Not to be used outside the RA TWG on VDSL without written permission from RA and BT

RA Technical Working Groupon

VDSL & PLT Compatibility With Radio Services

RA Technical Working Groupon

VDSL & PLT Compatibility With Radio Services

VDSL Emission Measurement Programme

Status Report to the TWG

3rd July 2001

Colin Wooff (RA3/RTCG)

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

2: The RA VDSL Measurement Programme2: The RA VDSL Measurement Programme

• Test schedule agreed by TWG on 30th March• Conducted by RTCG using BT test facilities• Planned in three separate phases• Each phase lasted one week

– Week 1: 2-6 April – Week 2: 14-18 May– Week 3: 18-22 June

• Separate work undertaken by radio users– Mod / DERA: during weeks 2&3– RSGB: during weeks 2&3– BBC: during week 3

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

3: The RA VDSL Measurement Programme3: The RA VDSL Measurement Programme

Today’s presentation:

– Programme objectives

– Measurement objectives

– Test procedures

– Swept measurements

– Results

– Observations

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

4: The RA VDSL Measurement Programme4: The RA VDSL Measurement Programme

Overall programme objectives (TWG(01)06)

– Discover range of radiated emission levels

– Assess likely effects on nearby radio systems

– Provide data to predict cumulative effects

– Inform UK input to international fora

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

5: The RA VDSL Measurement Programme5: The RA VDSL Measurement Programme

Measurement objectives:

– Characterize lines ( BT)– Characterize VDSL modems (BT)– Determine radiated emission levels– Correlate line balance with emission

levels– Assess factors that may effect emission

levels– Measure emission level attenuation

with distance

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

6: BT Adastral Park - 4 Acre Test Site

(BT)

6: BT Adastral Park - 4 Acre Test Site

(BT)

Adastral ParkM ain S ite

LNEL

W ireline EM CTest Facility

Hut 2

4 Acre Test S ite

Underground Cable(Approx. 1 km )

Underground Cable(Approx. 200m )

O verhead Dropwires

Hut 89

NT

A

B

DC

F

HE

= Poles

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

7: The RA VDSL Measurement Programme7: The RA VDSL Measurement Programme

Line characteristics (supplied by BT)

– D.C. Loop resistance

– Insertion loss

– Balance

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

8: Line Insertion Loss & Loop Resistance (BT)

8: Line Insertion Loss & Loop Resistance (BT)

Route DCLR (

A1 40.6

A2 40.9

B1

B2 40.7

C1 41.1

C2 41.4

D1 40.6

D2 41

E1 40.8

E2 40.9

F1 41.1

F2 41.1

Net Insertion Loss (Routes A-F)

-40

-35

-30

-25

-20

-15

-10

-5

0

100.0E+3 1.0E+6 10.0E+6 100.0E+6

Frequency (Hz)

Le

ve

l (d

B)

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

9: Line Balance Characteristic (BT)9: Line Balance Characteristic (BT)

Cable Balance (Routes A-F)

-120

-100

-80

-60

-40

-20

0

100.0E+3 1.0E+6 10.0E+6 100.0E+6

Frequency (Hz)

Le

ve

l (d

B)

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

10: Modem Specification (BT)10: Modem Specification (BT)

• Highly integrated prototype • Built to ETSI TS101 270-2 • Conforms to 998 VDSL plan• Broadband SCM • 25 M bit/s downstream • 8 M bit/s upstream • Max PSD: -60dbm / Hz• Power back off facility

(upstream)

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

11: Modem Output Spectrum (BT)11: Modem Output Spectrum (BT)

Relative PSD of 4-Band VDSL Modem

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

000.0E+0 5.0E+6 10.0E+6 15.0E+6 20.0E+6 25.0E+6 30.0E+6

Frequency (Hz)

Le

ve

l (d

B)

System Clock (25.96MHz)

1/2 System Clock (12.98MHz)

Out of band interference

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

12: Week 1 Measurements Spot Frequency Radiated Emissions

12: Week 1 Measurements Spot Frequency Radiated Emissions

• Measurements made on all 6 available lines

• Each line has 2 wire pairs - 12 circuits in total

• All 12 circuits nominally 260 metres long between the downstream and upstream VDSL modems

