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Time Calibration Tests
Results using a waveform template
Cross-talk measurements
Stub asymmetry results
Kalle Sulanke
David Hardtke
Bob Stokstad
DOR
DOM
Scope at DOR
Scope at DOM
One-way time = 1/2 round trip time
ONLY IF
Symmetry in pulse generation and transmission
Signal processing same at both ends
Golden Rule of Time Calibration
DORDOR
DOM
DOR - DOM test DOR - DOR test
DOR-DOR has same clock for transmitting and receiving
DOR-DOM AsymmetryTest
DOR - DOR
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100
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400
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1000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Series1Series2
DOR-DOR baseline subtracted
-200.0
-100.0
0.0
100.0
200.0
300.0
400.0
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Series1Series2
V
t
t=V/(V/t)
••
••
•
Clock period 50 ns
Time resolution < 5 ns
Rise time ~400 ns
-> linear algorithm should be OK
-200.0
-100.0
0.0
100.0
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300.0
400.0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Series1Series2
DOR-DOR shifted by one clock tick = 50 ns
391 392-2.3 -2.3-1.3 0.70.7 1.70.7 2.73.7 4.74.7 8.77.7 21.7
21.7 43.7 -22.0 -57.945.7 73.7 -28.0 -51.975.7 109.7 -34.0 -54.0
108.7 148.7 -40.0 -54.8148.7 189.7 -41.0 -48.8 -50.6192.7 230.7 -38.0 -44.7233.7 270.7 -37.0 -46.3272.7 308.7 -36.0 -46.2311.7 338.7342.7 352.7354.7 346.7347.7 319.7318.7 277.7278.7 229.7
V t (ns)
t av
Average asymmetry = -1.3 ns
RMS asymmetry = 1.1 ns
DOR - DOR test
DOR
DOR Card
Av. Asymm RMS asymm
DOM A -1.3 ns 1.1 ns
DOM B -1.2 ns 1.1 ns
DOR Card Test
of Two DOM Configuration
DOM A = 20 cm stub
DOM B = 40 cm cable
DO
R
DO
M A
DO
M B
• •
Runs A_02_04N
B_02_04N
Timing Waveform Analysis• To get roundtrip time, need to analyze waveform:
– Template method -- compare two waveforms and calculate time shift
– Fitting method -- Fit each waveform with function• Failed fit functions -- Error Function, Gaussians, Polynomials• Best fit functions:
€
y =t − t0
a
y > 0 ADC(y) = ped + Ay −3 / 2e−b(y+1/ y )
y <= 0 ADC(y) = pedDOMA_13_188
Waveform Analysis (cont.)Linear fit over limited range, calculate crossing point
with pedestal
Fit range
Round-Trip times using three methods
Waveform comparisonrms = 0.9 ns
Linear fit rms = 3.9 ns
Complicated fitrms = 7.2 ns
Note: absolute scale on x-axis not adjusted properly. OK for residuals, however.
Using measured waveform as template appears promising.
Simple, fast, accurate.
Robust? (likely)
Candidate for use in ice.
Waveform Analysis Summary
NOX_01_A
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Series1Series2
DOR - DOM waveforms
DOR, DOM_B
-50.0
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
400.0
450.0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
Series1
Series2
DORDOM_B
Better symmetry after some component adjustments
DOR - DOM typical results:
Round trip time rms ~ 1 nsfor 3.4 km cable in lab
using template
Boards otherwise "quiet"
No transmission of data in other twisted pair.
Cross-talk studies
•DOR - DOM
•3.4 km Ericsson quad on spool
•Measure round trip rms deviation with and without data xmission at (1 Mbit/s) in other twisted pair
Cross-talk measurement results
round trip residual (rms ns)
DOM A DOM B
Data transmission off 1.1 0.9
to Ericsson quad
Data transmission on 4.4 4.7
in Ericsson quad
Runs X01_A,B NOX01_A,B
Does Cross-talk occur in quad or on DOR card?
Cross-talk measurement results, cont.
round trip residual (rms ns)
DOM A DOM B
Data transmission on 1.5 1.5
to another quad
Data transmission on 4.4 4.7
in Ericsson quad
Runs X01_A,B X03_A,B
=> Most Cross-talk occurs in quad
Cable Cross Talk rms =4.4 ns
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
rms =1.5 ns no cable x-talk
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
4.0
0 1000 2000 3000 4000 5000 6000 7000 8000
Cable cross-talk rms =4.4 nsNo cable cross-talk rms =1.5 ns
Round Trip Time Residuals
Cross-talk, cont.
• Look at pedestal region:
Communications OFF Communications ON
Cross-talk
• Calculate rms of signal in baseline region:
Data transmission in another cable
=> Most cross talk is in cable
Cross-talk, cont.
Try to reduce cross talk by using trapezoidal communications pulse
Result
rms DOM A rms DOM B
4.4 ns 6.0 ns=> No Help
Runs X05_A,B_trap
Timing error budget for clock calibration is 5 ns total -including frequency, offset, asymmetry
DOM clock calibration random systematic quad sumfrequency (sqrt 2 * intrinsic) 2.82clock drift 1offset (1/2 up-down asymmetry, component variations) 4DOM clock calibration subtotal 2.99 4 5.00
Conclude need to shut down data transmission during RAPCAL in order to meet timing requirement, given cross-talk levels in Ericsson quad.
Synchronized shutdown of communications for calibration is now the planned operating mode.
Cable Stub TestsNo Stub Configurations
DOR
DOMa DOMb
15 cm 15 cmterminatedunterminated
3.4 km
cable end
DOR
DOMbDOMa
15 cm 1750 cm3.4 km
1
2
DOR, DOMa, and DOMb are actually one DOR card
Cable Stub TestsStub Configuration
DOR
DOMb
DOMa
130 cm
1750 cm3.4 km
3
Stub test results (preliminary)
DOMa DOMb
asym rms asym rms
15-15 49.9 0.7 49.7 0.5
15-1750 49.1 0.5 49.7 0.5
130-1750 49.7 0.4 49.8 0.7
(NB 1 clock tick = 50 ns. Above absolute asymmetry is due to systematic logic error and is < 1ns.)
DOR card has single clock for all 3 channels
=> Can measure up - down asymmetry
Use centroid of positive portion of pulse
These results suggest that 1.3 m cable stub does not introduce an asymmetry with measurable effect on time calibration.
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