How can you measure something, any type of measure, not only PN, without a reference? Voltmeters need voltage references, "timemeters" (and frequency meters) need time references.
On Sun, Jul 10, 2022 at 1:47 AM ed breya via time-nuts <[email protected]> wrote: > > I've been following the thread about Erik's DIY PN analyzer, and > wondering if it might be easy enough to use a frequency discrimination > method. I'm opening this in a different thread to avoid muddying the > water on the original (and long) one. > > What I'm picturing is putting the DUT's output into a quadrature power > splitter that optionally has a voltage-tuned slight phase shift feature. > The I and Q outputs would go into the DBM and produce the nearly-zero DC > plus baseband signal for analysis as in the original story. > > If the quadrature is precise and stable enough, the DC out should be > close to zero, and since the baseband is ultimately AC coupled to the > analyzer, small offset should be OK, within reason. > > If this is not sufficient, then having a phase tuning feature could be > used to form a PLL to hold the DC at zero. The big difference here is > that instead of locking a separate reference source to the DUT, the > relative phase at the mixer just has to be fine tuned to maintain the > output DC. The same sorts of PLL requirements are encountered to get the > results, but no external reference (and its noise and lock range etc > issues) is needed. > > The downside is that a different quadrature splitter would probably be > needed for each DUT frequency to be applied - I'm picturing ones for 5 > and 10 MHz initially. Those 90 degree broadband splitters that Mike > mentioned seem very interesting too. > > There is still the necessity of calibration, either way. > > Ed > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe send an email to [email protected] _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe send an email to [email protected]
