getmod.m

阵列信号处理的工具箱

function mod = getmod(method, methodParam, phaseFlag, permFlag)

%GETMOD Returns the coeffients for a selected modulation, e.g. Barker 13.
%
%Synopsis:
%  mod = getmod(method, methodParam)
%  mod = getmod(method, methodParam, phaseFlag)
%  mod = getmod(method, methodParam, phaseFlag, permFlag)
%
%Description:
%  Returns the (complex) coeffients for a selected modulation, e.g. Barker 13.
%  This modulation will be repeated once for every PRI (pulse repetition
%  interval) when used in simulations.
%
%  Different general aspects on modulations (waveforms) can be found in
%  [3,5,10].
%
%Output and Input:
%  mod (CxVectorT): The complex coefficients for the  modulation code.
%  method (StringT): Type of modulation.
%    = 'rect'   : Rectangular pulse. See below for description.
%    = 'gauss'  : Near gaussian pulse [2]. Not Implemented.
%    = 'frank'  : Frank coding. See below for description.
%    = 'barker' : Barker coding. See below for description.
%    = 'chirp'  : Chirp (linear FM) coding. See below for description.
%    = 'PRBS'   : PRBS (Pseudo-Random Binary Sequence) code. See [5] pp. 15-16
%      and [7,8]. Not implemented.
%    = 'GF'	: GF codes, see  See  [9] and [5] pp. 17-18. Not implemented.
%    = 'biRnd': Random binary phase code, see [5] pp. 32-33. Not implemented.
%    = 'multiRnd': Random multi phase code, see [5] pp. 32-34. Not implemented.
%  methodParam (?): Parameters specific to the choosen type of modulation.
%    See below under respective method.
%  phaseFlag [D](IntScalarT) : 1 if a phaseshift of pi radians of the code
%    is wanted. Defaults to zero.
%  permFlag [D](IntScalarT)  : 1 if a fliparound of the code is wanted.
%    i.e. [1 2 3] -> [3 2 1] if permFlag is set. Defaults to zero.
%
%----------
%Rectangular Pulse ('rect').
%Synopsis:
%  mod = getmod('rect',pulseLength);
%
%Description:
%  Creates rectangular modulating coefficients, i.e. all set to one, for the
%  wanted pulselength. See [2] and p. 129-132 in [3] for more information.
%
%Output and Input:
%  pulseLength (IntScalarT): Number of coefficients to return.
%
%----------
%Barker Coding ('barker').
%Synopsis:
%  mod = getmod('barker', codeOrder);
%  mod = getmod('barker', codeOrder, phaseFlag);
%  mod = getmod('barker', codeOrder, phaseFlag, permFlag);
%
%Description:
%  Barker code generation, see [2,3,5,6] for further information.
%
%Output and Input:
%  codeOrder (StringT): Order of code, valid orders are '2a', '2b', '3',
%    '4a', '5', '7', '11' and '13'.
%
%----------
%Frank Coding ('frank').
%Synopsis:
%  mod = getmod('frank', codeOrder);
%  mod = getmod('frank', codeOrder, phaseFlag);
%  mod = getmod('frank', codeOrder, phaseFlag, permFlag);
%
%Description:
%  Frank code generation, see [2,3,4,5] for further information.
%
%Output and Input:
%  codeOrder (IntScalarT) : Order of code. Note: Length of Frank code of
%    order M is M^2.
%
%----------
%Chirp Coding
%Synopsis:
%  mod = getmod('chirp', [fModMax, fSamp, len]);
%  mod = getmod('chirp', [fModMax, fSamp, len], phaseFlag);
%  mod = getmod('chirp', [fModMax, fSamp, len], phaseFlag, permFlag);
%
%Description:
%  Chirp (linear FM) code generation. The phase between samples increases
%  in a rate corresponding to a linear frequaency increase. The start phase
%  is zero and the start frequency is zero.
%  See [2] and p, 132-136 in [3] for further information.
%
%Output and Input:
%  fModMax (RealScalarT): Maximum frequency deviation [Hz] from start
%    to end of pulse.
