来源：http://www.mathworks.cn/matlabcentral/fileexchange/22038-phase-noise-to-jitter/content/Pn2Jitter.m
function Jitter = Pn2Jitter(f, Lf, fc)
%
% Summary: Jitter (RMS) calculation from phase noise vs. frequency data.
%
% Calculates RMS jitter by integrating phase noise power data.
% Phase noise data can be derived from graphical information or an
% actual measurement data file.
%
% Usage:
% Jitter = Pn2Jitter(f, Lf, fc)
% Inputs:
% f: Frequency vector (phase noise break points), in Hz, row or column.
% Lf: Phase noise vector, in dBc/Hz, same dimensions, size(), as f.
% fc: Carrier frequency, in Hz, a scalar.
% Output:
% Jitter: RMS jitter, in seconds.
%
% Examples:
% [1] >> f = [10^0 10^1 10^3 10^4 10^6]; Lf = [-39 -73 -122 -131 -149];
% >> Jitter = Pn2Jitter(f, Lf, 70e6)
% Jitter = 2.3320e-011
% Comparing fordahl application note AN-02-3{*} and jittertime.com{+}
% calculations at fc = 70MHz
% Pn2Jitter.m: 23.320ps
% AN-02-3 (graphical method): 21.135ps
% AN-02-3 (numerical method): 24.11ps
% Aeroflex PN9000 computation: 24.56ps
% JitterTime.com calculation: 23.32ps
%
% {*} fordahl Application Note AN-02-3:
% "Phase noise to Jitter conversion"
% http://fordahl.com/images/phasenoise.pdf
% As of 11 May 2007 it also appears here:
% http://www.metatech.com.hk/appnote/fordahl/pdf/e_AN-02-3.pdf
% http://www.metatech.com.tw/doc/appnote-fordahl/e-AN-02-3.pdf
%
% {+} JitterTime Consulting LLC web calculator
% http://www.jittertime.com/resources/pncalc.shtml
% As of 5 May 2008
%
% [2] >> f = [10^2 10^3 10^4 10^5 10^6 10^7 4.6*10^9];
% >> Lf = [-82 -80 -77 -112 -134 -146 -146 ]; format long
% >> Jitter = Pn2Jitter(f, Lf, 2.25e9)
% Jitter = 1.566598599875678e-012
% Comparing ADI application note{$} calculations at fc = 2.25GHz
% Pn2Jitter.m: 1.56659859987568ps
% MT-008: 1.57ps
% Raltron {&}: 1.56659857673259ps
% JitterTime: 1.529ps--excluding the (4.6GHz, -146) data point,
% as 1GHz is the maximum allowed
% {$} Analog Devices, Inc. (ADI) application note MT-008:
% "Converting Oscillator Phase Noise to Time Jitter"
% http://www.analog.com/en/content/0,2886,760%255F%255F91502,00.html
% {&} Raltron web RMS Phase Jitter calculator:
% "Convert SSB phase noise to jitter"
% http://www.raltron.com/cust/tools/osc.asp
% Note: Raltron is restricted to f(min) = 10Hz;
% therefore it cannot be used in this example [1].
%
% [3] >> f = [10^2 10^3 10^4 200*10^6]; Lf = [-125 -150 -174 -174];
% >> Jitter = Pn2Jitter(f, Lf, 100e6)
% Jitter = 6.4346e-014
% Comparing ADI application note{$} calculations at fc = 100MHz
% Pn2Jitter.m: 0.064346ps
% MT-008: 0.064ps
% JitterTime: 0.065ps
%
% Note:
% f and Lf must be the same length, lest you get an error and this
% Improbable Result: Jitter = 42 + 42i.
%
% (A spreadsheet, noise.xls, is available from Wenzel Associates, Inc. at
% http://www.wenzel.com, "Allan Variance from Phase Noise."
% It requires as input tangents to the plotted measured phase noise data,
% with slopes of 1/(f^n)--not the actual data itself--for the
% calculation. The app. note from fordahl discusses this method, in
% addition to numerical, to calculate jitter. This graphical straight-
% line approximation integration technique tends to underestimate total
% RMS jitter.)
%
% [4] Data can also be imported directly from an Aeroflex PN9000 ASCII
% file, after removing extraneous text. How to do it:
% (1) In Excel, import the PN9000 data file as Tab-delimited data,
% (2) Remove superfluous columns and first 3 rows, leaving 2 columns
% with frequency (Hz) and Lf (dBc/Hz) data only.
% (With the new PN9000 as of April 2006, only the first row
% is to be removed, and there are only two columns.
% I may take advantage of this in an updated version of this
% program,thereby eliminating the need to edit the data),
% (3) Save As -> Text (MS-DOS) (*.txt), e.g., a:\Stuff.txt,
% (4) At the MATLAB Command Window prompt:
% >> load 'a:\Stuff.txt' -ascii
% Now Stuff is a MATLAB workspace variable with the
% phase noise data,
% (5) >> Pn2Jitter(Stuff(:,1), Stuff(:,2), fc);
% (assuming fc has been defined)
% One 10MHz carrier data set resulted in the following:
% Pn2Jitter.m: 368.33fs
% PN9000 calculation: 375fs
%
% Runs at least as far back as MATLAB version 5.3 (R11.1).
%
% Copyright (c) 2005 by Arne Buck, Axolotol Design, Inc. Friday 13 May 2005
% arne (d 0 t) buck [a +] alum {D o +} mit (d 0 +} e d u
% $Revision: 1.2 $ $Date: 2005/05/13 23:42:42 $
%
% License to use and modify this code is granted freely, without warranty,
% to all as long as the original author is referenced and attributed
% as such. The original author maintains the right to be solely
% associated with this work. So there.
% Bug fixes to resolve problematic data resulting in division by 0, or
% excessive exponents beyond MATLAB's capability of realmin (2.2251e-308)
% and realmax (1.7977e+308); no demonstrable effect on jitter calculation
% AB 18May2005 Fix /0 bug for *exactly* -10.000dB difference in adjacent Lf
% AB 24May2005 Fix large and small exponents resulting from PN9000 data
% AB 11May2007 Improve documentation, update URLs
% AB 5May2008 Verify and update URLs
tic
%% It's almost nine o'clock. We've got to go to work.
L = length(Lf);
if L == length(f)
% Fix ill-conditioned data.
I=find(diff(Lf) == -10); Lf(I) = Lf(I) + I/10^6; % Diddle adjacent Lf with
% a diff=-10.00dB, avoid ai:/0
% Just say "No" to For loops.
lp = L - 1; Lfm = Lf(1:lp); LfM = Lf(2:L); % m~car+, M=cdr
fm = f(1:lp); fM = f(2:L); ai = (LfM-Lfm) ./ (log10(fM) - log10(fm));
% Cull out problematic fine-sieve data from the PN9000.
Iinf = find( (fm.^(-ai/10) == inf) | fm.^(-ai/10)<10^(-300)); % Find Inf
fm(Iinf) = []; fM(Iinf-1) = []; Lfm(Iinf) = []; LfM(Iinf-1) = [];
ai(Iinf) = []; f(Iinf) = []; Lf(Iinf) = [];
% Where's the beef?
Jitter = ...
1/(2*pi*fc)*sqrt(2*sum( 10.^(Lfm/10) .* (fm.^(-ai/10)) ./ (ai/10+1)...
.* (fM.^(ai/10+1) - fm.^(ai/10+1)) ));
else
disp('> > Oops!');
disp('> > > The f&Lf vector lengths are unequal. Where''s the data?')
Jitter = sqrt(sqrt(-12446784));
end % if L
toc
