Hi Regardless of what you call the “ 1 Hz normalized noise “ of a digital phase detector, it does predict what the noise floor does on it as the reference frequency is changed over some reasonable range. This has been demonstrated a lot of times and on a lot of different parts.
Based on a number of RF designs using them ( and using gates for RF purposes ) the basic gate is what is at fault here. They are noisy and that noise changes with frequency. Frequency goes up / noise goes up. There are very good reasons for this. Getting a gate with a noise figure below 6 db is highly unlikely …. That is what you would have to do in order to make a gate based circuit measure a lower noise floor than the DBM based approach. Folks have spent a lot of time searching for the magic “zero noise gate”. The sine wave component present at the DBM output at 2X the input frequency ( in the case of the phase noise test setup) are *way* higher than the highest noise you are after. You put in 10 MHz or 100 MHz and you go up to *maybe* 100 KHz on the noise. With a sound card, even getting to 100 KHz is going to be a challenge. 20 KHz may be the max. Knocking down the 2 x Fin component with a low pass filter is pretty easy. Indeed the sound card or audio spectrum analyzer likely has some filtering already. The design and implementation of an adequate LPF is far from the biggest challenge that the person building the circuit will face. Indeed 1/F noise and noise corners do matter. All of the above has been simply talking about noise floor. Gates have significant 1/F issues along with their other “features”. This carries over to the detectors based on them. As the gate speed goes up ( and the floor typically comes down), the 1/F corner normally moves up …. Bob > On Jul 11, 2022, at 8:05 AM, Mike Monett via time-nuts > <time-nuts@lists.febo.com> wrote: > > To Bob kb8tq > > Figure Of Merit sounds like a useless number. I have a different > approach that yields immediate and useful results. Before I explain > my method, let me introduce myself. > > In 1970, I invented, and Memorex patented, the original > zero-deadband phase-frequency detector. You can see it in page 3 of > my '234 patent at https://patents.google.com/patent/US3810234A/ > > This invention soon led to another invention of tremendous > significance to today's world. > > In 2014, researchers published a study in the journal Supercomputing > Frontiers and Innovations estimating the storage capacity of the > Internet at 1e24 bytes, or 1 million exabytes. > > When I started working for Memorex, an IBM 2314 disk pack could > store 29.2 million bytes. At that rate, today's internet would > require 1e24/29e6=3.44e16, or 34,400,000,000,000,000 IBM 2314 disk > drives. This is an impossible number. Other estimates give equally > outrageous numbers. > > The problem in those days was improvements in disk drive capacity > were basically trial and error. This is a slow and very expensive > business. > > My new invention allowed peering into the hard disk and separating > out all the variables that affect performance. With this > information, researchers could see the effect of changes and quickly > optimize the performance. This allowed the tremendous improvement in > tape and disk drive capacity that now allows the internet to store > all the needed data. > > You can see how this invention works in the Katz paper at > https://tinyurl.com/2bmuz3n2 > > Now for my new method. > > The schematic for a phase-frequency detector is shown in > DBAND2S.PNG. In operation, a pulse arrives at the DATA pin and pin > U1Q goes high. Then a pulse arrives at the VCO pin and pin U2Q goes > high. > > This allows the NAND gate to bring the CLR signal low, which > immediately resets both d-flops. > > The result is shown in ZERODB.PNG. It is a very narrow pulse with > both d-flops superimposed. > > This is the basis for my new approach. Simply tie both inputs of the > PFD together and measure the noise spectrum of the output. (Of > course, you have to ensure that both outputs match at zero error.) > > Once you have the PFD noise, you can enable the loop and measure the > total noise spectrum. Then simply subtract the PFD spectrum to get > the OCXO noise. If you have two identical VCXO's, each one > contributes half the noise. > > I don't know if this method would work with a double-balanced mixer. > The problem is a DBM requires quadrature signals, so the noise is a > function of the OCXO noise as well as the mixer diodes. But the OCXO > noise is what you are trying to measure. > > This method works with the PFD since only a single pulse is needed > to activate both d-flops, so you are measuring only the PFD noise. > > Et Voila. > > Now that you can measure the OCXO noise, you might want to try your > hand at designing an oscillator with minimum noise. You immediately > run into a problem. The high Q of the crystal means the oscillator > takes a very long time to start up. > > I solved this problem in my OSC.ZIP file at > https://tinyurl.com/2p9yrxmy > > Steve Wilson is me. Just start at the README.TXT file and you are on > your way. > > Now that you are a fully qualified Time-Nut, you might be interested > in some of the following papers: > > Rohde, 1994 How to improve phase noise by multiple varicaps in parallel > http://www.arrl.org/files/file/Technology/ard/rohde94.pdf > > Leeson Equation > http://rfic.eecs.berkeley.edu/~niknejad/ee242/pdf/eecs242_lect22_phasenoise.pdf > > Oscillator Phase Noise: A Tutorial > Thomas H. Lee, Member, IEEE, and Ali Hajimiri, Member, IEEE > http://smirc.stanford.edu/papers/JSSC00MAR-tom.pdf > > Hajamiri > Virtual Damping and Einstein Relation in Oscillators > https://authors.library.caltech.edu/523/1/HAMieeejssc03.pdf > <DBAND2S.PNG><ZERODB.PNG>_______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com