private void fm_demodulate2(Int32[] dat, string wavefilename, TimeStampLog log)
{
double[] arctans = new double[dat.Length];
for (var i = 0; i < dat.Length; i++)
{
arctans[i] = (double)dat[i] / (double)(1 << 29); // 48kHz (cutoff 15kHz)
}
log.start();
double[] arctans5 = arctans;
// double[] arctans5 = de_emphasis(arctans, 0.67523190665); // fc = 3kHz/48kHz = 0.0625, e^(-2pi*0.0625)
log.stop("FIR: ");
FileStream fs = new FileStream(wavefilename, FileMode.CreateNew);
BinaryWriter bw = new BinaryWriter(fs, Encoding.ASCII);
write_wave_header(bw, (uint)arctans5.Length * 2);
double maxAmp = 0.0;
for (var i = 0; i < arctans5.Length; i++)
{
double val = Math.Abs(arctans5[i]);
if (maxAmp < val)
{
maxAmp = val;
}
}
for (var i = 0; i < arctans5.Length; i++)
{
double v = arctans5[i];
int val = (int)((v / maxAmp) * (1 << 15) + (1 << 12));
short vv = (val > 0x7FFF) ? (short)0x7FFF :
(val < -0x8000) ? (short)-0x8000 : (short)val;
bw.Write(vv);
}
// MessageBox.Show("maxAmp = " + maxAmp);
bw.Close();
fs.Close();
}
private void button_fm_after_demod_Click(object sender, EventArgs e)
{
string msg = "";
OpenFileDialog dlg = new OpenFileDialog();
if (DialogResult.OK == dlg.ShowDialog())
{
TimeStampLog log = new TimeStampLog();
log.start();
Int32[] dat;
read_atan_data_file(dlg.FileName, out dat);
log.stop("Read File: ");
fm_demodulate3(dat, dlg.FileName + ".wav", log);
string[] buf = log.getLog();
for (var i = 0; i < buf.Length; i++)
{
msg += buf[i] + "\n";
}
MessageBox.Show(msg);
}
}
private void button_fm_Click(object sender, EventArgs e)
{
string msg = "";
double fm_tune_freq = Convert.ToDouble(textBox_fm_freq.Text) * 1.0e+6;
OpenFileDialog dlg = new OpenFileDialog();
if (DialogResult.OK == dlg.ShowDialog())
{
TimeStampLog log = new TimeStampLog();
log.start();
Int16[] dat = read_data_file(dlg.FileName);
log.stop("Read File: ");
fm_demodulate(fm_tune_freq, dat, dlg.FileName + ".wav", log);
string[] buf = log.getLog();
for (var i = 0; i < buf.Length; i++)
{
msg += buf[i] + "\n";
}
MessageBox.Show(msg);
}
}
private void fm_demodulate(double tune_freq, Int16[] dat, string wavefilename, TimeStampLog log)
{
Int32[] i_dat = new Int32[dat.Length];
Int32[] q_dat = new Int32[dat.Length];
int rem = (int)(tune_freq / SAMPLE_FREQ);
tune_freq = tune_freq - SAMPLE_FREQ * rem; // TODO: correctly calculate frequency aliasing
log.start();
mixer((int)tune_freq, dat, i_dat, q_dat);
log.stop("mixer: ");
log.start();
// 40MHz -> (CIC 1/32) -> 1.25MHz -> (FIR 2/5) -> 500kHz ->
// (FIR 2/5 cutoff 80kHz:0.08) -> 200kHz -> (FIR 3/5 cutoff 48kHz:0.08) -> 120kHz -> (FIR 2/5 cutoff 15kHz:0.0625) -> 48kHz
double[] i_cic = cic(i_dat, 3, 32);
double[] q_cic = cic(q_dat, 3, 32); // 1.25MHz
log.stop("cic: ");
log.start();
double[] i_fir1 = fir(i_cic, 2, 5, fir_coef_255tap_008); // 500kHz (cutoff 200kHz)
double[] q_fir1 = fir(q_cic, 2, 5, fir_coef_255tap_008);
// FM demodulation
double[] arctans = fm_demodulate_sub(i_fir1, q_fir1);
double[] arctans2 = fir(arctans, 2, 5, fir_coef_255tap_008); // 200kHz (cutoff 80kHz)
double[] arctans3 = fir(arctans2, 3, 5, fir_coef_255tap_008); // 120kHz (cutoff 48kHz)
double[] arctans4 = fir(arctans3, 2, 5, fir_coef_255tap_0625); // 48kHz (cutoff 15kHz)
double[] arctans5 = de_emphasis(arctans4, 0.67523190665); // fc = 3kHz/48kHz = 0.0625, e^(-2pi*0.0625)
log.stop("FIR: ");
FileStream fs = new FileStream(wavefilename, FileMode.CreateNew);
BinaryWriter bw = new BinaryWriter(fs, Encoding.ASCII);
write_wave_header(bw, (uint)arctans5.Length * 2);
double maxAmp = 0.0;
for (var i = 0; i < arctans5.Length; i++)
{
double val = Math.Abs(arctans5[i]);
if (maxAmp < val)
{
maxAmp = val;
}
}
for (var i = 0; i < arctans5.Length; i++)
{
double v = arctans5[i];
short val = (short)((v / maxAmp) * (1 << 15) + (1 << 14));
bw.Write(val);
}
bw.Close();
fs.Close();
}