Hi Magnus, I know what you mean about not needing a quadrature splitter - if you have a very wide phase or delay tuning range - but I'm picturing getting most of the way to quadrature with a fixed structure for a given frequency, and only fine-tuning the phase over a narrow range, in order to minimize the PLL's overall noise contribution. This should also keep it monotonic - too wide a range may let it get stuck on the humps. For amplitude calibration, I'm picturing rearranging the splitter ports or guts somehow (as simply as possible) to present the DUT signal to the mixer at 0 or 180 degrees, which should give a maximum DC out. BTW I had never heard of the Tayloe detector, but it appears to be the method (4x f multiplier then digital quadrature divide) used in lock-in analyzers, and I have used the same in a number of projects. Azelio wrote: "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." Azelio, this is a well known technique - I haven't described anything new, just a particular implementation I've been pondering. Ed

Hi If you dig into the various books on phase noise, they do go into other ways to measure it. The bottom line is that things like frequency discriminators are quite noisy (floor wise) compared to a single mixer. Bob > On Jul 10, 2022, at 10:26 AM, ed breya via time-nuts <time-nuts@lists.febo.com> wrote: > > Hi Magnus, > > I know what you mean about not needing a quadrature splitter - if you have a very wide phase or delay tuning range - but I'm picturing getting most of the way to quadrature with a fixed structure for a given frequency, and only fine-tuning the phase over a narrow range, in order to minimize the PLL's overall noise contribution. This should also keep it monotonic - too wide a range may let it get stuck on the humps. > > For amplitude calibration, I'm picturing rearranging the splitter ports or guts somehow (as simply as possible) to present the DUT signal to the mixer at 0 or 180 degrees, which should give a maximum DC out. > > BTW I had never heard of the Tayloe detector, but it appears to be the method (4x f multiplier then digital quadrature divide) used in lock-in analyzers, and I have used the same in a number of projects. > > > Azelio wrote: > "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." > > Azelio, this is a well known technique - I haven't described anything new, just a particular implementation I've been pondering. > > Ed > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com

Hi Ed, On 7/10/22 20:26, ed breya via time-nuts wrote: > Hi Magnus, > > I know what you mean about not needing a quadrature splitter - if you > have a very wide phase or delay tuning range - but I'm picturing > getting most of the way to quadrature with a fixed structure for a > given frequency, and only fine-tuning the phase over a narrow range, > in order to minimize the PLL's overall noise contribution. This should > also keep it monotonic - too wide a range may let it get stuck on the > humps. Well, the traditional method is to lock it up. When you do that Quadrature (PM) comes for free, but In-phase (AM) does not. The lock require either oscillator to be frequency steerable to achieve lock. If that is not what you want to do, well then you can use a non-synchronous method and then a quadrature splitter is the way to go. This is essentially what the modern oversampling measurement devices do anyway. They just sample the waveforms, convert the IQ into amplitude and phase, and then decimate down from that. Comparison with reference is then done in that context after the fact. Frequency errors can be handled within some fairly flexible range. Similarly, just mixing unlocked sources with I/Q setup produces some beat-note and if you get that as I/Q you can do more or less the same thing. > > For amplitude calibration, I'm picturing rearranging the splitter > ports or guts somehow (as simply as possible) to present the DUT > signal to the mixer at 0 or 180 degrees, which should give a maximum > DC out. For amplitude measurement, you want the in-phase component rather than the quadrature component, if they are locked that is. Using a normal lock, the direct lock phase-detector actually gives you the quadrature, so you need the splitter to get the In-phase too. For non-synchronous receivers, you need to track the beat-note to sort out what is the in-phase and quadrature for AM and PM respectively. An abs/arctan function (such as CORDIC) will convert I/Q samples nicely and the frequency error will be just a phase-ramp on the detected phase. > > BTW I had never heard of the Tayloe detector, but it appears to be the > method (4x f multiplier then digital quadrature divide) used in > lock-in analyzers, and I have used the same in a number of projects. Yes. It is fairly widely used these days. Seems to have good enough properties for many things. > > > Azelio wrote: > "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." > > Azelio, this is a well known technique - I haven't described anything > new, just a particular implementation I've been pondering. Indeed. There is many ways to measure without an actual reference. There might be other oscillators, but they are not "reference" in the way of a voltage reference for instance. Cheers, Magnus