private bool DesignBilinear(double fc, double fs, long sampleFreq, AnalogFilterDesign.FilterType filterType)
{
double twoπ = 2.0 * Math.PI;
mIIRBilinear = new BilinearDesign(fc, sampleFreq);
double fc_pw = mIIRBilinear.PrewarpωtoΩ(twoπ * fc) / twoπ;
double fs_pw = mIIRBilinear.PrewarpωtoΩ(twoπ * fs) / twoπ;
mAfd = new AnalogFilterDesign();
mAfd.DesignLowpass(0, CUTOFF_GAIN_DB, StopbandRippleDb(),
fc_pw, fs_pw,
filterType,
ApproximationBase.BetaType.BetaMax);
// 連続時間伝達関数を離散時間伝達関数に変換。
for (int i = 0; i < mAfd.HPfdCount(); ++i)
{
var s = mAfd.HPfdNth(i);
mIIRBilinear.Add(s);
}
mIIRBilinear.Calc();
return(true);
}
private bool DesignImpulseInvariance(double fc, double fs, long samplingFreq, AnalogFilterDesign.FilterType filterType)
{
mAfd = new AnalogFilterDesign();
mAfd.DesignLowpass(0, CUTOFF_GAIN_DB, StopbandRippleDb(),
fc,
fs,
filterType,
ApproximationBase.BetaType.BetaMax);
var H_s = new List <FirstOrderComplexRationalPolynomial>();
for (int i = 0; i < mAfd.HPfdCount(); ++i)
{
var p = mAfd.HPfdNth(i);
H_s.Add(p);
}
mIIRiim = new ImpulseInvarianceMethod(H_s, fc * 2.0 * Math.PI, samplingFreq, mMethod == Method.ImpulseInvarianceMinimumPhase);
return(true);
}
void CalcFilter(object sender, DoWorkEventArgs e)
{
var r = new BackgroundCalcResult();
e.Result = r;
r.success = false;
r.message = "unknown error";
mAfd = new AnalogFilterDesign();
try {
mAfd.DesignLowpass(mG0, mGc, mGs, mFc, mFs, mFilterType, mBetaType);
r.success = true;
} catch (System.ArgumentOutOfRangeException ex) {
r.message = string.Format("Design failed! {0}", ex);
return;
} catch (System.Exception ex) {
r.message = string.Format("BUG: should be fixed! {0}", ex);
return;
}
}
