All this talk about interpolation reminds me of a little neat chip by Analog Devices, AD9500. It's programmable digital delay, bit, with lops resolution with a loons full-scale range. I believe (from app notes) you can push it to 100us FS, giving 390ns resolution. I think the minimum jitter at the lowest FS was about lops. The AD9500 is cell and the 9501 is TTS.
http://pdf1.alldatasheet.com/datasheet-pdf/view/48545/AD/AD9500.html app note http://www.analog.com/static/imported-files/application_notes/105895411AN-260.pdf Bob ----- Original Message ----- From: Murray Greenman To: [email protected] Sent: Sunday, June 27, 2010 3:14 PM Subject: [time-nuts] Yet another GPSDO - locking to 10MHz I have a design which locks a high performance 10MHz OCXO to a 10MHz source which should work equally well with the LEA5, or any source of 5 or 10MHz. I designed it for use with a distributed factory GPS reference which has picked up noise, hum and phase modulation, in order to deliver a high quality but GPS locked reference direct to equipment. The design adds nearly three orders of improvement. Essentially it divides the incoming 10MHz by 16384 and compared the phase with a similar division from the OCXO, within an ATTiny2313 micro. The phase detector is a D-flip-flop type implemented in software (in interrupts), and it delivers a locked reference with ADev around 10e-12 for Tau between 1s and 20s. The micro also keeps a real time clock and does various background monitoring and telemetry tasks. There is PC monitoring software as well. There are only four chips in the design. While I can't share the code (belongs to my employer), the idea is simple enough and I could share the schematic. Eight of these units have been built. I used the excellent Rakon STP2402E OCXO. Regards, Murray Greenman ZL1BPU _______________________________________________ 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.