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

13: Measurement Locations - Plan View (BT)

13: Measurement Locations - Plan View (BT)

New EMC Test Facility(4-Acre Site)

Perimeter Fence

KEY

Pole

20 pair 0.5mm gauge cable

Joint Box

N

S1

S2

S3S4

S5

S6

Route BRoute E

Duct (P42)

H

A-1

A-2

B-1

B-2

C-1

C-2D-2

D-1

E-2

E-1

F-2

F-1

50 pair 0.5mm gauge cable

*

Pole C * Cable Joint

BT 18

3.5m

41m

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

14: Loop Antenna Position - ‘Customer End’ (Near the NTP and Modem)

14: Loop Antenna Position - ‘Customer End’ (Near the NTP and Modem)

1 m

Dropwire

Measurem entAntenna

G round

1 m

3 m

Downlead

Pole

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

15: Test Equipment Configuration Spot Frequency Measurements15: Test Equipment Configuration Spot Frequency Measurements

U of H tuned loop antenna - used to achieve a lower measuring system noise floor

1 metre spacing from dropwire

CISPR receiver - 9kHz BW - peak detector Two ‘quiet’ test frequencies within each

of the 4 VDSL deployment bands

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

16: VDSL Emission Levels at 1 m Spacing (See Handout for More Detail)

16: VDSL Emission Levels at 1 m Spacing (See Handout for More Detail)

VDSL Emissions measured at 1 metre spacing from the 'customer end' dropwire

0

5

10

15

20

25

30

35

40

45

50

A1 A2 B1 B2 C1 C2 D1 D2 E1 E2 F1 F2

Test Route Numbers (nominally identical 260 metre circuits)

Eq

uiv

alen

t E

fie

ld (

dB

uV

/m in

9 k

Hz

- P

eak)

1.65 MHz

3.10 MHz

4.03 MHz

4.83 MHz

6.55 MHz

6.98 MHz

9.59 MHz

10.50 MHz

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

17: Observations Spot Frequency Emission Measurements

17: Observations Spot Frequency Emission Measurements

• All emissions were above measuring system noise floor

• Larger than expected variation between emissions from the 2 pairs in a single dropwire

• Little apparent correlation between emissions from different routes

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

18: Swept Measurements - VDSL Emissions (Normal Operation)

18: Swept Measurements - VDSL Emissions (Normal Operation)

Route E VDSL EmissionsMeasured at 1 metre spacing from the 'customer end 'of a 260 metre circuit

20

30

40

50

60

70

80

90

100

1000 3000 5000 7000 9000 11000

Frequency (kHz)

Eq

uiv

alen

t E

fie

ld (

dB

uV

/m in

9 k

Hz

- P

eak)

VDSL on E1 VDSL on E2 VDSL Downstream Band VDSL Upstream Band Ambient

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

19: VDSL Emissions - Split Pair Drop Wire (FAULT Condition)

19: VDSL Emissions - Split Pair Drop Wire (FAULT Condition)

Route D1 VDSL emissions -- Effect of a Split PairMeasured at 1 metre spacing from the 'customer end' of a 260 metre cicuit

20

30

40

50

60

70

80

90

100

1000 3000 5000 7000 9000 11000

Frequency (MHz)

Eq

uiv

alen

t E

fie

ld(d

Bu

V/m

in 9

kH

z-P

eak)

VDSL on D1 VDSL on Split Pair VDSL Downstream BandVDSL Upstream Band Ambient

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

20: Observations: Swept Frequency Emission Measurements

20: Observations: Swept Frequency Emission Measurements

• The significant variability in the VDSL frequency v emission profile is easily seen

• High measuring system noise floor using this method with a standard CISPR loop antenna would prevent a complete analysis of the 1, 3 and 10 metre VDSL field strength attenuation

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

21: Field Attenuation With Distance Spot Frequency Measurements21: Field Attenuation With Distance Spot Frequency Measurements

• Agreed value needed:• To correct emission measurements

made at one distance to limits specified at another distance

• To assess potential interference effects at distances other than those used for emission measurements

