public void BandPass()
{
const double lowPassbandFreq = 2500 / _SamplingFrequency;
const double lowStopbandFreq = 2000 / _SamplingFrequency;
const double highPassbandFreq = 3000 / _SamplingFrequency;
const double highStopbandFreq = 3500 / _SamplingFrequency;
const double passbandRipple = 5;
const double stopbandAttenuation = 6;
var(eb, ea) = IirCoefficients.BandPass(lowStopbandFreq, lowPassbandFreq, highPassbandFreq, highStopbandFreq, passbandRipple, stopbandAttenuation);
var b = eb.ToArray();
var a = ea.ToArray();
var desiredB = new double[] { 0.02602409840677345, 0, -0.02602409840677345 };
var desiredA = new double[] { 1, -1.770384034934973, 0.9479518031864529 };
Assert.AreEqual(desiredB.Length, b.Length);
Assert.AreEqual(desiredA.Length, a.Length);
for (int i = 0; i < b.Length; i++)
{
Assert.AreEqual(desiredB[i], b[i], _Tolerance);
}
for (int i = 0; i < a.Length; i++)
{
Assert.AreEqual(desiredA[i], a[i], _Tolerance);
}
}
public void HighPass()
{
const double passbandFreq = 2500 / _SamplingFrequency;
const double stopbandFreq = 2000 / _SamplingFrequency;
const double passbandRipple = 5;
const double stopbandAttenuation = 6;
var(eb, ea) = IirCoefficients.HighPass(stopbandFreq, passbandFreq, passbandRipple, stopbandAttenuation);
var b = eb.ToArray();
var a = ea.ToArray();
var desiredB = new double[] { 0.7736977585189119, -0.7736977585189119 };
var desiredA = new double[] { 1, -0.5473955170378236 };
Assert.AreEqual(desiredB.Length, b.Length);
Assert.AreEqual(desiredA.Length, a.Length);
for (int i = 0; i < b.Length; i++)
{
Assert.AreEqual(desiredB[i], b[i], _Tolerance);
}
for (int i = 0; i < a.Length; i++)
{
Assert.AreEqual(desiredA[i], a[i], _Tolerance);
}
}
public void LowPass()
{
const double passbandFreq = 2000 / _SamplingFrequency;
const double stopbandFreq = 2500 / _SamplingFrequency;
const double passbandRipple = 5;
const double stopbandAttenuation = 6;
var(eb, ea) = IirCoefficients.LowPass(passbandFreq, stopbandFreq, passbandRipple, stopbandAttenuation);
var b = eb.ToArray();
var a = ea.ToArray();
var desiredB = new double[] { 0.09723679451225617, 0.09723679451225617 };
var desiredA = new double[] { 1, -0.8055264109754877 };
Assert.AreEqual(desiredB.Length, b.Length);
Assert.AreEqual(desiredA.Length, a.Length);
for (int i = 0; i < b.Length; i++)
{
Assert.AreEqual(desiredB[i], b[i], _Tolerance);
}
for (int i = 0; i < a.Length; i++)
{
Assert.AreEqual(desiredA[i], a[i], _Tolerance);
}
}
public void BandStop()
{
const double lowPassbandFreq = 2000 / _SamplingFrequency;
const double lowStopbandFreq = 2500 / _SamplingFrequency;
const double highPassbandFreq = 3500 / _SamplingFrequency;
const double highStopbandFreq = 3000 / _SamplingFrequency;
const double passbandRipple = 5;
const double stopbandAttenuation = 6;
var(eb, ea) = IirCoefficients.BandStop(lowPassbandFreq, lowStopbandFreq, highStopbandFreq, highPassbandFreq, passbandRipple, stopbandAttenuation);
var b = eb.ToArray();
var a = ea.ToArray();
var desiredB = new double[] { 0.8634280116150362, -1.569442492959457, 0.8634280116150361 };
var desiredA = new double[] { 1, -1.569442492959457, 0.7268560232300724 };
Assert.AreEqual(desiredB.Length, b.Length);
Assert.AreEqual(desiredA.Length, a.Length);
for (int i = 0; i < b.Length; i++)
{
Assert.AreEqual(desiredB[i], b[i], _Tolerance);
}
for (int i = 0; i < a.Length; i++)
{
Assert.AreEqual(desiredA[i], a[i], _Tolerance);
}
}
/// <summary>
/// Create a filter to remove middle (all but low and high) frequencies in online processing scenarios.
/// </summary>
public static OnlineFilter CreateBandstop(ImpulseResponse mode, double sampleRate, double cutoffLowRate, double cutoffHighRate, int order)
{
if (mode == ImpulseResponse.Finite)
{
double[] c = FirCoefficients.BandStop(sampleRate, cutoffLowRate, cutoffHighRate, order >> 1);
return(new OnlineFirFilter(c));
}
if (mode == ImpulseResponse.Infinite)
{
double[] c = IirCoefficients.BandStop(sampleRate, cutoffLowRate, cutoffHighRate);
return(new OnlineIirFilter(c));
}
throw new ArgumentException("mode");
}
/// <summary>
/// Create a filter to remove low frequencies in online processing scenarios.
/// </summary>
public static OnlineFilter CreateHighpass(ImpulseResponse mode, double sampleRate, double cutoffRate, int order)
{
if (mode == ImpulseResponse.Finite)
{
double[] c = FirCoefficients.HighPass(sampleRate, cutoffRate, order >> 1);
return(new OnlineFirFilter(c));
}
if (mode == ImpulseResponse.Infinite)
{
// TODO: investigate (bandwidth)
double[] c = IirCoefficients.HighPass(sampleRate, cutoffRate, cutoffRate);
return(new OnlineIirFilter(c));
}
throw new ArgumentException("mode");
}
