周波数が時間的に増加していくプログラムについて

function y = chirp(t,varargin) %CHIRP Swept-frequency cosine generator. % Y = CHIRP(T) generates samples of a swept-frequency signal at the time % instances defined in array T. By default, the instantaneous frequency % at time 0 is 0, and the instantaneous frequency one second later is 100 % Hz. % % Y = CHIRP(T,F0,T1,F1) generates samples of a linear swept-frequency % signal at the time instances defined in array T. The instantaneous % frequency at time 0 is F0 Hz. The instantaneous frequency F1 is % achieved at time T1. % % Y = CHIRP(T,F0,T1,F1,method) specifies alternate sweep methods. % Available methods are 'linear', 'quadratic', and 'logarithmic'; the % default is 'linear'. For a logarithmic-sweep, F0 must be greater than % or equal to 1e-6 Hz, which is also the default value. % % Y = CHIRP(T,F0,T1,F1,method,PHI) specifies an initial phase PHI in % degrees. By default, PHI = 0. % % Y = CHIRP(T,FO,T1,F1,'quadratic',PHI,'concave') generates samples of a % quadratic swept-frequency chirp signal whose spectrogram is a parabola % with its concavity in the positive frequency axis. % % Y = CHIRP(T,FO,T1,F1,'quadratic',PHI,'convex') generates samples of a % quadratic swept-frequency signal whose spectrogram is a parabola with % its convexity in the positive frequency axis. % % Y = CHIRP(...,sigtype) specifies sigtype as 'real' or 'complex'; the % default is 'real'. When sigtype is set to 'real', CHIRP generates real % chirp signals. When set to 'complex', CHIRP generates complex chirp % signals. % % EXAMPLE 1: Compute the spectrogram of a linear chirp. % t = 0:0.001:2; % 2 s at 1 kHz sample rate % y = chirp(t,0,1,150); % Start at DC, cross 150 Hz at % % t = 1 s % spectrogram(y,256,250,256,1E3); % Display the spectrogram % % EXAMPLE 2: Compute the spectrogram of a quadratic chirp. % t = -2:0.001:2; % +/-2 s at 1 kHz sample rate % y = chirp(t,100,1,200,'q'); % Start at 100 Hz, cross 200 Hz at % % t = 1 s % spectrogram(y,128,120,128,1E3); % Display the spectrogram % % EXAMPLE 3: Compute the spectrogram of a convex quadratic chirp % t = 0:0.001:1; % 1 s at 1 kHz sample rate % fo = 25; % Start at 25 Hz, % f1 = 100; % go up to 100 Hz % y = chirp(t,fo,1,f1,'q',[],'convex'); % spectrogram(y,256,200,256,1000); % Display the spectrogram. % % EXAMPLE 4: Compute the spectrogram of a concave quadratic chirp % t = 0:0.001:1; % 1 s at 1 kHz sample rate % fo = 100; % Start at 100 Hz, % f1 = 25; % go down to 25 Hz % y = chirp(t,fo,1,f1,'q',[],'concave'); % spectrogram(y,256,200,256,1000); % Display the spectrogram. % % EXAMPLE 5: Compute the spectrogram of a logarithmic chirp % t = 0:0.001:10; % 10 s at 1 kHz sample rate % fo = 10; % Start at 10 Hz, % f1 = 400; % go up to 400 Hz % y = chirp(t,fo,10,f1,'logarithmic'); % spectrogram(y,256,200,256,1000); % Display the spectrogram % % EXAMPLE 6: Compute a complex-valued linear chirp % t = 0:0.001:2; % 2 s at 1 kHz sample rate % fo = -50; % Start at -50 Hz, % t1 = 1; % f1 = 200; % cross 200 Hz at t = 1 s % y = chirp(t,fo,t1,f1,'complex'); % spectrogram(y,256,200,256,1000,'centered'); % Display the spectrogram % % See also GAUSPULS, SAWTOOTH, SINC, SQUARE. % Copyright 1988-2021 The MathWorks, Inc. % References: % [1] Agilent 33220A 20 MHz Function/Arbitrary Waveform Generator % Users Guide, Agilent Technologies, March 2002, pg 298 %#codegen narginchk(1,8); % special case for empty input ([]) if isempty(t) y = zeros(0,1); return end validateattributes(t,{'numeric'},{'real','finite'},'chirp','t',1); t = double(t); % Parse inputs, and substitute for defaults: [f0,t1,f1,method,phi,quadtype,isComplex] = parseOptArgs(varargin{:}); % Initializing output variable y = coder.nullcopy(t); % Computing the signal according to method switch method case 'polynomial' % Polynomial chirp y = cos(2*pi*polyval(polyint(f0),t)); case 'linear' % Linear chirp y = calculateChirp(f0,f1,t1,1,t,phi,isComplex); case 'quadratic' % Compute the quadratic chirp output based on quadtype % Compute the quadratic chirp (upsweep or downsweep) for % complex or concave modes. % For the default 'concave-upsweep' and 'convex-downsweep' modes % call calculateChirp without any changes to the input parameters. % For the forced 'convex-upsweep' and 'concave-downsweep' call % calculateChirp with f0 and f1 swapped and t = fliplr(-t) % For 'convex-upsweep' and 'concave-downsweep' modes if ((f0(1) < f1) && strcmp(quadtype,'convex') || ((f0(1) > f1) && strcmp(quadtype,'concave'))) t = fliplr(-t); f0temp = f1; f1temp = f0(1); else f0temp = f0(1); f1temp = f1; end y = calculateChirp(f0temp,f1temp,t1,2,t,phi,isComplex); case 'logarithmic' % Logarithmic chirp if f0 < 1e-6 coder.internal.error('siglib:chirp:InvalidF0','F0'); else tempVector = repmat(f1/f0,size(t,1),size(t,2)).