Transcript RA Technical Working Group

RA Technical Working Group
on
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 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:
– Week 2:
– Week 3:
2-6 April
14-18 May
18-22 June
• Separate work undertaken by radio users
– Mod / DERA:
– RSGB:
– BBC:
during weeks 2&3
during weeks 2&3
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 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 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 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)
Underground Cable
(Approx. 1 km)
LNEL
Adastral Park
Main Site
Underground Cable
(Approx. 200m)
F
A
E
B
H
D
Hut 2
Overhead Dropwires
NT
4 Acre Test Site
C
Wireline EMC
Test Facility
= Poles
Hut 89
Not to be used outside the RA TWG on VDSL without written permission from RA and BT
7: 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)
Net Insertion Loss (Routes A-F)
0
-5
Level (dB)
-10
-15
-20
-25
-30
-35
-40
100.0E+3
1.0E+6
10.0E+6
Frequency (Hz)
100.0E+6
Route DCLR (W)
A1
40.6
A2
40.9
B1
40.8
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
Not to be used outside the RA TWG on VDSL without written permission from RA and BT
9: Line Balance Characteristic
(BT)
Cable Balance (Routes A-F)
0
-20
Level (dB)
-40
-60
-80
-100
-120
100.0E+3
1.0E+6
10.0E+6
100.0E+6
Frequency (Hz)
Not to be used outside the RA TWG on VDSL without written permission from RA and 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)
Relative PSD of 4-Band VDSL Modem
0
-10
1/2 System
Clock
(12.98MHz)
-20
Level (dB)
-30
Out of band
interference
-40
-50
System Clock
(25.96MHz)
-60
-70
-80
-90
000.0E+0
5.0E+6
10.0E+6
15.0E+6
20.0E+6
25.0E+6
30.0E+6
Frequency (Hz)
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
• 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)
New EMC Test Facility
(4-Acre Site)
N
Perimet er Fen ce
*
F -1
A- 1
S6
Du ct ( P42)
F -2
Ro
ut e
S1
ut e
Ro
F
A- 2
A
3.5m
E-1
Ro ut e E
S5
BT 18
B- 1
Ro ut e B
S2
H
B- 2
E-2
ut e
Ro
D
Ro
ut
eC
D- 1
C- 1
S4
S3
C- 2
D- 2
Pol e C
41m
KEY
*
Cable Joi nt
Pol e
50 pai r 0. 5mm gauge cable
20 pai r 0. 5mm gauge cable
Joi nt Box
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)
Dropwire
Pole
Downlead
3m
Measurement
Antenna
1m
1m
Ground
Not to be used outside the RA TWG on VDSL without written permission from RA and BT
15: 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)
VDSL Em issions m easured at 1 m etre spacing from the 'custom er end' dropw ire
Equivalent E field (dBuV/m in 9 kHz - Peak)
50
45
40
1.65 MHz
35
3.10 MHz
30
4.03 MHz
4.83 MHz
25
6.55 MHz
20
6.98 MHz
9.59 MHz
15
10.50 MHz
10
5
0
A1
A2
B1
B2
C1
C2
D1
D2
E1
E2
F1
F2
Test Route Num bers (nom inally identical 260 m etre circuits)
Not to be used outside the RA TWG on VDSL without written permission from RA and BT
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)
Route E VDSL Em issions
Measured at 1 m etre spacing from the 'custom er end 'of a 260 m etre circuit
Equivalent E field (dBuV/m in 9 kHz - Peak)
100
90
80
70
60
50
40
30
20
1000
3000
5000
7000
9000
11000
Frequency (kHz)
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)
Route D1 VDSL em issions -- Effect of a Split Pair
Measured at 1 m etre spacing from the 'custom er end' of a 260 m etre cicuit
100
Equivalent E field(dBuV/m in 9 kHzPeak)
90
80
70
60
50
40
30
20
1000
3000
5000
7000
9000
11000
Frequency (MHz)
VDSL on D1
VDSL Upstream Band
VDSL on Split Pair
Ambient
VDSL Downstream Band
Not to be used outside the RA TWG on VDSL without written permission from RA and BT
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 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
Dropwire
Pole
Downlead
3m
Measurement
Antenna
1m
1m
1m
Ground
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
Freq MHz
1.65
3.1
4.03
4.85
6.55
6.98
9.64
10.5
1 to 3 metre
-9.8 dB
-6.7
-20.3
-3
-14.3
-15.4
-9.6
-8
3 to 10 metres
1 to 10 metres
-2.7 dB
-10.7
2.2
-1.5
-6.9
-5.7
-1.2
-11.4
-12.5 dB
-17.4
-18.1
-4.5
-21.2
-21.1
-10.8
-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 Dropwire
Dropwire (Route D)
1m
3m
Measurement
Antenna
Pole H
Pole D
Ground
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
Overhead Dropwires
F
A
H
E
B
Route D
D
10m
C
Balun
Dipole Antenna
Coaxial Cable
= Poles
Receiver
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
1m to 3 m loop
3m loop to 10m dipole
1m loop to 10m dipole
D1
D1
Freq. MHz
D1
D2
(dB)
D2
(dB)
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 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 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 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 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 Measurements
– Broadband Guassian white noise generatorwith 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)
Route D2 Em issions - To show current nodes and antinodes
Signal - Broadband noise w ith a launch pow er of -45 dBm / Hz - NOT VDSL
Measured at 1 m etre spacing from the 'custom er end ' of the Route D2 260 m etre circuit
Equivalent E field (dBuV/m in 9 kHz - Peak)
100
All 12 circuits at 260 metres Ground on D2 Black
90
D1 extended to 300 metres
Plus E1 extended
80
70
60
50
40
30
20
1000
3000
5000
7000
9000 11000 13000 15000 17000 19000 21000 23000 25000 27000 29000
Frequency (kHz)
Not to be used outside the RA TWG on VDSL without written permission from RA and BT
33: 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 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)
Route B1 Emissions -- To Show Field Strength Regression
Measured w ith -25 dBm / Hz launch pow er - NOT VDSL
100
Equivalent E field (dBuV/m in 9 kHzPeak )
90
80
70
60
50
40
30
20
1000
3000
5000
7000
9000 11000 13000 15000 17000 19000 21000 23000 25000 27000 29000
Frequency in kHz
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 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’
• 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
VDSL Emissions 'w ithin a user premises'
Measured at 1 metre from dedicated Cat 5 w iring and 3 metres from VDSL splitter
Equivalent E Field (dBuV/m in 9 kHz - Peak)
100
90
80
70
60
50
40
30
20
1000
3000
5000
7000
9000
11000
Frequency in kHz
VDSL Normal Operation
VDSL Downstream Band
Ambient
VDSL Faulty Operation (split pair dropwire)
VDSL Upstream Band
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)
VDSL emissions inside a 'user premises' w ith No VDSL Splitter
Measured a 1 metre spacing from internal telephone extension w iring
Equivalent E Field (dBuV/m in 9 kHz - Peak)
100
90
80
70
60
50
40
30
20
1000
3000
5000
7000
9000
11000
Frequency in kHz
ARGOS 'self install' telephone wiring
BT CW1308 with split pair dropwire
Ambient
BT CW1308 telephone wiring
VDSL Downstream Band
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 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
Not to be used outside the RA TWG on VDSL without written permission from RA and BT