%  fSamp (RealScalarT): Sampling frequency [Hz].
%  len (IntScalarT): Length of modulation (number of coefficients or samples).
%
%Software Quality:
%  This function is not tested.
%
%----------
%Notations:
%  Data type names are shown in parentheses and they start with a capital
%  letter and end with a capital T. Data type definitions can be found in [1]
%  or by "help dbtdata".
%  [D] = This parameter can be omitted and then a default value is used.
%  When the [D]-input parameter is not the last used in the call, it must be
%  given the value [], i.e. an empty matrix.
%  ... = There can be more parameters. They are explained under respective
%  metod or choice.
%
%Examples:
%  Example 1:
%    % An example with Barker code.
%    ant = defant('expAnt');
%    sig1 = expsig1(ant,'test.dbs');
%    pmod = getmod('barker','13');
%    sig2 = pulscomp(sig1,pmod);
%    sigplot2(sig2,10,':',':');
%    title('After pulse compression.')
%
%  Example 2:
%    % An example with Chirp (linear frequency modulation).
%    len = 1024;	% Number of samples.
%    maxFDev = 500;	% Maximum frequency deviation [Hz].
%    fSamp = 2000;	% Sampling frequency [Hz].
%    Ts = 1/fSamp;	% Sampling time [s].
%    t = linspace(0, Ts*len, len);
%    codeCalc = getmod('chirp',[maxFDev,fSamp,len]);
%    realSig = real(codeCalc);
%    figure,plot(t,realSig)
%    title('Time signal')
%    xlabel('Time [s]')
%
%    freqEst = 1/(2*pi) * diff(unwrap(angle(codeCalc))) * fSamp;
%    figure, plot(t,[0;freqEst])
%    title('Frequency estimation')
%    xlabel('Time [s]')
%    ylabel('Frequency [Hz]')
%
%    spect = fftshift(fft(realSig));
%    f = linspace(-fSamp/2,fSamp/2,len);
%    figure,plot(f,spect)
%    title('Frequency spectrum')
%    xlabel('Frequency [Hz]')
%    %Expected result :
%    %  The frequency of the time signal shall increase.
%    %  The estimation of frequency shall be a straight line with upward
%    %  direction an through origo (from 0 Hz to 500 Hz).
%    %The frequency spectrum shall reside mainly within +- 500 Hz.
%
%Software Quality:
%  (About what is done to ascertain software quality. What tests are done.)
%
%References:
%  [1]: Bj鰎klund S.: "DBT, A MATLAB Toolbox for Radar Signal Processing.
%    Reference Guide", FOA-D--9x-00xxx-408--SE, To be published.
%  [2]: Kingsley S., Quegan S.: "Understanding Radar Systems",
%   McGraw-Hill 1992. ISBN 0-07-707426-2. Page 150-154.
%  [3]: Levanon N.: "Radar Principles", Wiley 1988. ISBN 0-471-85881-1.
%  [4]: Frank R.L.: "Polyphase Codes with Good Nonperiodic Correlation
%    Properties", IEEE Trans. on Information Theory, IT-9 (1963), pp. 43-45.
%  [5]: Oreborn U.: "En analys av v錱former f鰎 bistatiska radarsystem",
%    Defence Research Establishment, Sweden, FOA Report C 30765-3.3,
%    June 1994, in Swedish.
%  [6]: Barker R.H.: "Group Synchronizing of Binary Digital Systems", in
%    Communication Theory (W. Jackson, ed.), Academic Press 1953, pp. 273-287.
%  [7]: Henriksson U.:"Signalteori D", Department of Electrical Engineering,
%    Link鰌ing University, Sweden, June 1990, pp. 131-132.
%  [8]: Bj鰎klund S.: "Implementation einer Schrittweitensteuerung f黵
%    einen Kompensator f黵 akustische Echos", Master of Science Thesis D85,
%    Technische Hochshule Darmstadt, Germany, February 1993, pp. 26-27.
%  [9]: Carlsson E.J.:"Low Probability of Intercept (LPI) Techniques and
%    Implementations for Radar Systems", Proceedings of the 1988 IEEE
%    National Radar Conference, pp. 56-60.
%  [10]: Gr鰊berg F.:"Tyst radar - synpunkter p