Download - Round Trip Phase Stability Status
EVLA CDR LO/IF/FO - May 19-20, 2004 1
Round Trip Phase Stability Status
Steven Durand &
Terry Cotter
May 19 ,2004
EVLA CDR LO/IF/FO - May 19-20, 2004 2
Round Trip Phase
• Fiber System• Photographic Tour• Block Diagram • Temperature Effects• Movement Effects
ArrayDistribution
Panel
I FPatch Panel12 WDM per
Fiber
LOPatch Panel
M & CPatch Panel(TX & RX)
74 Fibers 148 Fibers 148 Fibers
Array FO TerminationRoom
North ArmFiber Entrance
(23 Pads,276 Fibers)
East ArmFiber Entrance
(23 Pads,276 Fibers)
West ArmFiber Entrance
(28 Pads,336 Fibers)
Space ReservedE Array Option
(360 Fibers)
EVLA CDR LO/IF/FO - May 19-20, 2004 4
OFS BrightWave Cable
• Double armor loose tube cable
– Corrugated, copolymer coated carbon, steel tape applied longitudinally
• Polyethylene jacket– 1.4 mm outer, 1.2 mm middle, 1.0 mm inner
• Glass/epoxy composite dielectric rod core
EVLA CDR LO/IF/FO - May 19-20, 2004 5
Cable Cross Section
EVLA CDR LO/IF/FO - May 19-20, 2004 6
OFS Matched Cladding Fiber
• Matched cladding single-mode – Nonzero-dispersion optical fiber
• Gel-filled buffer tubes– Installed in a reverse oscillation lay – 12 fibers per tube
EVLA CDR LO/IF/FO - May 19-20, 2004 7
OFS Matched Cladding Specifications @ 1310 nm
• Attenuation coefficient: 0.31-0.35 dB/km• Chromatic dispersion: -9 ps/nm-km• Dispersion slope: 088 ps/nm2-km• Group index of refraction: 1.471• Polarization M dispersion: ≤0.5 ps/(km)1/2 • Rayleigh Backscattering: -49.6 dB• Coefficient of Expansion*: 6 PPM/˚C
* NRAO Estimate
EVLA CDR LO/IF/FO - May 19-20, 2004 8
LO Technical RequirementsBased on the Scientific Goals
after all Round-Trip Corrections
• Short Term: < 0.5 ps RMS per second
• Long Term: < 1.4 ps per 30 minutes ~20 degrees at 40 GHz
• Delta Slope: < 0.2 ps change per minute Over 30 minutes
EVLA CDR LO/IF/FO - May 19-20, 2004 9
Phase Error Allocation
• Front End 0.4 ps per 30 Min• LO Converters 0.6 ps per 30 Min• Fiber System (RTP) 0.4 ps per 30 Min
– RTP measurement accuracy* 0.01 ps– 512 MHz + 128 Hz jitter* 0.1 ps– Fiber induced errors 0.25 ps
*NRAO estimates
EVLA CDR LO/IF/FO - May 19-20, 2004 10
LO Optical System
1310 nm LaserModulator
-6.2 dB6 dBm
Optical Receiver-30 dBm
22 km Fiber
-8.8 dBm
-6.2 dB22 km Fiber
OpticalReceiver-30 dBm
-25 dBm
Connectionsand Splices
Connectionsand Splices
Splitter
5%95%
-23 dBm
-8.8 dBm
-1 dB -14 dB
EVLA CDR LO/IF/FO - May 19-20, 2004 11
Pad Enclosure
EVLA CDR LO/IF/FO - May 19-20, 2004 12
Connectors
EVLA CDR LO/IF/FO - May 19-20, 2004 13
Fiber Umbilical
EVLA CDR LO/IF/FO - May 19-20, 2004 14
Fiber Umbilical
EVLA CDR LO/IF/FO - May 19-20, 2004 15
Fiber Umbilical Antenna Junction Box
EVLA CDR LO/IF/FO - May 19-20, 2004 16
After the Cable Wrap
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Elevation Cable Bend
EVLA CDR LO/IF/FO - May 19-20, 2004 18
Riser
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Old RTP Test Setup
X
OptTx
OptRx
RTP1
512 MHz
RTP1
DC Out
RTP2
DC Out
Mixers
XOptRx
RTP2
Laser
OpticalSplitter
Test designed and operated byDoug Gerrard and Don Haenichen
EVLA CDR LO/IF/FO - May 19-20, 2004 20
RTP Test Hardware
EVLA CDR LO/IF/FO - May 19-20, 2004 21
Analog Mixer as a Phase Detector
EVLA CDR LO/IF/FO - May 19-20, 2004 22
Temperature Effects
• Seasonal–Phase angle changes slowly with ground temperature
• Diurnal–Sunrise and direct Sun issues
EVLA CDR LO/IF/FO - May 19-20, 2004 23
Fiber Enclosure Temperature
(Not Insulated)
EVLA CDR LO/IF/FO - May 19-20, 2004 24
Pad Box Insulation
EVLA CDR LO/IF/FO - May 19-20, 2004 25
Insulated Fiber Box Temperatures
EVLA CDR LO/IF/FO - May 19-20, 2004 26
Temperature Trends
EVLA CDR LO/IF/FO - May 19-20, 2004 27
RTP1 and RTP2
62.0
64.0
66.0
68.0
70.0
72.0
74.0
76.0
78.0
80.0
82.0
84.0
8/29/0312:00
8/29/0318:00
8/30/030:00
8/30/036:00
8/30/0312:00
8/30/0318:00
8/31/030:00
8/31/036:00
8/31/0312:00
8/31/0318:00
9/1/030:00
9/1/036:00
9/1/0312:00
9/1/0318:00
9/2/030:00
9/2/036:00
9/2/0312:00
Date/Time
RT
P1
an
d R
TP
2 P
ha
se
Sh
ift
(de
gre
es
)
-4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Dif
fere
nc
e P
ha
se
Sh
ift
(de
gre
es
)
RTP1 (degrees) RTP2 (degrees) Difference (degrees)
Old 4-Day Stability Test
1° Phase Shift = 5.4 ps
Test Apparatus drift is +/- 0.5 ° per day
~ 0.22 ps per 30 minutes
EVLA CDR LO/IF/FO - May 19-20, 2004 28
Old Test Fixture
• The effects we tried to measure were smaller than the accuracy of the old test fixture.