• To provide data for cumulative emission studies

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

22: 1 to 3 & 10 Metre Field Attenuation Loop Antenna - Vertical Dropwire

22: 1 to 3 & 10 Metre Field Attenuation Loop Antenna - Vertical Dropwire

1 m

Dropwire

Measurem entAntenna

G round

1 m 1 m

3 m

Downlead

Pole

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

23: 1 to 3 / 10 Metre Field Attenuation Loop Antenna - Vertical Dropwire

23: 1 to 3 / 10 Metre Field Attenuation Loop Antenna - Vertical Dropwire

Freq MHz 1 to 3 metre 3 to 10 metres 1 to 10 metres

1.65 -9.8 dB -2.7 dB -12.5 dB3.1 -6.7 -10.7 -17.4

4.03 -20.3 2.2 -18.14.85 -3 -1.5 -4.56.55 -14.3 -6.9 -21.26.98 -15.4 -5.7 -21.19.64 -9.6 -1.2 -10.810.5 -8 -11.4 -19.4

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

24: 1 to 3 Metre Field Attenuation Loop Antenna - Horizontal Dropwire24: 1 to 3 Metre Field Attenuation Loop Antenna - Horizontal Dropwire

Dropwire (Route D)

Measurem entAntenna

G round

1 m

3 m

Pole HPole D

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

25: 1 & 3 Metre Loop to 10m Dipole Attenuation Measurements - Horizontal Dropwire

25: 1 & 3 Metre Loop to 10m Dipole Attenuation Measurements - Horizontal Dropwire

O verhead Dropwires A

B

D C

F

H

E

= Poles

Balun

Coaxial Cable

Route D

Receiver

D ipole Antenna

10m

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

26: 1 & 3 Metre Loop to 10m Dipole Relative Field From Horizontal Dropwire

26: 1 & 3 Metre Loop to 10m Dipole Relative Field From Horizontal Dropwire

1m to 3 m loop 3m loop to 10m dipole 1m loop to 10m dipoleFreq. MHz

D1 D2 (dB) D1 D2 (dB) D1 D2 (dB)

3.65 -7 1 -6.39 -16.39 -13.39 -15.39

7.05 -8 -5.4 -23.24 -20.84 -31.24 -26.24

10.125 -14 -6 -16.48 -19.48 -30.48 -25.48

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

27: Observations - Field Attenuation Results27: Observations - Field Attenuation Results• Large variations at different frequencies

• 3 m loop to 10 m dipole values larger than predicted by the 20 log d1/d2 formula

• Close-in loop measurements seem unlikely to be suitable for predicting far field effects.

• Spot frequency measurement do not provide sufficient data to facilitate proper analysis

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

28: Other Findings28: Other Findings

No effect on VDSL emission levels observed when the POTS circuit was disconnected at both ends of the line

No effect on VDSL emission levels observed due to the simultaneous operation of the POTS circuit

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

29: Conclusions After First Week29: Conclusions After First Week

• Need to explain the variability of VDSL emission results before declaring them as valid

• Statistical analysis based on a large number of swept measurements look more promising

• High power broadband noise signal with flat PSD necessary to measure field attenuation with balanced lines

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

30: Week 2 Measurements High Power Broadband Tests30: Week 2 Measurements High Power Broadband Tests

• To examine resonances in VDSL lines without undue intrusion from ambient signals

• To facilitate the analysis of field attenuation with distance

• To allow user group assessments at larger separation distances where emissions can be scaled down to VDSL PSD levels

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

31: High Power Broadband Tests Equipment for Swept Measurements31: High Power Broadband Tests Equipment for Swept Measurements

– Broadband Guassian white noise generator- with high power amplifier - giving a launch PSD of up to - 25 dBm/Hz

– High power balun for connection to lines– High power balanced load resistor

– CISPR magnetic loop antenna – CISPR measuring receiver with fast

scanning and data storage facility

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

32: Line Resonance and Parasitic Effects High Power Broadband Source - NOT VDSL (Unbalanced to Increase Common Mode Current)

32: Line Resonance and Parasitic Effects High Power Broadband Source - NOT VDSL (Unbalanced to Increase Common Mode Current) Route D2 Emissions - To show current nodes and antinodes

Signal - Broadband noise w ith a launch power of -45 dBm / Hz - NOT VDSLMeasured at 1 metre spacing from the 'customer end ' of the Route D2 260 metre circuit

