46 lines
1.8 KiB
Matlab
46 lines
1.8 KiB
Matlab
function x = generate_heartbeat(amplitude, frequency, phase, fs, duration, duty)
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% GENERATE_SINE: returns a matrix of sampled heart monitor wave
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% CONTRIBUTORS:
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% Alex Nguyen: Original Author
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% Conner Hsu: Reviewed Code and Assisted in polishing
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% DOCUMENTATION:
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% phase shift is in number of periods
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% fs is the sampling frequency: how many sample points per second
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% duration is time in seconds
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% duty cycle should be a number between 0 and 0.5.
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% duty of 0 or less would return 0 for all sample points
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% duty of 0.5 or less would return a heartbeat signal since there would be
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% equal amount of space within 1 period to have the right and left sides be equal
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% duty of greater than 0.5 but less than 1 would return a slope starting at that duty i.e.
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% the left side but leaving little room to the right side
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% duty of between 1 and 2 would give a sawtooth wave in the +amplitude.
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% duty greater than 2 would return 0 for all sample points
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% initialize local variables from input arguments
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n = fs * duration; % number of samples (length of matrix)
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dt = 1 / fs; % sampling period: time between two sample points
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% initialize a one dimensional zero matrix to be populated
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x = zeros(1, n);
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% populate the matrix
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for i = 1:n
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t = i * dt; % time at the i'th sample
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st = mod(frequency * t - phase, 1);
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if (duty-(duty / 2) < st && st < duty)
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slope = amplitude / duty;
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intercept = -0.5 * amplitude;
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x(i) = slope * st + intercept;
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elseif (duty < st && st < duty+(duty / 2))
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slope = amplitude / duty;
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intercept = -amplitude;
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x(i) = slope * st + (1.5 * intercept);
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else
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x(i) = 0;
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end
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end |