^(t./t1); instPhi = (t1/log(f1/f0)*f0)*(tempVector-1); if (isComplex) y = exp(1i*2*pi*phi/360).*complex(cos(2*pi*(instPhi)), -cos(2*pi*(instPhi+90/360))); else y = cos(2*pi*(instPhi+phi/360)); end end end end %--------------------------------------------------------------------------- function yvalue = calculateChirp(f0,f1,t1,p,t,phi,isComplex) % General function to compute beta and y for both % linear and quadratic modes. % p is the polynomial order (1 for linear and 2 for quadratic) coder.internal.prefer_const(isComplex); beta = (f1-f0).*(t1.^(-p)); if (isComplex) yvalue = exp(1i*2*pi*phi/360).*complex(cos(2*pi*(beta./(1+p)*(t.^(1+p))+f0*t)),-cos(2*pi*(beta./(1+p)*(t.^(1+p))+f0*t+90/360))); else yvalue = cos(2*pi*(beta./(1+p)*(t.^(1+p))+f0*t+phi/360)); end end %--------------------------------------------------------------------------- function [f0,t1,f1,method,phi,quadtype,isComplex] = parseOptArgs(varargin) % PARSEOPTARGS Parse optional input arguments. % Up to 6 optional input arguments, % f0 - Instantaneous frequency at time 0 % t1 - Reference time % f1 - Instantaneous frequency at time t1 % method - Sweep method % phi - Initial phase % quadtype - Spectrogram shape of quadratic chirp % Flag to keep track of coder target isCodegen = ~coder.target('MATLAB'); % Flag to keep track of output signal type isComplex = false; TFcomprl = false; if ( ~ isempty(varargin)) lastArg = varargin{nargin}; if ( ~ isnumeric(lastArg)) && (strcmpi(lastArg,'complex')) TFrc = strcmpi(lastArg,'complex') || strcmpi(lastArg,'real'); isComplex = true; TFcomprl = true; % checks if the output signal type is coder.const() coder.internal.errorIf((~coder.internal.isConst(lastArg) && ~TFrc),... 'siglib:chirp:CoderConstantExpected'); elseif ( ~ isnumeric(lastArg)) && (strcmpi(lastArg,'real')) TFrc = strcmpi(lastArg,'complex') || strcmpi(lastArg,'real'); isComplex = false; TFcomprl = true; coder.internal.errorIf((~coder.internal.isConst(lastArg) && ~TFrc),... 'siglib:chirp:CoderConstantExpected'); end end % Default value depends upon method f0 = 0; % Flag to check input status of f0 isF0Set = false; % Initialize to default values t1 = 1; f1 = 100; method = 'linear'; phi = 0; quadtype = 'null'; if isCodegen coder.varsize('method',[1,11],[0,1]); coder.varsize('quadtype',[1,7],[0,1]); end % Validation and parsing of each input argument for argIndex = 1:nargin if (TFcomprl) && (argIndex == nargin) break; else input = varargin{argIndex}; if ~isempty(input) switch argIndex case 1 validateattributes(input,{'numeric'},{'vector','finite','real'},'chirp','F0'); % % Deprecated functionality if length(input)>1 % % Y = CHIRP(T,P) specifies a polynomial vector P for the % % instantaneous frequency trajectory of the chirp. if isCodegen coder.internal.error('siglib:chirp:PolynomialNotSupported'); else coder.internal.warning('siglib:chirp:syntaxObsolete'); method = 'polynomial'; end end f0 = double(input); isF0Set = true; case 2 validateattributes(input,{'numeric'},{'scalar','real','positive','finite'},'chirp','T1'); t1 = double(input(1)); case 3 validateattributes(input,{'numeric'},{'scalar','real','finite'},'chirp','F1'); f1 = double(input(1)); case 4 if ischar(input) || isStringScalar(input) % Checking for empty string if ~strcmp(input,'') % % Checking string validity % % Valid input strings optionStrings = {'linear','quadratic','logarithmic'}; method = validatestring(input,optionStrings,'chirp'); end else % Invalid Inputs coder.internal.error('siglib:chirp:InvalidInputType','Method','Chirp','character array',class(input)); end case 5 validateattributes(input,{'numeric'},{'scalar','finite','real'},'chirp','PHI'); phi = double(input(1)); case 6 if ischar(input) || isStringScalar(input) % Checking for empty string if ~strcmp(input,'') % Checking string validity % Valid input strings optionStrings = {'concave','convex'}; quadtype = validatestring(input,optionStrings,'chirp'); end else % Invalid Inputs coder.internal.error('siglib:chirp:InvalidInputType','Shape','Chirp','character array',class(input)); end end end end end % Assigning default value to f0 based on method if ~isF0Set && strcmp(method,'logarithmic') f0 = 1e-6; % Minimum output frequency in Agilent Function generator is 1 microHz end % Quadtype is valid only with quadratic method if ~strcmp(quadtype,'null') && ~strcmp(method,'quadratic') coder.internal.error('siglib:chirp:InvalidMode',quadtype, method); elseif strcmp(method,'quadratic') && strcmp(quadtype,'null') % Determine the shape of the quadratic sweep - concave or convex, % if not defined by user if (f1 > f0) quadtype = 'concave'; % Default for upsweep else quadtype = 'convex'; % Default for downsweep. end end end % [EOF] chirp.m % LocalWords: FO fo Agilent quadtype upsweep downsweep PARSEOPTARGS siglib