matlab_pinpu.zip_matlab；频谱分析；带通滤波

function [frequency_time,amplitude,start_time,end_time] = lab1_p4(x,fs) % Divide the entire time interval into several time frames frame_length = 1; % This part only requires 1 sec as time section frame_size = frame_length * fs; % Size of each frame (number of samples inside one frame). NOTE: fs is also the number of sample per period(frame) number_of_frame = length(x)/frame_size; % X has length(x) samples total_signal_time = length(x)/fs; frame_time = total_signal_time/number_of_frame; frequency_array = [0]; % An array that contains all the frequencies appear in each frame. If frequencies do not appear, zeros will be added. amplitude_array = [0]; % An array that contains all the amplitudes appear in each frame. If corresponding frequencies do not appear, zeros will be added. start_array = [0]; % An array that contains all the start time for different signals end_array = [0]; % An array that contains all the end time for different signals. Initially, it contains zeros only array_counter = 0; % A counter for array index end_isdone = [zeros(1,fs)]; % Check if the endtime storage is done % Analyse signal section by section for i = 1:number_of_frame % i = ith frame start_sample = (i - 1) * frame_size + 1; % Matlab starts from index 1 end_sample = i * frame_size; % End at each frame_size subx = x(start_sample:end_sample); % Analysis of signal from start_sample to end_sample [frequency_frame,amplitude_frame] = lab1_p3(subx,fs); % Analyse one frame at one time % frequency_frame will contain all the frequencies appear in each frame % amplitude_frame will contain all the amplitudes appear in each frame for frame_index = 1:length(frequency_frame); % Dummy variable for checking if the value is already inside frequency_array[] if ( sum(find( frequency_array == frequency_frame(frame_index))) == 0 ) % If frequency_frame(frame_index) is not found inside the frequency_array. Try to find frequency_frame(frame_index) in frequency_array array_counter = array_counter + 1; frequency_array(array_counter) = frequency_frame(frame_index); % Store the unfound value into the frequency_array % Assume different frequencies have different amplitudes amplitude_array(array_counter) = amplitude_frame(frame_index); % If frequency is not found, then amplitude cannot be found, so put that value into the amplitude_array start_array(array_counter) = (i - 1) * frame_time; end end for endtime_index = 1:length(frequency_array) if (sum(find( frequency_frame == frequency_array(endtime_index))) == 0 && end_isdone(endtime_index) ~= 1) % If frequency_array(endtime_index) is not found in frequency_frame and it is not manipulated before, then the signal with this frequency is terminated. Try to find frequency_array(endtime_index) in frequency_frame, if it is not found, then it stops end_array(endtime_index) = (i - 1) * frame_time; % Store endtime to corresponding index end_isdone(endtime_index) = 1; end end end frequency_time = frequency_array; amplitude = amplitude_array; start_time = start_array; end_array = [end_array zeros(1,length(frequency_array)-length(end_array))]; % Adding zeros in case of some of the signals still running for endtime_end = 1:length(frequency_array) % If any signals do not stop, force them to stop at the end, i.e. total_signal_time if( end_array(endtime_end) == 0 ) end_array(endtime_end) = total_signal_time; end end end_time = end_array; end