clamps improve repeatability between different

types of power feeds in the same lab• Different clamps converge to different solutions

– Why?

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One More Clamp Characteristic

• Need to specify the input impedance for a wire passing through the clamp

• Measurements show each clamp utilized– Meets the 15 dB loss requirement from 30 MHz to 1000

MHz– Has a different impedance characteristic

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INA 726 Input Impedance

Schaffner INA 726 Input Impedance

0

100

200

300

400

500

600

700

800

900

1000

0 100 200 300 400 500 600 700 800 900 1000

Frequency (MHz)

Ohm

s

Open Shorted

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MDS 21 Input Impedance

MDS 21 Input Impedance

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 100 200 300 400 500 600 700 800 900 1000

Frequency (MHz)

Ohm

s

Open Shorted

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FCC EM Clamp Input Impedance

Fischer F-203I-23mm Clamp Input Impedance

0100

200300

400500600

700800

9001000

0 100 200 300 400 500 600 700 800 900 1000

Frequency (MHz)

Ohm

s

Open Shorted

28®04/29/2002

Where Do We Go From Here?

• Problem #1– CISPR 22 uses ferrite clamps on cables– ANSI C63.4 does not

• Problem #2– CISPR 22 does not adequately define the clamps– What should the input impedance to the wire through the

clamp be?