58 lines
1.7 KiB
Matlab
58 lines
1.7 KiB
Matlab
function x = generate_trapezoid(amplitude, frequency, phase, fs, duration, duty)
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% GENERATE_TRAPEZOID: returns a matrix of sampled square wave
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% CONTRIBUTORS:
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% Daniel Doan: Author
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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 1.
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% duty of 0.5 would have 2 trapezoids in first half of each cycle
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% example of wave with duty of 0.5, where the peaks are amplitude/2:
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%
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% ____
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% / \
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% / \ ________________
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% \ /
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% \____/
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%
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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;
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% periodic ramp from 0 to 1
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% progression through a cycle
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st = mod(frequency * t - phase, 1);
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slope = (amplitude/2) / (duty/8);
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if(st < duty)
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if(st <= duty/8)
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x(i) = slope * st;
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else
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if(st <= 5*duty/8)
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x(i) = amplitude/2 - slope * (st-(3*duty/8));
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end
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if(st <= 3*duty/8)
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x(i) = amplitude/2;
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end
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if(st >= 5*duty/8)
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x(i) = -amplitude/2;
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end
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end
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if(st >= 7* duty/8)
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x(i) = -amplitude/2 + slope*(st-(7*duty/8));
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end
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end
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end
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end |