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Final opt. AM-9K, applied to Audio_RX and Mic App.

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Brumi-2021
2022-11-19 18:17:54 +01:00
parent 25dfa96257
commit 1e4c93b979
6 changed files with 63 additions and 55 deletions
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62
firmware/common/dsp_fir_taps.hpp
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@@ -247,20 +247,20 @@ constexpr fir_taps_real<32> taps_6k0_decim_2 {
} },
};
// IFIR prototype filter fs=48000 ; pass=4500 , stop=7800, decim=4, fout=12000
// For Europe AM commercial broadcasting stations in LF/MF/HF, Emissions Designator 9K00A3E Bandwidth: 9.00 kHz (derivated from taps_6k0_decim_2 ):
// Pre-decimate LPF FIR filter design Created by SciPy Python with the "window method", num_taps = 32, cut_off = 4950. sample_rate = 48000 # Hz,
// Created with h = signal.firwin(num_taps, cut_off, nyq=sample_rate/2, window=('chebwin',49)) , achieving good STOP band plot < -60 dB's with some ripple.
// post-escaled h taps to avoid decimals , targetting <= similar int values as previous taps_6k0_dsb_channel peak < 32.767 (2 exp 15) and similar H(f)gain
// IFIR prototype filter fs=48000 ; pass=4500 (cutt off -3dBs) , stop=8000 (<-60dBs), decim=4, fout=12000
// For Europe AM commercial broadcasting stations in LF/MF/HF, Emissions Designator 9K00A3E Bandwidth: 9.00 kHz (derivated from taps_6k0_decim_2 )
// Pre-decimate LPF FIR filter design Created with SciPy Python with the "window method", num_taps = 32, cut_off = 5150. sample_rate = 48000 # Hz,
// Created with h = signal.firwin(num_taps, cut_off, nyq=sample_rate/2, window=('chebwin',50)) , achieving good STOP band plot < -60 dB's with some ripple.
// post-scaled h taps to avoid decimals , targeting <= similar int values as previous taps_6k0_dsb_channel peak < 32.767 (2 exp 15) and similar H(f)gain
constexpr fir_taps_real<32> taps_9k0_decim_2 {
.low_frequency_normalized = -4500.0f / 48000.0f, // Negative -cutt off freq -3dB (real achieved data ,in the plot and measurements)
.high_frequency_normalized = 4500.0f / 48000.0f, // Positive +cutt off freq -3dB (idem)
.transition_normalized = 3300.0f / 48000.0f, // 3300 Hz = (7800 Hz - 4500 Hz) (both from plot H(f) curve plot)
.transition_normalized = 3500.0f / 48000.0f, // 3500 Hz = (8000 Hz - 4500 Hz) (both from plot H(f) curve plot)
.taps = { {
-40, 3, 98, 239, 340, 266, -96, -726,
-1391, -1659, -1041, 772, 3691, 7156, 10271, 12118,
12118, 10271, 7156, 3691, 772, -1041, -1659, -1391,
-726, -96, 266, 340, 239, 98, 3, -40
-53, -30, 47, 198, 355, 372, 89, -535,
-1307, -1771, -1353, 370, 3384, 7109, 10535, 12591,
12591, 10535, 7109, 3384, 370, -1353, -1771, -1307,
-535, 89, 372, 355, 198, 47, -30, -53
} },
};
@@ -292,32 +292,32 @@ constexpr fir_taps_complex<64> taps_6k0_dsb_channel {
} },
};
// Channel filter: fs=12000, pass=4450, stop=4800, decim=1, fout=12000 (4k45 selected = aprox 4k5, after several iterative plot H(f) test, best trade off curve)
// Channel filter: fs=12000, pass=4500 (cutt off -3dBs), stop=4940 (<-60dBs), decim=1, fout=12000 (*1) real frec pass / stop , based on plotted H(f) curve)
// For Europe AM commercial broadcasting stations in LF/MF/HF, Emissions Designator 9K00A3E Bandwidth: 9.00 kHz (derivative from taps_6k0_dsb_channel)
// FIR filter design created by SciPy Python with the "window method"; num_taps = 64, cut_off = 4450. sample_rate = 12000 # Hz,
// Created with : h=signal.firwin(num_taps, cut_off, nyq=sample_rate/2, window=('chebwin',50)), achieving good STOP band plot < -60 dB's with some ripple.
