From 445af0c0a2174b9718c4258b89dec8f9a1012321 Mon Sep 17 00:00:00 2001 From: Andreas Eversberg Date: Mon, 9 Sep 2019 19:22:43 +0200 Subject: Add filter switch to FSK modulator --- src/bnetz/dialer.c | 2 +- src/bnetz/dsp.c | 2 +- src/libfsk/fsk.c | 27 ++++++++++++++++++++++++--- src/libfsk/fsk.h | 4 +++- src/nmt/dsp.c | 2 +- src/r2000/dsp.c | 4 ++-- 6 files changed, 32 insertions(+), 9 deletions(-) (limited to 'src') diff --git a/src/bnetz/dialer.c b/src/bnetz/dialer.c index e44ddf5..31ef86e 100644 --- a/src/bnetz/dialer.c +++ b/src/bnetz/dialer.c @@ -340,7 +340,7 @@ int main(int argc, char *argv[]) sprintf(funkwahl, "wwww%c%s%se%c%s%se", start_digit, station_id, dialing + 1, start_digit, station_id, dialing + 1); /* init fsk */ - if (fsk_mod_init(&fsk_mod, NULL, fsk_send_bit, samplerate, BIT_RATE, F0, F1, 1.0, 0) < 0) { + if (fsk_mod_init(&fsk_mod, NULL, fsk_send_bit, samplerate, BIT_RATE, F0, F1, 1.0, 0, 0) < 0) { PDEBUG(DDSP, DEBUG_ERROR, "FSK init failed!\n"); goto exit; } diff --git a/src/bnetz/dsp.c b/src/bnetz/dsp.c index e2928ba..7315d26 100644 --- a/src/bnetz/dsp.c +++ b/src/bnetz/dsp.c @@ -96,7 +96,7 @@ int dsp_init_sender(bnetz_t *bnetz, double squelch_db) PDEBUG(DDSP, DEBUG_DEBUG, "Using FSK level of %.3f (%.3f KHz deviation @ 2000 Hz)\n", TX_PEAK_FSK, 4.0); /* init fsk */ - if (fsk_mod_init(&bnetz->fsk_mod, bnetz, fsk_send_bit, bnetz->sender.samplerate, BIT_RATE, F0, F1, TX_PEAK_FSK, 0) < 0) { + if (fsk_mod_init(&bnetz->fsk_mod, bnetz, fsk_send_bit, bnetz->sender.samplerate, BIT_RATE, F0, F1, TX_PEAK_FSK, 0, 0) < 0) { PDEBUG_CHAN(DDSP, DEBUG_ERROR, "FSK init failed!\n"); return -EINVAL; } diff --git a/src/libfsk/fsk.c b/src/libfsk/fsk.c index 7f1ed6e..7026953 100644 --- a/src/libfsk/fsk.c +++ b/src/libfsk/fsk.c @@ -39,7 +39,7 @@ * level = level to modulate the frequencies * coherent = use coherent modulation (FFSK) */ -int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int samplerate, double bitrate, double f0, double f1, double level, int coherent) +int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int samplerate, double bitrate, double f0, double f1, double level, int coherent, int filter) { int i; int rc; @@ -76,9 +76,9 @@ int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int sa PDEBUG(DDSP, DEBUG_DEBUG, "Bitduration of %.4f bits per sample @ %d.\n", fsk->bits_per_sample, samplerate); fsk->phaseshift65536[0] = f0 / (double)samplerate * 65536.0; - PDEBUG(DDSP, DEBUG_DEBUG, "phaseshift65536[0] = %.4f\n", fsk->phaseshift65536[0]); + PDEBUG(DDSP, DEBUG_DEBUG, "F0 = %.0f Hz (phaseshift65536[0] = %.4f)\n", f0, fsk->phaseshift65536[0]); fsk->phaseshift65536[1] = f1 / (double)samplerate * 65536.0; - PDEBUG(DDSP, DEBUG_DEBUG, "phaseshift65536[1] = %.4f\n", fsk->phaseshift65536[1]); + PDEBUG(DDSP, DEBUG_DEBUG, "F1 = %.0f Hz (phaseshift65536[1] = %.4f)\n", f1, fsk->phaseshift65536[1]); /* use coherent modulation, i.e. each bit has an integer number of * half waves and starts/ends at zero crossing @@ -86,6 +86,7 @@ int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int sa if (coherent) { double waves; + PDEBUG(DDSP, DEBUG_DEBUG, "enable coherent FSK modulation mode\n"); fsk->coherent = 1; waves = (f0 / bitrate); if (fabs(round(waves * 2) - (waves * 2)) > 0.001) { @@ -101,6 +102,20 @@ int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int sa fsk->cycles_per_bit65536[1] = waves * 65536.0; } + /* if filter is enabled, add a band pass filter to smoot the spectrum of the tones + * the bandwidth is twice the difference between f0 and f1 + */ + if (filter) { + double