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Time Calibration Tests

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. Golden Rule of Time Calibration. One-way time = 1/2 round trip time ONLY IF

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Time Calibration Tests

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  1. Time Calibration Tests Results using a waveform template Cross-talk measurements Stub asymmetry results Kalle Sulanke David Hardtke Bob Stokstad

  2. DOR DOM

  3. Scope at DOR Scope at DOM

  4. Golden Rule of Time Calibration One-way time = 1/2 round trip time ONLY IF Symmetry in pulse generation and transmission Signal processing same at both ends

  5. DOR DOR DOR-DOM Asymmetry Test DOM DOR - DOM test DOR - DOR test DOR-DOR has same clock for transmitting and receiving

  6. Dt=DV/(dV/dt) V • • • • • t Clock period 50 ns Time resolution < 5 ns -> linear algorithm should be OK Rise time ~400 ns

  7. DOR-DOR shifted by one clock tick = 50 ns

  8. Dt (ns) DV Dt av

  9. DOR - DOR test DOR Average asymmetry = -1.3 ns RMS asymmetry = 1.1 ns

  10. DOR Card DOR Card Test of Two DOM Configuration DOM A = 20 cm stub DOM B = 40 cm cable DOM B DOM A DOR • • Av. Asymm RMS asymm DOM A -1.3 ns 1.1 ns DOM B -1.2 ns 1.1 ns Runs A_02_04N B_02_04N

  11. 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: DOM A_13_188

  12. Waveform Analysis (cont.) Linear fit over limited range, calculate crossing point with pedestal Fit range

  13. Linear fit rms = 3.9 ns Waveform comparison rms = 0.9 ns Complicated fit rms = 7.2 ns Round-Triptimesusing three methods Note: absolute scale on x-axis not adjusted properly. OK for residuals, however.

  14. Waveform Analysis Summary Using measured waveform as template appears promising. Simple, fast, accurate. Robust? (likely) Candidate for use in ice.

  15. DOR - DOM waveforms

  16. Better symmetry after some component adjustments

  17. DOR - DOM typical results:Round trip time rms ~ 1 nsfor 3.4 km cable in labusing template Boards otherwise "quiet" No transmission of data in other twisted pair.

  18. 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

  19. 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

  20. 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

  21. Round Trip Time Residuals No cable cross-talk rms =1.5 ns Cable cross-talk rms =4.4 ns

  22. Communications ON Communications OFF Cross-talk, cont. • Look at pedestal region:

  23. Cross-talk • Calculate rms of signal in baseline region: Data transmission in another cable => Most cross talk is in cable

  24. 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

  25. Timing error budget for clock calibration is 5 ns total -including frequency, offset, asymmetry DOM clock calibration random systematic quad sum frequency (sqrt 2 * intrinsic) 2.82 clock drift 1 offset (1/2 up-down asymmetry, component variations) 4 DOM 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.

  26. cable end unterminated terminated 3.4 km 15 cm 15 cm DOR 1 DOMa DOMb 3.4 km 15 cm 1750 cm DOR 2 DOMa DOMb Cable Stub Tests No Stub Configurations DOR, DOMa, and DOMb are actually one DOR card

  27. 130 cm 3 DOMa DOMb Cable Stub Tests 3.4 km 1750 cm DOR Stub Configuration

  28. DOR card has single clock for all 3 channels => Can measure up - down asymmetry Use centroid of positive portion of pulse Stub test results (preliminary) 1 2 3 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.) These results suggest that 1.3 m cable stub does not introduce an asymmetry with measurable effect on time calibration.

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