Pascal Gollor revised this on 18 Oct 2018

test.m

% @author Pascal Gollor % @date 2018-10-18 % % create two signals with random phase offset and try to reduce the offset % via fft analysis % clear all; clear figures; clc; %% values % samples N = 1000; % signal periods periods = 2; % amplitude signal 1 amp1 = 1; % amplitude signal 2 amp2 = 1.4; %% signal generation Fs = N / periods; T = 1 / Fs; t = 0:T:periods - T; freq = 1; phase_offset = rand(1)*(pi/2); % signal s1 = 2 + amp1 * sin(2* pi * freq * t); s2 = 1 + amp2 * sin(2* pi * freq * t + phase_offset); % noise hi = 0.05; lo = -0.05; n1 = lo + (hi-lo) * rand([1 N]); n2 = lo + (hi-lo) * rand([1 N]); s1 = s1 + n1; s2 = s2 + n2; % true phase ofset phase_offset %% calculation % fft fft_s1 = fft(s1); fft_s2 = fft(s2); % remove dc component offset1 = fft_s1(1) / N; fft_s1(1) = 0; fft_s2(1) = 0; % calculated offset phase_rad = angle(fft_s1(1:end/2)/fft_s2(1:end/2)) % signal shiftig fft_s2_shift = fft_s2 .* exp(-j*t*phase_rad); s2_shift_comp = ifft(fft_s2_shift); s2_phase = angle(s2_shift_comp); s2_phase(s2_phase > 0) = 1; s2_phase(s2_phase < 0) = -1; s2_shift = abs(s2_shift_comp) .* s2_phase + offset1; %% plotting figure(1); plot(t, s1); hold on; plot(t, s2); plot(t, s2_shift); hold off; legend('original signal', 'shifted signal', 'back shifted signal')