chirp linear modulation in ultra-wide band

% t1 = 0:0.001:1;            % 2 secs @ 1kHz sample rate
% y1 = chirp(t1,0,1,500);     % Start @ DC,
%                           %   cross 150Hz at t=1 sec
% spectrogram(y1,256,250,256,1E3,'yaxis') %S = spectrogram(x,window,noverlap,nfft,fs)

% t2 = 0:1/2000:1;            % 2 secs @ 1kHz sample rate
% y2 = chirp(t2,500,1,1000);     % Start @ DC,
%                           %   cross 150Hz at t=1 sec
% spectrogram(y2,256,250,256,2E3,'yaxis'); %S = spectrogram(x,window,noverlap,nfft,fs)


% t3 = 0:1/3000:1;            % 2 secs @ 1kHz sample rate
% y3 = chirp(t3,1000,1,1500);     % Start @ DC,
%                           %   cross 150Hz at t=1 sec
% spectrogram(y3,256,250,256,3E3,'yaxis') %S = spectrogram(x,window,noverlap,nfft,fs)