WRS Low Jitter Daugherboard
Project description
The aim of the board is to improve the jitter performance of the 10 MHz and PPS outputs of WR Switch using an external PLL and a new VCTCXO. This project is a spin-off of the general WR low jitter project.
The board needs to be mounted inside an existing WR-S3/18 switch, on top of the Switch Control Board (SCB) and will use the installed 12V power supply of the WRS. It needs a new external 10 MHz input, to be used instead of the current 10 MHz input when configured as Grand Master. The improvements are also effective when configured as boundary switch, thanks to the new VCTCXO.
The proposed board can be installed in any PCB v3.3 and v3.4 versions of the switch.
Key results about the perfomance improvement are published in M. Rizzi, et al. White Rabbit Clock Synchronization: Ultimate Limits on Close-In Phase Noise and Short-Term Stability Due to FPGA Implementation in IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 65, no. 9, pp. 1726-1737, Sept. 2018. doi: 10.1109/TUFFC.2018.2851842
Image of the Low-Jitter Daughterboard
Main Features
Specification
- Modified ADEV at 1s: < 5E-13 (typical 4E-13)
- Modified ADEV at 10s: < 5E-14
- Jitter (10 Hz to 100 kHz): < 2 ps RMS (typical 1.5 ps RMS)
Hardware
- 10 MHz input clock for GrandMaster operation
- wide input power range, from -10 dBm to 20 dBm, sinewave or square
- AD9516-4 low noise PLL for clock synthetization
- Low jitter VCTCXO, 20MHz
- Connor-Winfield DOT050 VCTCXO (DOT050V-020.0M)
- selected as fully protected from airflow
- Option to install another oscillator (14x9mm footprint)
- Abracom ABLNO VCTCXO
- Crystek CCHD-950 VCTCXO
- IQOV-162-3 OCXO (CMOS output)
- Connor-Winfield DOT050 VCTCXO (DOT050V-020.0M)
- 16-bit DAC AD5662 to control the oscillator (used by White Rabbit PTP core)
Project Information
- Hardware: see EDMS (CERN Electronic Document Management System) document EDA-03530-V1-0
- Performance measurements
- Performance of the new board, December 2016
-
ngVLA Memo # 22: Sub-Nanosecond Time Accuracy and Frequency
Distribution,
C. van Tour and J.C.J. Koelemeij, Sept.2017.
- Adding a OCXO to the WRS low-jitter daughterboard to further clean up of phase noise.
- Note that the results with the additional clean-up oscillator require the White Rabbit Grandmaster (GM) to be locked to a sufficiently stable oscillator, such as a rubidium or cesium clock, or a hydrogen maser. The clean-up oscillator will not be able to track the free-running clock of a WR master, which is too unstable. With only the Low jitter daughterboard it will work fine on a free-running GM.
- Frequently Asked Questions
- Gateware and software (download and building)
- Mounting instructions
- Reviews
- Schematics-review 26/10/2016
- Layout-review 21/11/2016
- WRS Low Jitter Daughterboard Report, Seven Solutions, 8 June 2017
Research items
- M. Rizzi et al., White rabbit clock characteristics 2016 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control, and Communication (ISPCS), Stockholm, 2016, pp. 1-6. doi: 10.1109/ISPCS.2016.7579514
- M. Rizzi, et al. White Rabbit Clock Synchronization: Ultimate Limits on Close-In Phase Noise and Short-Term Stability Due to FPGA Implementation in IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 65, no. 9, pp. 1726-1737, Sept. 2018. doi: 10.1109/TUFFC.2018.2851842
Contacts
Commercial products including the LJD hardware
- White Rabbit Switch with LJD prepared hardware
- White Rabbit Switch Fan-less hardware
- White-Rabbit Switch Low Jitter (WRS-LJ) - Seven Solutions in collaboration with the WRITE project.
General question about project
- Mattia Rizzi - CERN
- Erik van der Bij - CERN
Status
| Date | Event |
|---|---|
| 23-10-2016 | Preliminary version of the Schematics ready for review |
| 26-10-2016 | Schematics-review |
| 21-11-2016 | Layout-Review |
| 09-12-2016 | Got the boards |
| 11-12-2016 | Board fully tested |
| 16-12-2016 | Software & Gateware ready |
| 26-12-2016 | Experimental results, mounting and building instructions |
| 20-01-2017 | Two boards shipped to Seven Solutions for evaluation. |
| 24-03-2017 | Seven Solutions measures similar results as measured at CERN. |
| 08-06-2017 | Seven Solutions published WRS Low Jitter Daughterboard Report |
| 25-09-2017 | Two boards will be tested by VTT MIKES Metrology, Time & Frequency in Finland. Results expected by November |
| 27-10-2017 | Measurement results published with addition of extra clean-up OCXO. |
| 06-12-2017 | Measurements by VTT MIKES confirm CERN measurements. These measurements are without an extra clean-up OCXO. |
| 23-11-2018 | Board commercially available and also available in a specifically prepared White Rabbit Switch. |
| 21-04-2020 | A third manufacturer sells White Rabbit Switches with the low-jitter circuitry. |
Mattia Rizzi, Erik van der Bij - 12 June 2023