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function outputVoltage = helperHarmonicDistortion(inputVoltage)
//helperHarmonicDistortionADC Helper function for HarmonicDistortionExample.m
//Calling Sequence
// outputVoltage=helperHarmonicDistortionAmplifier(inputVoltage)
//Description
//Analizing the harmonic distortion of a weakly non-linear system in the presence of noise.
//Example
//VmaxPk = 2;
//Fi = 2000;
//Fs = 44.1e3;
//Tstop = 50e-3;
//t = 0:1/Fs:Tstop;
//inputVmax = VmaxPk*sin(2*%pi*Fi*t);z
//outputVmax = helperHarmonicDistortionAmplifier(inputVmax);
//plot(t, outputVmax);replot([0,-2.5,0.005,2.5]);
//xlabel('Time')
//ylabel('Output Voltage')
//title('Amplifier output')
// model parameters
noiseVrms = 0.4e-6; // RMS voltage of input noisefloor
// polynomial coefficients
a0 = 25e-3; // dc bias (25mV)
a1 = 1; // voltage gain
a2 = 6e-5; // second order term
a3 = -1e-3; // third order term
a4 = 5e-6; // fourth order term
a5 = 1e-5; // fifth order term
// polyval function has constant term at the end.
polyCoeff = [a5 a4 a3 a2 a1 a0];
// get number of input samples
n = size(inputVoltage,2);
// add noise at input
inputNoise = noiseVrms*rand(1,n,"normal");
distortedInput = inputVoltage + inputNoise;
// adjust input by DC bias, voltage gain and higher order terms
outputVoltage = polyval(polyCoeff, distortedInput);
endfunction
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