Hi The gotcha with the papers is the "RMS" measure of accuracy. A more conventional counter would call 30 ps RMS, 90 ps accuracy...
Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Attila Kinali Sent: Tuesday, December 06, 2011 5:05 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Help with TCXO On Tue, 6 Dec 2011 21:47:24 +0100 Azelio Boriani <[email protected]> wrote: > I have read about the two main delay line techniques: the vernier delay > line and the tapped delay line. These require a sort of on-the-fly > calibration virtually for every sample you get because of the temperature > and power supply dependency of the delay itself. Presently my > time-to-digital converter has a 2.5nS resolution made only by counters, > based on a 100MHz clock and on the capabilities of the Digital Clock > Manager in the Spartan3 XC3S50 FPGA. In your opinion what resolution can I > get from a Spartan3 (without any calibration) using delay lines? I have to > learn how to manage delay lines and how to direct their placement for > time-nut purposes. Google for [1]. Wu et al reports that he was able to get to <60ps RMS uncalibrated on a Cyclone II chip (which is quite old and slow). Calibrated it was in the range of 10-25ps RMS (depending on the exact architecture). In [2] Qi et al "verify" the result from [1] and get to 20ps RMS with 30ps RMS worst case. Unfortunately, they don't write which FPGA they used. (At least i couldnt find it just now) Attila Kinali [1] The lO-ps Wave Union TDC: Improving FPGA TDC Resolution beyond Its Cell Delay, Jinyuan Wu and Zonghan Shi, 2008 IEEE Nuclear Science Symposium Conference [2] A 20ps Resolution Wave Union FPGA TDC with On-Chip Real Time Correction, Ji Qi, Zhi Deng, Hui Gong, Yinong Liu -- Why does it take years to find the answers to the questions one should have asked long ago? _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
