); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] In a message dated 7/7/2007 06:56:54 Pacific Daylight Time, [EMAIL PROTECTED] writes:
>Therefore the qustion: Has anyone of you an theoretical knowledge about >the HP3325 that would explain this behaviour or has anyone of you made >similar findings? In the above example the frequency had been set to >10.000000005 Mhz, square output, 5V amplitude, 2.5V dc offset which >gives an 0 to 5 V when terminated into 50 Ohms. Can it be that the >effect is due to the sqare output? I made some tests whith seeting the >phase of the output signal which led to no noticable changes so there >could be an signifant difference of signal phase behavoiur between sine >and square generstion. Hi Ulrich, Magnus explained nicely how the 3325 phase jumps may happen. For an interesting in-debth analysis on a competitive approach please see Tom's excellent investigation of the FireFox Signal generator on his website (thanks again Tom): _http://www.leapsecond.com/logs/said/4.htm_ (http://www.leapsecond.com/logs/said/4.htm) Our FireFox DDS Signal Generator is another approach to generating signals using a DDS with very high resolution. Due to the finite DDS resolution (either 32 or 48 bits) there is a small phase creep on FireFox, it's about 4.8E-013 at 10MHz, but in our case it's pretty constant - no sudden phase jumps. Tom measured the jitter between the 10MHz reference and the DDS outputs to be around +-0.2ps (at 1s ADEV intervalls). The jitter between the reference and the DDS outputs can go below 1E-016 above 2Ks measurement intervalls. BTW: the FireFox would probably work quite well for your particular test requirements: it has a 3.3V/5V CMOS output and a Sine Wave output. The phase of the outputs can be shifted +-180 degrees in 0.1 degree steps, that may help to find interpolator discontinuities/non-linearities. If necessary, the hardware could generate 16-bit phase offset resolution. One comment: as Tom explains the FireFox has a native DDS mode with 32 bits resolution, this is probably comparable to the HP3325. It also has a fractional-N mode that expands this native resolution to 48+ bits. We are working on a reduced-bandwidth (400MHz instead of 1640MHz) version of FireFox to be introduced next year, maybe even battery-operated and portable - that unit will have a reduced cost point that's more attractive to HAM's etc. That unit will have the 4.8E-013 phase creep mitigated as well :) bye, Said ************************************** See what's free at http://www.aol.com. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.