jdsca tests

2026-07-29 15:59:14 +02:00 · 2026-07-11 22:07:33 +02:00
parent bcd9468770
commit 8a4cbb9b5f
3 changed files with 140 additions and 2 deletions
@@ -0,0 +1,66 @@
+#include "qpsk.h"
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+
+#define OQPSK_RRC_DELAY 6 // filter delay in symbols (liquid's "m" param)
+
+static void oqpsk_next_dibit(OQPSKMod *m, float *i, float *q) {
+	uint8_t b0 = m->last_bits[0], b1 = m->last_bits[1], bit;
+	if (bit_ring_read1(m->bitring, &bit)) b0 = bit;
+	if (bit_ring_read1(m->bitring, &bit)) b1 = bit;
+	m->last_bits[0] = b0;
+	m->last_bits[1] = b1;
+	*i = b0 ? -1.0f : 1.0f;
+	*q = b1 ? -1.0f : 1.0f;
+}
+
+void oqpsk_init(OQPSKMod *m, float if_freq, float sample_rate, float symbol_rate, float alpha, bit_ring_t *bitring) {
+	memset(m, 0, sizeof(*m));
+	init_oscillator(&m->carrier, if_freq, sample_rate);
+
+	m->sps = (int)roundf(sample_rate / symbol_rate);
+	if (m->sps < 2) m->sps = 2;
+	if (m->sps % 2 != 0) m->sps += 1; // must be even for the half-symbol Q delay
+
+	m->fir_i = firfilt_rrrf_create_rnyquist(LIQUID_FIRFILT_RRC, m->sps, OQPSK_RRC_DELAY, alpha, 0.0f);
+	m->fir_q = firfilt_rrrf_create_rnyquist(LIQUID_FIRFILT_RRC, m->sps, OQPSK_RRC_DELAY, alpha, 0.0f);
+
+	m->q_delay_len = m->sps / 2;
+	m->q_delay = calloc(m->q_delay_len, sizeof(float));
+	m->q_delay_pos = 0;
+	m->symbol_clock = 0;
+	m->sym_i = m->sym_q = 1.0f;
+	m->bitring = bitring;
+}
+
+float oqpsk_process(OQPSKMod *m) {
+	float impulse_i = 0.0f, impulse_q = 0.0f;
+
+	if (m->symbol_clock == 0) {
+		oqpsk_next_dibit(m, &m->sym_i, &m->sym_q);
+		impulse_i = m->sym_i * (float)m->sps;
+		impulse_q = m->sym_q * (float)m->sps;
+	}
+	m->symbol_clock = (m->symbol_clock + 1) % m->sps;
+
+	float filt_i, filt_q_raw;
+	firfilt_rrrf_push(m->fir_i, impulse_i);
+	firfilt_rrrf_execute(m->fir_i, &filt_i);
+	firfilt_rrrf_push(m->fir_q, impulse_q);
+	firfilt_rrrf_execute(m->fir_q, &filt_q_raw);
+
+	float filt_q = m->q_delay[m->q_delay_pos];
+	m->q_delay[m->q_delay_pos] = filt_q_raw;
+	m->q_delay_pos = (m->q_delay_pos + 1) % m->q_delay_len;
+
+	float c = get_oscillator_cos_sample(&m->carrier);
+	float s = get_oscillator_sin_sample(&m->carrier);
+	return filt_i * c - filt_q * s;
+}
+
+void oqpsk_destroy(OQPSKMod *m) {
+	firfilt_rrrf_destroy(m->fir_i);
+	firfilt_rrrf_destroy(m->fir_q);
+	free(m->q_delay);
+}
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <liquid/liquid.h>
+#include "oscillator.h"
+#include "bit_ring.h"
+
+typedef struct {
+	Oscillator    carrier;        // IF carrier (e.g. 3 kHz)
+	firfilt_rrrf  fir_i, fir_q;   // liquid RRC matched-filter shapers
+	float        *q_delay;
+	int           q_delay_len;
+	int           q_delay_pos;
+	int           sps;            // samples per symbol
+	int           symbol_clock;
+	float         sym_i, sym_q;
+	bit_ring_t   *bitring;
+	uint8_t       last_bits[2];   // hold last symbol if bitring runs dry
+} OQPSKMod;
+
+void  oqpsk_init(OQPSKMod *m, float if_freq, float sample_rate, float symbol_rate, float alpha, bit_ring_t *bitring);
+float oqpsk_process(OQPSKMod *m);
+void  oqpsk_destroy(OQPSKMod *m);