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AIS: Doesn't use RRC filter -- use rect instead.

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This commit is contained in:
Jared Boone 2016-08-29 20:26:39 -07:00
parent e2fe4b65d9
commit f0c4b0fc98
2 changed files with 8 additions and 16 deletions
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2
firmware/baseband/proc_ais.hpp
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@ -62,7 +62,7 @@ private:
dsp::decimate::FIRC8xR16x24FS4Decim8 decim_0;
dsp::decimate::FIRC16xR16x32Decim8 decim_1;
dsp::matched_filter::MatchedFilter mf { baseband::ais::rrc_taps_38k4_4t_p, 2 };
dsp::matched_filter::MatchedFilter mf { baseband::ais::square_taps_38k4_1t_p, 2 };
clock_recovery::ClockRecovery<clock_recovery::FixedErrorFilter> clock_recovery {
19200, 9600, { 0.0555f },

22
firmware/common/ais_baseband.hpp
View File

@ -32,21 +32,13 @@
namespace baseband {
namespace ais {
// RRC length should be about 4 x the symbol length (4T) to do a good job of
// cleaning up ISI.
// Translate+RRC filter
// sample=38.4k, deviation=2400, b=0.5, symbol=9600
// Length: 16 taps, 4 symbols, 1 cycles of sinusoid
constexpr std::array<std::complex<float>, 16> rrc_taps_38k4_4t_p { {
{ 1.0619794019e-02f, 0.0000000000e+00f }, { 3.5758705854e-03f, 1.4811740938e-03f },
{ -1.3274742629e-02f, -1.3274742629e-02f }, { -1.5018657262e-02f, -3.6258246051e-02f },
{ 0.0000000000e+00f, -2.6549484581e-02f }, { -1.5018657262e-02f, 3.6258246051e-02f },
{ -1.0237997393e-01f, 1.0237997393e-01f }, { -2.2527985355e-01f, 9.3313970669e-02f },
{ -2.8440842032e-01f, 0.0000000000e+00f }, { -2.2527985355e-01f, -9.3313970669e-02f },
{ -1.0237997393e-01f, -1.0237997393e-01f }, { -1.5018657262e-02f, -3.6258246051e-02f },
{ 0.0000000000e+00f, 2.6549484581e-02f }, { -1.5018657262e-02f, 3.6258246051e-02f },
{ -1.3274742629e-02f, 1.3274742629e-02f }, { 3.5758705854e-03f, -1.4811740938e-03f },
// Translate+Rectangular window filter
// sample=38.4k, deviation=2400, symbol=9600
// Length: 4 taps, 1 symbol, 1/4 cycle of sinusoid
// Gain: 1.0 (sinusoid / len(taps))
constexpr std::array<std::complex<float>, 4> square_taps_38k4_1t_p { {
{ 0.25000000f, 0.00000000f }, { 0.23096988f, 0.09567086f },
{ 0.17677670f, 0.17677670f }, { 0.09567086f, 0.23096988f },
} };
} /* namespace ais */