LFM.zip_LFM幅度_LFM幅度谱_lfm_lfm 调频_lfm分析

function LFM(B,T); time_B_product = B * T; if(time_B_product < 5 ) fprintf('************ Time Bandwidth product is TOO SMALL ***************') fprintf('\n Change B and or T') return else end % Compute alpha mu = 2. * pi * B / T; npoints = 5 * B * T+1; % Determine sampling times delt = linspace(-T/2., T/2., npoints); % % Compute the complex LFM representation Ichannal = cos(mu .* delt.^2 / 2.); % Real part Qchannal = sin(mu .* delt.^2 / 2.); % Imaginary Part LFM = Ichannal + sqrt(-1) .* Qchannal; % complex signal %Compute the FFT of the LFM waveform LFMFFT = fftshift(fft(LFM)); % Plot the real and Inginary parts and the spectrum sampling_interval = T / npoints; freqlimit = 0.5 / sampling_interval; freq = linspace(-freqlimit,freqlimit,npoints); figure(1) plot(delt,Ichannal,'k'); axis([-T/2 T/2 -1 1]) grid xlabel('Time - seconds') ylabel('Units of Waveform') title('Real part of an LFM waveform') figure(2) plot(delt,Qchannal,'k'); axis([-T/2 T/2 -1 1]) grid xlabel('Time - seconds') ylabel('Units of Waveform') title('Imaginary part of LFM waveform') figure(3) plot(freq, abs(LFMFFT),'k'); %axis tight grid xlabel('Frequency - Hz') ylabel('Amplitude spectrum') title('Spectrum for an LFM waveform')