CommonCommon--mode noisemode noiseImpedance Balance Impedance Balance

CommonCommon--mode output voltagemode output voltage

Terry CobbSYSTIMAX

May 2005 IEEE 802.3an 10GBASE-T

CommonCommon--mode noisemode noise

• Generate a RF signal equal to the signal defined in IEC 61000 for an electromagnetic field immunity test and measure the common-mode current.

• This test was not conducted in a chamber and the field was not calibrated, additional verification is required.

• Determine a clamp input voltage that would create a similar common-mode current.

May 2005 IEEE 802.3an 10GBASE-T

RF SignalRF Signal

Modulated RF signal 80% AM, 5.1v p-p

For the clamp an unmodulated RF signal is used.

May 2005 IEEE 802.3an 10GBASE-T

Antenna Test Set UpAntenna Test Set Up

Create a common-mode current with RF signal

50ΩΩΩΩ 50ΩΩΩΩ50ΩΩΩΩ

Termination

Current Probe

May 2005 IEEE 802.3an 10GBASE-T

Clamp Test Set UpClamp Test Set Up

Create a similar common-mode current using the clamp

50ΩΩΩΩ 50ΩΩΩΩ50ΩΩΩΩ

Termination

Current Probe

May 2005 IEEE 802.3an 10GBASE-T

0

20

40

60

80

100

120

30 130 230 330 430 530 630 730 830 930

Frequency (MHz)

Cu

rren

t (d

Bu

I)

Input1 pair

CommonCommon--mode current mode current Using a single twisted pairUsing a single twisted pair

Clamp does produce a fairly constant common-mode current for single twisted pair

May 2005 IEEE 802.3an 10GBASE-T

010

20

304050

60

708090

30 130 230 330 430 530 630 730 830 930

Frequency (MHz)

Cur

rent

(dB

uI)

w /Antennaw/Clamp

Comparison of commonComparison of common--mode current mode current Measuring one pair in a four pair cableMeasuring one pair in a four pair cable

Clamp Input = + 6 dBm

May 2005 IEEE 802.3an 10GBASE-T

CISPR 24 Annex C (LAN) Requirement CISPR 24 Annex C (LAN) Requirement for Radiated Immunityfor Radiated Immunity

• Performance criterion A – No errors.

• Performance criterion B – Degraded transmission but self-recoverable.

• Performance criterion C – Degraded transmission but self-recoverable or can

be restored after the test by the operator.

The following are the accepted performance criteria:

May 2005 IEEE 802.3an 10GBASE-T

-90-80-70-60

-50-40-30-20-10

0

30 130 230 330 430 530 630 730 830 930

Frequency (MHz)

Imp

edan

ce B

alan

ce (

dB)

SCD22Old Limit

Impedance BalanceImpedance Balance

SCD22 = SCD21/SDD21

May 2005 IEEE 802.3an 10GBASE-T

-100

-80

-60

-40

-20

0

30 130 230 330 430 530 630 730 830 930

Frequency (MHz)

Impe

danc

e Ba

lanc

e (d

B)

A_SCD22B_SCD22C_SCD22D_SCD22New Limit

Proposed Impedance BalanceProposed Impedance Balance

50 30 MHz ≤ ƒƒƒƒ < 100 MHz 50 + 32 x ((ƒƒƒƒ-100)/1000) 100 MHz ≤ ƒƒƒƒ ≤ 1000 MHz

Note: There was one channel that was 3 dB (at 1000MHz) worse than the others.

May 2005 IEEE 802.3an 10GBASE-T

-50-45-40-35-30-25-20-15-10-50

30 130 230 330 430 530 630 730 830 930

Frequency (MHz)

Co

mm

on

-mo

de

ou

tpu

t vo

ltag

e (d

Bm

_50o

hm

s)

Vcom

CommonCommon--mode output voltagemode output voltage

Common-mode output voltage is approximately the Impedance Balance (SCD22) x VDD (5.2 dBm_100ohms) x PSDmask

- 32.8 dBm at 1000MHz

May 2005 IEEE 802.3an 10GBASE-T

Purpose of TestPurpose of Test

Impedance Balance Test

Common-mode Output Voltage Test

May 2005 IEEE 802.3an 10GBASE-T

0

10

20

30

40

50

60

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200 300 400 500 600 700 800 900 1000Frequency (MHz)

dBuV

/m

Background50mv_p-p15mv_p-pClass_A_3m_Limit

CommonCommon--mode Output Voltage Levelmode Output Voltage Level

Tested at: 210 MHz, 500 MHz, 750 MHz, 975 MHz

50ΩΩΩΩ 50ΩΩΩΩ

Termination

Signal Generator

May 2005 IEEE 802.3an 10GBASE-T

0

10

20

30

40

50

60

70

200 300 400 500 600 700 800 900 1000

Frequency (MHz)

dBuV

/m

50mv_p-p15mv_p-pClass_A_3m_Limit

CommonCommon--mode Output Voltage Level mode Output Voltage Level (without background noise)(without background noise)

50 mv p-p Fails

15 mv p-p Fails