~ 0.5 degrees (2.7 ps) at 512 MHz
“The Universe is full of Magical things, patiently waiting for our wits to grow sharper”
Eden Phillpots ~ 1900
EVLA CDR LO/IF/FO - May 19-20, 2004 29
New RTP Block Diagram
512 MHzVCO
512 MHzVCXO
ZEROCROSSINGDETECTOR
PLL
512 MHz + 128 Hz
PHASEMONITOR
PLL
MASTER LOGENERATOR
MASTER LO128 Hz TO
DCSSYSTEM
MASTER LO128 Hz 5 MHz
MASTEROFFSETGENERATOR
ROUND TRIPPHASE
MEASUREMENT
MOD LASER
DEMOD
512 MHzDEMOD
512 MHzVCXO
PLLCLEAN
UP
LOREFERENCE
RECEIVER
512 MHz
ANTENNAFO
SYSTEM
CENTRALFOSYSTEM
OPTICALSplitter
EVLA CDR LO/IF/FO - May 19-20, 2004 30
New Round Trip Block Diagram
1310 nm LaserModulator
Optical Receiver-30 dBm
Correlator
PhaseLock Loop
128 HzSignal
512 MHz Signal
Maser
512 MHz Generator128 Hz Generator
5 MHz Generator
512 MHz + 128 HzOffset Generator
Phase Detector
Comparitor
EVLA CDR LO/IF/FO - May 19-20, 2004 31
Diurnal EffectsUsing New Equipment
EVLA CDR LO/IF/FO - May 19-20, 2004 32
Rate of Change of RTPNew Equipment
EVLA CDR LO/IF/FO - May 19-20, 2004 33
Rate of Change of RTP
EVLA CDR LO/IF/FO - May 19-20, 2004 34
Rate of Change of RTP
EVLA CDR LO/IF/FO - May 19-20, 2004 35
Rate of Change of RTP
• Is noise limited - about 0.04° accuracy (0.22 ps)
• Goal: RTP measured and adjusted 10 times/second with an accuracy of 0.01° at 512 MHz
Base SpliceEnclosure
SamplerRACK
LO System
Vertex Room
Lower PedRoom
Upper PedRoom
MCBRACK
ElevationCableBend
AzimuthCable Wrap
12:1 Mux
Vertex SpliceEnclosure
12 SingleMod Fiber
2
2
1
~92ToMIBs Multi
PedestalSplice
Enclosure
12 Single Mode Fibers to Control Building
24Multi
ToMIBs
24Multi
HybridCable
12
EVLA CDR LO/IF/FO - May 19-20, 2004 37
Old Movement Data
EVLA CDR LO/IF/FO - May 19-20, 2004 38
New Movement Data
EVLA CDR LO/IF/FO - May 19-20, 2004 39
New Movement Data
• Test results:
< 0.04 ° shift
@ 512 MHz
• 0.1° =.54 ps
EVLA CDR LO/IF/FO - May 19-20, 2004 40
Rate of Change of RTP
• The Round Trip Phase variation
is less than the noise and/or
accuracy of the measurement
system.
EVLA CDR LO/IF/FO - May 19-20, 2004 41
Conclusion
• The Diurnal Magnitude and rate of change of the phase shift is tolerable:
Estimated to be Less than 0.22 ps / Second
• The Magnitude Effects of the motion is smaller than the accuracy of the present equipment: Less than 0.22 ps
We need to determine the un-compensated effects
EVLA CDR LO/IF/FO - May 19-20, 2004 42
What is Next?
• Obtain a better mixer
• Use an A/D to sample the 128 Hz signal
• FFT to determine the phase
• Take more Measurements
EVLA CDR LO/IF/FO - May 19-20, 2004 43
LO Technical Requirementsafter all Round-Trip Corrections
• Short Term: < 0.5 ps RMS per second
• Long Term: < 1.4 ps per 30 minutes (0.4)
~20 degrees at 40 GHz
• Delta Slope: < 0.2 ps change per minute
Over 30 minutes