main_03_ksg

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% 주제3: 신호 생성, 주파수 변환, 파워 계산을 합니다.
% 2025-04-02 / 김상곤
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clc; clear; close all

% 입력 변수 준비
T = 1;
t0 = 0;
dt = 1/1000;
N = T/dt;
Fs = 1/dt;
df = 1/T;
freq = 0:df:Fs-df;

time_array = t0:dt:T-dt; % size: 1 x N
freq_array = [50 70 110]; % size: 1 x 주파수 성분 수
ampl_array = [10 2 5]; % size: 1 x 주파수 성분 수
phaz_array = [0 0 0]; % size: 1 x 주파수 성분 수

% sinusoidal 신호 생성
signal = get_sinusoidal(time_array,freq_array,ampl_array,phaz_array); % size: 1 x length(time_array)

% hanning window 적용
signal_h = signal.*hanning(N).';  % size: 1 x length(time_array)

% 주파수 데이터로 변환
Spectrum = fft(signal,[],2)/N;  % size: 1 x length(freq)
Spectrum_h = fft(signal_h,[],2)/N; % size: 1 x length(freq)

% Auto Power Spectrum 계산
APS = Spectrum.*conj(Spectrum); % size: 1 x length(freq)
% Auto Power Spectrum 계산 (hanning window 적용)
APS_h = Spectrum_h.*conj(Spectrum_h); % size: 1 x length(freq)

% Power Sum
pwr_sum_time = calc_pwr_sum_time(signal); % 결과: 64.5
pwr_sum_freq = calc_pwr_sum_freq(Spectrum); % 결과: 64.5
% Power Sum (hanning window 적용)
pwr_sum_time_h = calc_pwr_sum_time(signal_h); % 결과: 24.163
pwr_sum_freq_h = calc_pwr_sum_freq(Spectrum_h); % 결과: 24.163

ratio_energy = sqrt(pwr_sum_time/pwr_sum_time_h); % 1.63 = hanning window의 Energy Coeff.
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% Plotting
figure(1)
plot(time_array,signal,'k;orignal;','linewidth',3)
plot(time_array,signal_h,'g;windowed;','linewidth',2)
xlabel('Time [sec]'); ylabel('Acceleration [m/s^2]')
title('< 윈도우 적용 전후 시간 신호 비교 >')

figure(2)
plot(freq,APS,'k;orignal;','linewidth',3)
plot(freq,APS_h,'g;windowed;','linewidth',2)
xlabel('Frequency [Hz]'); ylabel('Auto Power Spectrum [(m/s^2)^2]')
title('< 윈도우 적용 전후 Auto Power Spectrum 비교 >')