Bugfix + added meteor demodulator

2026-04-19 14:52:43 +00:00 · 2021-04-01 16:54:16 +02:00
parent bcc1744a76
commit a9cb6bfe79
13 changed files with 789 additions and 31 deletions
--- a/core/src/dsp/window.h
+++ b/core/src/dsp/window.h
@@ -144,4 +144,89 @@ namespace dsp {

        };
    }
+
+
+    class RRCTaps : public filter_window::generic_window {
+        public:
+            RRCTaps() {}
+            RRCTaps(int tapCount, float sampleRate, float baudRate, float alpha) { init(tapCount, sampleRate, baudRate, alpha); }
+
+            void init(int tapCount, float sampleRate, float baudRate, float alpha) {
+                _tapCount = tapCount;
+                _sampleRate = sampleRate;
+                _baudRate = baudRate;
+                _alpha = alpha;
+            }
+
+            int getTapCount() {
+                return _tapCount;
+            }
+
+            void setSampleRate(float sampleRate) {
+                _sampleRate = sampleRate;
+            }
+
+            void setBaudRate(float baudRate) {
+                _baudRate = baudRate;
+            }
+
+            void setTapCount(int count) {
+                _tapCount = count;
+            }
+
+            void setAlpha(float alpha) {
+                _alpha = alpha;
+            }
+
+            void createTaps(float* taps, int tapCount, float factor = 1.0f) {
+                // ======== CREDIT: GNU Radio =========
+                tapCount |= 1; // ensure that tapCount is odd
+
+                double spb = _sampleRate / _baudRate; // samples per bit/symbol
+                double scale = 0;
+                for (int i = 0; i < tapCount; i++)
+                {
+                    double x1, x2, x3, num, den;
+                    double xindx = i - tapCount / 2;
+                    x1 = FL_M_PI * xindx / spb;
+                    x2 = 4 * _alpha * xindx / spb;
+                    x3 = x2 * x2 - 1;
+
+                     // Avoid Rounding errors...
+                    if (fabs(x3) >= 0.000001) {
+                        if (i != tapCount / 2)
+                            num = cos((1 + _alpha) * x1) +
+                                sin((1 - _alpha) * x1) / (4 * _alpha * xindx / spb);
+                        else
+                            num = cos((1 + _alpha) * x1) + (1 - _alpha) * FL_M_PI / (4 * _alpha);
+                        den = x3 * FL_M_PI;
+                    }
+                    else {
+                        if (_alpha == 1)
+                        {
+                            taps[i] = -1;
+                            scale += taps[i];
+                            continue;
+                        }
+                        x3 = (1 - _alpha) * x1;
+                        x2 = (1 + _alpha) * x1;
+                        num = (sin(x2) * (1 + _alpha) * FL_M_PI -
+                            cos(x3) * ((1 - _alpha) * FL_M_PI * spb) / (4 * _alpha * xindx) +
+                            sin(x3) * spb * spb / (4 * _alpha * xindx * xindx));
+                        den = -32 * FL_M_PI * _alpha * _alpha * xindx / spb;
+                    }
+                    taps[i] = 4 * _alpha * num / den;
+                    scale += taps[i];
+                }
+
+                for (int i = 0; i < tapCount; i++) {
+                    taps[i] = taps[i] / scale;
+                }
+            }
+
+        private:
+            int _tapCount;
+            float _sampleRate, _baudRate, _alpha;
+
+        };
 }