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

EVLA CDR LO/IF/FO - May 19-20, 2004 17

Elevation Cable Bend

EVLA CDR LO/IF/FO - May 19-20, 2004 18

Riser

EVLA CDR LO/IF/FO - May 19-20, 2004 19

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