> > Modern ECL parts aren't necessarily that bad compared to the old MECL > > stuff. > > My experience goes all the way back to the MECL 1000 series that was > discontinued 30 years ago. I designed many synthesizers around them > for Zeta Labs. Every newer family of ECL line receivers has been faster > and had worse phase noise, in my experience.
Which is odd because the jitter specs have gotten better -- at least, going by the promises and hype in the data sheets. It sounds like the newer ECL parts' wider bandwidth is folding more noise into the output signal. > This is a very tricky topic. When measuring the phase noise of a non > sine wave, there are dependencies on how the measurement is done. > What is the measurement bandwidth? Etc. > > In some cases, the noise is mostly common mode, and therefore will > depend on the common mode rejection ratio (if any) of your measurement > circuit. I'm measuring it with a 3048A, feeding the DBM directly from one of the MC100EL16P's output pins via a 0.1 uF cap. Both output pins are tied to ground with 200 ohms, per Q12 at http://www.pulseresearchlab.com/faqs/ecl_ques/ecl_Q9-Q12.htm . Input-wise, I just tried a T1-1 balun instead of the single-ended termination I was using before, and got exactly the same results (floor at circa -148 to -150 dBc/Hz at 100 MHz, but only -140 dBc/Hz at 10 MHz.) That, I thought was interesting. -148 dBc/Hz was always the 'rule of thumb' for the older ECL families from what I've read, and since it's not sensitive to input configuration or power-supply bypassing, it must be the process floor. There was no LC or other bandpass filtering at the input, but the sources are decent-quality OCXOs in both cases so I don't think I'm feeding it too much broadband noise to begin with. Maybe another T1-1 at the output would help, but I don't see any reason to think so. -- john, KE5FX _______________________________________________ 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.