20

30

40

50

60

70

80

90

100

1000 3000 5000 7000 9000 11000 13000 15000 17000 19000 21000 23000 25000 27000 29000

Frequency (kHz)

Eq

uiv

alen

t E

fie

ld (

dB

uV

/m in

9 k

Hz

- P

eak)

All 12 circuits at 260 metres Ground on D2 Black

D1 extended to 300 metres

Plus E1 extended

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

33: Basic Observations on Line Resonances33: Basic Observations on Line Resonances

• Current nodes can be expected at half wavelength intervals related to the electrical length of the line in respect of the common mode standing wave

• Parasitic effects can be observed at the BT site by varying the lengths of the nominally identical circuits which are closely coupled within the 20 pair underground feed cable

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

34: Consequences of the Resonance Effects34: Consequences of the Resonance Effects

• Common mode terminations, line parasitic and proximity effects may all conspire to vary the position of the current nodes in a totally unpredictable way

• Single frequency magnetic field emission measurements are likely to be misleading in these circumstances

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

35: Field Attenuation With Distance High Power Broadband Source - NOT VDSL (Balanced Line)

35: Field Attenuation With Distance High Power Broadband Source - NOT VDSL (Balanced Line)

Route B1 Emissions -- To Show Field Strength Regression Measured w ith -25 dBm / Hz launch power - NOT VDSL

20

30

40

50

60

70

80

90

100

1000 3000 5000 7000 9000 11000 13000 15000 17000 19000 21000 23000 25000 27000 29000

Frequency in kHz

Eq

uiv

alen

t E

fie

ld (

dB

uV

/m in

9 k

Hz-

Pea

k )

1 metre 3 metres 10 metres

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

36: Observations - Field Attenuation36: Observations - Field Attenuation

• Line resonance effects demonstrate the difficulty of achieving consistent results based on this measurement technique

• It can be seen that current nodes vary in frequency at the 3 measuring distances which may be due to the proximity effect of the loop or inherent when using a directional antenna near a distributed source radiator

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

37: Week 3 - VDSL Emissions ‘in the Home’37: Week 3 - VDSL Emissions ‘in the Home’

• A fundamental issue in relation to HF broadcast reception

• Important to understand how installation variables may affect emission levels

• Necessary to know by how much the most common installation FAULT will increase emission levels

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

38: User Premises VDSL Emissions BT ‘Classic’ Installation - With Splitter

38: User Premises VDSL Emissions BT ‘Classic’ Installation - With Splitter

VDSL Emissions 'w ithin a user premises'Measured at 1 metre from dedicated Cat 5 wiring and 3 metres from VDSL splitter

20

30

40

50

60

70

80

90

100

1000 3000 5000 7000 9000 11000

Frequency in kHz

Eq

uiv

alen

t E

Fie

ld (

dB

uV

/m in

9 k

Hz

- P

eak)

VDSL Normal Operation VDSL Faulty Operation (split pair dropwire)VDSL Downstream Band VDSL Upstream BandAmbient

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

39: User Premises VDSL Emissions ‘Self Install’ Installation - No Splitter(BT is not currently contemplating self-install VDSL)

39: User Premises VDSL Emissions ‘Self Install’ Installation - No Splitter(BT is not currently contemplating self-install VDSL)

VDSL emissions inside a 'user premises' w ith No VDSL SplitterMeasured a 1 metre spacing from internal telephone extension wiring

20

30

40

50

60

70

80

90

100

1000 3000 5000 7000 9000 11000

Frequency in kHz

Eq

uiv

alen

t E

Fie

ld (

dB

uV

/m in

9 k

Hz

- P

eak)

ARGOS 'self install' telephone wiring BT CW1308 telephone wiringBT CW1308 with split pair dropwire VDSL Downstream BandAmbient VDSL Upstream Band

Not to be used outside the RA TWG on VDSL without written permission from RA and BT

40: Initial Conclusions on VDSL Emissions40: Initial Conclusions on VDSL Emissions

• VDSL emission levels ‘in the home’ with a splitter and CAT 5 wiring installed are similar to those measured on the incoming dropwire outside

• Self install VDSL without a splitter will show significantly higher emissions

• The ‘split pair’ fault under which VDSL may still operate normally gives the highest emission levels