[time-nuts] DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

[Mike Monett]

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
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