// post-escaled h taps to avoid decimals , targetting <= similar int values as previous taps_6k0_dsb_channel peak < 32.767 (2 exp 15), (29253) and similar H(f)gain
// FIR filter design created with SciPy Python using "window method"; selected design parameters: num_taps = 64, cut_off = 4575. sample_rate = 12000 # Hz,
// Created with : h = signal.firwin(num_taps, cut_off, nyq=sample_rate/2, window=('chebwin',50)) , achieving real plot curve (*1) with peak stop band ripple -60dBs.
// post-scaled h taps to avoid decimals , targeting <= similar int values as previous taps_6k0_dsb_channel peak < 32.767 (2 exp 15), (29625) and similar H(f)gain
constexpr fir_taps_complex<64> taps_9k0_dsb_channel {
.low_frequency_normalized = -4500.0f / 12000.0f, // Negative -cutt off freq -3dB (in the H(f) curve plot)
.high_frequency_normalized = 4500.0f / 12000.0f, // Positive +cutt off freq -3dB (in the H(f) curve plot)
.transition_normalized = 350.0f / 12000.0f, // 350Hz = (4800 Hz -4450 Hz) cut-3dB's (both data comes from H(f) curve plot and confirmed by measurements )
.transition_normalized = 440.0f / 12000.0f, // 440Hz = (4940 Hz -4500 Hz) cut-3dB's (both data comes from H(f) curve plot and confirmed by measurements )
.taps = { {
{ -34, 0 }, { 23, 0 }, { -13, 0 }, { -19, 0 },
{ 55, 0 }, { -65, 0 }, { 25, 0 }, { 59, 0 },
{ -137, 0 }, { 141, 0 }, { -35, 0 }, { -146, 0 },
{ 287, 0 }, { -262, 0 }, { 26, 0 }, { 317, 0 },
{ -544, 0 }, { 441, 0 }, { 29, 0 }, { -638, 0 },
{ 980, 0 }, { -707, 0 }, { -191, 0 }, { 1272, 0 },
{ -1805, 0 }, { 1175, 0 }, { 660, 0 }, { -2934, 0 },
{ 4214, 0 }, { -2774, 0 }, { -3655, 0 }, { 29253, 0 },
{ 29253, 0 }, { -3655, 0 }, { -2774, 0 }, { 4214, 0 },
{ -2934, 0 }, { 660, 0 }, { 1175, 0 }, { -1805, 0 },
{ 1272, 0 }, { -191, 0 }, { -707, 0 }, { 980, 0 },
{ -638, 0 }, { 29, 0 }, { 441, 0 }, { -544, 0 },
{ 317, 0 }, { 26, 0 }, { -262, 0 }, { 287, 0 },
{ -146, 0 }, { -35, 0 }, { 141, 0 }, { -137, 0 },
{ 59, 0 }, { 25, 0 }, { -65, 0 }, { 55, 0 },
{ -19, 0 }, { -13, 0 }, { 23, 0 }, { -34, 0 },
{ 2, 0 }, { -18, 0 }, { 34, 0 }, { -33, 0 },
{ 6, 0 }, { 44, 0 }, { -91, 0 }, { 96, 0 },
{ -35, 0 }, { -80, 0 }, { 193, 0 }, { -223, 0 },
{ 116, 0 }, { 112, 0 }, { -353, 0 }, { 452, 0 },
{ -293, 0 }, { -111, 0 }, { 584, 0 }, { -844, 0 },
{ 653, 0 }, { 22, 0 }, { -921, 0 }, { 1554, 0 },
{ -1422, 0 }, { 301, 0 }, { 1533, 0 }, { -3282, 0 },
{ 3804, 0 }, { -1819, 0 }, { -4605, 0 }, { 29625, 0 },
{ 29625, 0 }, { -4605, 0 }, { -1819, 0 }, { 3804, 0 },
{ -3282, 0 }, { 1533, 0 }, { 301, 0 }, { -1422, 0 },
{ 1554, 0 }, { -921, 0 }, { 22, 0 }, { 653, 0 },
{ -844, 0 }, { 584, 0 }, { -111, 0 }, { -293, 0 },
{ 452, 0 }, { -353, 0 }, { 112, 0 }, { 116, 0 },
{ -223, 0 }, { 193, 0 }, { -80, 0 }, { -35, 0 },
{ 96, 0 }, { -91, 0 }, { 44, 0 }, { 6, 0 },
{ -33, 0 }, { 34, 0 }, { -18, 0 }, { 2, 0 },
} },
};