low = (f0 + f1) / 2.0 - fabs(f0 - f1); + double high = (f0 + f1) / 2.0 + fabs(f0 - f1); + + PDEBUG(DDSP, DEBUG_DEBUG, "enable filter to smooth FSK transmission. (frequency rage %.0f .. %.0f)\n", low, high); + fsk->filter = 1; + /* use fourth order (2 iter) filter, since it is as fast as second order (1 iter) filter */ + iir_highpass_init(&fsk->lp[0], low, samplerate, 2); + iir_lowpass_init(&fsk->lp[1], high, samplerate, 2); + } + return 0; error: @@ -180,6 +195,12 @@ next_bit: goto next_bit; } + /* post filter */ + if (fsk->filter) { + iir_process(&fsk->lp[0], sample, length); + iir_process(&fsk->lp[1], sample, length); + } + done: fsk->tx_phase65536 = phase; diff --git a/src/libfsk/fsk.h b/src/libfsk/fsk.h index 395e915..4ea8b88 100644 --- a/src/libfsk/fsk.h +++ b/src/libfsk/fsk.h @@ -15,6 +15,8 @@ typedef struct fsk_mod { int low_bit, high_bit; /* a low or high deviation means which bit? */ int tx_bit; /* current transmitting bit (-1 if not set) */ double tx_bitpos; /* current transmit position in bit */ + int filter; /* set, if filters are used */ + iir_filter_t lp[2]; /* filter to smoot transmission spectrum */ } fsk_mod_t; typedef struct fsk_demod { @@ -30,7 +32,7 @@ typedef struct fsk_demod { double rx_bitadjust; /* how much does a bit change cause the sample clock to be adjusted in phase */ } fsk_demod_t; -int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int samplerate, double bitrate, double f0, double f1, double level, int coherent); +int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int samplerate, double bitrate, double f0, double f1, double level, int coherent, int filter); void fsk_mod_cleanup(fsk_mod_t *fsk); int fsk_mod_send(fsk_mod_t *fsk, sample_t *sample, int length, int add); void fsk_mod_tx_reset(fsk_mod_t *fsk); diff --git a/src/nmt/dsp.c b/src/nmt/dsp.c index 1dcd606..d8e1077 100644 --- a/src/nmt/dsp.c +++ b/src/nmt/dsp.c @@ -120,7 +120,7 @@ int dsp_init_sender(nmt_t *nmt, double deviation_factor) PDEBUG(DDSP, DEBUG_DEBUG, "Using Supervisory level of %.3f (%.3f KHz deviation @ 4015 Hz)\n", TX_PEAK_SUPER * deviation_factor, 0.3 * deviation_factor); /* init fsk */ - if (fsk_mod_init(&nmt->fsk_mod, nmt, fsk_send_bit, nmt->sender.samplerate, BIT_RATE, F0, F1, TX_PEAK_FSK, 1) < 0) { + if (fsk_mod_init(&nmt->fsk_mod, nmt, fsk_send_bit, nmt->sender.samplerate, BIT_RATE, F0, F1, TX_PEAK_FSK, 1, 0) < 0) { PDEBUG_CHAN(DDSP, DEBUG_ERROR, "FSK init failed!\n"); return -EINVAL; } diff --git a/src/r2000/dsp.c b/src/r2000/dsp.c index d52e8eb..771089c 100644 --- a/src/r2000/dsp.c +++ b/src/r2000/dsp.c @@ -85,7 +85,7 @@ int dsp_init_sender(r2000_t *r2000) PDEBUG(DDSP, DEBUG_DEBUG, "Using FSK level of %.3f\n", TX_PEAK_FSK); /* init fsk */ - if (fsk_mod_init(&r2000->fsk_mod, r2000, fsk_send_bit, r2000->sender.samplerate, FSK_BIT_RATE, FSK_F0, FSK_F1, TX_PEAK_FSK, 1) < 0) { + if (fsk_mod_init(&r2000->fsk_mod, r2000, fsk_send_bit, r2000->sender.samplerate, FSK_BIT_RATE, FSK_F0, FSK_F1, TX_PEAK_FSK, 1, 0) < 0) { PDEBUG_CHAN(DDSP, DEBUG_ERROR, "FSK init failed!\n"); return -EINVAL; } @@ -99,7 +99,7 @@ int dsp_init_sender(r2000_t *r2000) r2000->rx_max = 144; /* init supervisorty fsk */ - if (fsk_mod_init(&r2000->super_fsk_mod, r2000, super_send_bit, r2000->sender.samplerate, SUPER_BIT_RATE, SUPER_F0, SUPER_F1, TX_PEAK_SUPER, 0) < 0) { + if (fsk_mod_init(&r2000->super_fsk_mod, r2000, super_send_bit, r2000->sender.samplerate, SUPER_BIT_RATE, SUPER_F0, SUPER_F1, TX_PEAK_SUPER, 0, 0) < 0) { PDEBUG_CHAN(DDSP, DEBUG_ERROR, "FSK init failed!\n"); return -EINVAL; } -- cgit v1.2.3