internal void MakeFirLowpass(float cutoff_freq,
float samplerate,
WindowType_e type,
ref CPX[] taps,
int length)
{
float[] window = new float[length];
float fc = cutoff_freq / samplerate;
if (fc > 0.5)
{
return;
}
int midpoint = length >> 1;
makewindow(type, length, ref window);
for (int i = 1; i <= length; i++)
{
int j = i - 1;
if (i != midpoint)
{
taps[j].real = (Convert.ToSingle(Math.Sin(TWOPI * (i - midpoint) * fc) / (ONEPI * (i - midpoint)))) * window[j];
taps[j].imaginary = (Convert.ToSingle(Math.Cos(TWOPI * (i - midpoint) * fc) / (ONEPI * (i - midpoint)))) * window[j];
}
else
{
taps[midpoint - 1].real = 2.0F * fc;
taps[midpoint - 1].imaginary = 2.0F * fc;
}
}
}
public OutbandPowerSpectrumSignal(ref DSPBuffer dsp_buffer_obj, WindowType_e filterType)
{
this.d = dsp_buffer_obj;
this.s = d.State;
this.block_size = s.DSPBlockSize;
this.window = new float[s.DSPBlockSize];
this.ps_results = new float[s.DSPBlockSize * 2];
this.ps_average = new float[s.DSPBlockSize * 2];
this.filt_design = new FilterDesigner();
filt_design.makewindow(filterType,
s.DSPBlockSize,
ref window);
this.ps_cpx = new CPX[s.DSPBlockSize * 2];
this.tmp_cpx = new CPX[s.DSPBlockSize * 2];
h_ps = GCHandle.Alloc(ps_cpx, GCHandleType.Pinned);
h_temp = GCHandle.Alloc(tmp_cpx, GCHandleType.Pinned);
// in: tmp_cpx_1 out: ps_cpx
plan_fwd_ps = FFTW.dft_1d(s.DSPBlockSize * 2,
h_temp.AddrOfPinnedObject(),
h_ps.AddrOfPinnedObject(),
FFTW.fftw_direction.Forward,
FFTW.fftw_flags.Measure);
}
public OutbandPowerSpectrumSignal(int nsize, WindowType_e filter)
{
this.block_size = nsize;
this.window = new float[nsize];
this.ps_results = new float[nsize * 2];
this.ps_average = new float[nsize * 2];
this.filt_design = new FilterDesigner();
filt_design.makewindow(filter,
nsize,
ref window);
this.ps_cpx = new CPX[nsize * 2];
this.tmp_cpx = new CPX[nsize * 2];
h_ps = GCHandle.Alloc(ps_cpx, GCHandleType.Pinned);
h_temp = GCHandle.Alloc(tmp_cpx, GCHandleType.Pinned);
// in: tmp_cpx_1 out: ps_cpx
plan_fwd_ps = FFTW.dft_1d(nsize * 2,
h_temp.AddrOfPinnedObject(),
h_ps.AddrOfPinnedObject(),
FFTW.fftw_direction.Forward,
FFTW.fftw_flags.Measure);
}
internal void makewindow(WindowType_e type,
int size,
ref float[] window)
{
int i, j, midn, midp1, midm1;
float freq, rate, sr1, angle, expn, expsum, cx, two_pi;
midn = size / 2;
midp1 = (size + 1) / 2;
midm1 = (size - 1) / 2;
two_pi = 8.0F * (float)Math.Atan(1.0F);
freq = two_pi / (float)size;
rate = 1.0F / (float)midn;
angle = 0.0F;
expn = (float)Math.Log(2.0F) / (float)midn + 1.0F;
expsum = 1.0F;
switch (type)
{
case WindowType_e.RECTANGULAR_WINDOW:
for (i = 0; i < size; i++)
{
window[i] = 1.0F;
}
break;
case WindowType_e.HANNING_WINDOW: /* Hann would be more accurate */
for (i = 0, j = size - 1, angle = 0.0F; i <= midn; i++, j--, angle += freq)
{
window[j] = (window[i] = 0.5F - 0.5F * (float)Math.Cos(angle));
}
break;
case WindowType_e.WELCH_WINDOW:
for (i = 0, j = size - 1; i <= midn; i++, j--)
{
window[j] = (window[i] = 1.0F - (float)Math.Pow((float)((i - midm1) / (float)midp1), 2));
}
break;
case WindowType_e.PARZEN_WINDOW:
for (i = 0, j = size - 1; i <= midn; i++, j--)
{
window[j] = (window[i] = 1.0F - Math.Abs((float)(i - midm1) / (float)midp1));
}
break;
case WindowType_e.BARTLETT_WINDOW:
for (i = 0, j = size - 1, angle = 0.0F; i <= midn; i++, j--, angle += rate)
{
window[j] = (window[i] = angle);
}
break;
case WindowType_e.HAMMING_WINDOW:
for (i = 0, j = size - 1, angle = 0.0F; i <= midn; i++, j--, angle += freq)
{
window[j] = (window[i] = 0.54F - 0.46F * (float)Math.Cos(angle));
}
break;
case WindowType_e.BLACKMAN2_WINDOW: /* using Chebyshev polynomial equivalents here */
for (i = 0, j = size - 1, angle = 0.0F; i <= midn; i++, j--, angle += freq)
{
cx = (float)Math.Cos(angle);
window[j] = (window[i] = (.34401F + (cx * (-.49755F + (cx * .15844F)))));
}
break;
case WindowType_e.BLACKMAN3_WINDOW:
for (i = 0, j = size - 1, angle = 0.0F; i <= midn; i++, j--, angle += freq)
{
cx = (float)Math.Cos(angle);
window[j] =
(window[i] = (.21747F + (cx * (-.45325F + (cx * (.28256F - (cx * .04672F)))))));
}
break;
case WindowType_e.BLACKMAN4_WINDOW:
for (i = 0, j = size - 1, angle = 0.0F; i <= midn; i++, j--, angle += freq)
{
cx = (float)Math.Cos(angle);
window[j] = (window[i] =
(.084037F +
(cx *
(-.29145F +
(cx *
(.375696F + (cx * (-.20762F + (cx * .041194F)))))))));
}
break;
case WindowType_e.EXPONENTIAL_WINDOW:
for (i = 0, j = size - 1; i <= midn; i++, j--)
{
window[j] = (window[i] = expsum - 1.0F);
expsum *= expn;
}
break;
case WindowType_e.RIEMANN_WINDOW:
sr1 = two_pi / (float)size;
for (i = 0, j = size - 1; i <= midn; i++, j--)
{
if (i == midn)
{
window[j] = (window[i] = 1.0F);
}
else
{
/* split out because NeXT C compiler can't handle the full expression */
cx = sr1 * (midn - i);
window[i] = (float)Math.Sin(cx) / cx;
window[j] = window[i];
}
}
break;
case WindowType_e.BLACKMANHARRIS_WINDOW:
{
float
a0 = 0.35875F,
a1 = 0.48829F,
a2 = 0.14128F,
a3 = 0.01168F;
for (i = 0; i < size; i++)
{
window[i] = a0 - a1 * (float)Math.Cos(two_pi * (float)(i + 0.5) / (float)size)
+ a2 * (float)Math.Cos(2.0 * two_pi * (float)(i + 0.5) / (float)size)
- a3 * (float)Math.Cos(3.0 * two_pi * (float)(i + 0.5) / (float)size);
}
}
break;
default:
return;
}
}
