Common Common - - mode noise mode noise Impedance Balance Impedance Balance Common Common - - mode output voltage mode output voltage Terry Cobb SYSTIMAX
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
70
80
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