add VOR receiver module

2026-04-20 15:22:42 +00:00 · 2025-01-28 05:07:23 +01:00
parent ea3675da47
commit 4799d0e3a8
8 changed files with 2366 additions and 0 deletions
--- a/decoder_modules/vor_receiver/src/vor_receiver.h
+++ b/decoder_modules/vor_receiver/src/vor_receiver.h
@@ -0,0 +1,106 @@
+#include <dsp/sink.h>
+#include <dsp/types.h>
+#include <dsp/demod/am.h>
+#include <dsp/demod/quadrature.h>
+#include <dsp/convert/real_to_complex.h>
+#include <dsp/channel/frequency_xlator.h>
+#include <dsp/filter/fir.h>
+#include <dsp/math/delay.h>
+#include <dsp/math/conjugate.h>
+#include <dsp/channel/rx_vfo.h>
+#include "vor_fm_filter.h"
+#include <utils/wav.h>
+
+#define VOR_IN_SR   25e3
+
+namespace vor {
+    class Receiver : public dsp::Processor<dsp::complex_t, float> {
+        using base_type = dsp::Processor<dsp::complex_t, float>;
+    public:
+        Receiver() {}
+
+        Receiver(dsp::stream<dsp::complex_t>* in) { init(in); }
+
+        ~Receiver() {
+            if (!base_type::_block_init) { return; }
+            base_type::stop();
+            dsp::taps::free(fmfTaps);
+        }
+
+        void init(dsp::stream<dsp::complex_t>* in) {
+            amd.init(NULL, dsp::demod::AM<float>::CARRIER, VOR_IN_SR, 50.0f / VOR_IN_SR, 5.0f / VOR_IN_SR, 100.0f / VOR_IN_SR, VOR_IN_SR);
+            amr2c.init(NULL);
+            fmr2c.init(NULL);
+            fmx.init(NULL, -9960, VOR_IN_SR);
+            fmfTaps = dsp::taps::fromArray(FM_TAPS_COUNT, fm_taps);
+            fmf.init(NULL, fmfTaps);
+            fmd.init(NULL, 600, VOR_IN_SR);
+            amde.init(NULL, FM_TAPS_COUNT / 2);
+            amv.init(NULL, VOR_IN_SR, 1000, 30, 30);
+            fmv.init(NULL, VOR_IN_SR, 1000, 30, 30);
+
+            base_type::init(in);
+        }
+        
+        int process(dsp::complex_t* in, float* out, int count) {
+            // Demodulate the AM outer modulation
+            volk_32fc_magnitude_32f(amd.out.writeBuf, (lv_32fc_t*)in, count);
+            amr2c.process(count, amd.out.writeBuf, amr2c.out.writeBuf);
+
+            // Isolate the FM subcarrier
+            fmx.process(count, amr2c.out.writeBuf, fmx.out.writeBuf);
+            fmf.process(count, fmx.out.writeBuf, fmx.out.writeBuf);
+
+            // Demodulate the FM subcarrier
+            fmd.process(count, fmx.out.writeBuf, fmd.out.writeBuf);
+            fmr2c.process(count, fmd.out.writeBuf, fmr2c.out.writeBuf);
+
+            // Delay the AM signal by the same amount as the FM one
+            amde.process(count, amr2c.out.writeBuf, amr2c.out.writeBuf);
+
+            // Isolate the 30Hz component on both the AM and FM channels
+            int rcount = amv.process(count, amr2c.out.writeBuf, amv.out.writeBuf);
+            fmv.process(count, fmr2c.out.writeBuf, fmv.out.writeBuf);
+
+            // If no data was returned, we're done for this round
+            if (!rcount) { return 0; }
+
+            // Conjugate FM reference
+            volk_32fc_conjugate_32fc((lv_32fc_t*)fmv.out.writeBuf, (lv_32fc_t*)fmv.out.writeBuf, rcount);
+
+            // Multiply both together
+            volk_32fc_x2_multiply_32fc((lv_32fc_t*)amv.out.writeBuf, (lv_32fc_t*)amv.out.writeBuf, (lv_32fc_t*)fmv.out.writeBuf, rcount);
+            
+            // Compute angle
+            volk_32fc_s32f_atan2_32f(out, (lv_32fc_t*)amv.out.writeBuf, 1.0f, rcount);
+
+            return rcount;
+        }
+
+        int run() {
+            int count = base_type::_in->read();
+            if (count < 0) { return -1; }
+
+            int outCount = process(base_type::_in->readBuf, base_type::out.writeBuf, count);
+
+            // Swap if some data was generated
+            base_type::_in->flush();
+            if (outCount) {
+                if (!base_type::out.swap(outCount)) { return -1; }
+            }
+            return outCount;
+        }
+
+    private:
+        dsp::demod::AM<float> amd;
+        dsp::convert::RealToComplex amr2c;
+        dsp::convert::RealToComplex fmr2c;
+        dsp::channel::FrequencyXlator fmx;
+        dsp::tap<float> fmfTaps;
+        dsp::filter::FIR<dsp::complex_t, float> fmf;
+        dsp::demod::Quadrature fmd;
+        dsp::math::Delay<dsp::complex_t> amde;
+        dsp::channel::RxVFO amv;
+        dsp::channel::RxVFO fmv;
+    };
+}