feat: merge nearby detector fragments across small gaps

internal/config/config.go

@@ -30,6 +30,7 @@ type DetectorConfig struct {
 	CFARWrapAround  bool    `yaml:"cfar_wrap_around" json:"cfar_wrap_around"`
 	EdgeMarginDb    float64 `yaml:"edge_margin_db" json:"edge_margin_db"`
 	MaxSignalBwHz   float64 `yaml:"max_signal_bw_hz" json:"max_signal_bw_hz"`
+	MergeGapHz      float64 `yaml:"merge_gap_hz" json:"merge_gap_hz"`
 
 	// Deprecated (backward compatibility)
 	CFAREnabled *bool `yaml:"cfar_enabled,omitempty" json:"cfar_enabled,omitempty"`
@@ -111,6 +112,7 @@ func Default() Config {
 			CFARWrapAround:  true,
 			EdgeMarginDb:    3.0,
 			MaxSignalBwHz:   150000,
+			MergeGapHz:      5000,
 		},
 		Recorder: RecorderConfig{
 			Enabled:     false,
@@ -197,6 +199,9 @@ func applyDefaults(cfg Config) Config {
 	if cfg.Detector.MaxSignalBwHz <= 0 {
 		cfg.Detector.MaxSignalBwHz = 150000
 	}
+	if cfg.Detector.MergeGapHz <= 0 {
+		cfg.Detector.MergeGapHz = 5000
+	}
 	if cfg.FrameRate <= 0 {
 		cfg.FrameRate = 15
 	}

internal/detector/detector.go

@@ -34,6 +34,7 @@ type Detector struct {
 	CFARScaleDb     float64
 	EdgeMarginDb    float64
 	MaxSignalBwHz   float64
+	MergeGapHz      float64
 	binWidth        float64
 	nbins           int
 	sampleRate      int
@@ -87,6 +88,7 @@ func New(detCfg config.DetectorConfig, sampleRate int, fftSize int) *Detector {
 	thresholdDb := detCfg.ThresholdDb
 	edgeMarginDb := detCfg.EdgeMarginDb
 	maxSignalBwHz := detCfg.MaxSignalBwHz
+	mergeGapHz := detCfg.MergeGapHz
 
 	if minDur <= 0 {
 		minDur = 250 * time.Millisecond
@@ -121,6 +123,9 @@ func New(detCfg config.DetectorConfig, sampleRate int, fftSize int) *Detector {
 	if maxSignalBwHz <= 0 {
 		maxSignalBwHz = 150000
 	}
+	if mergeGapHz <= 0 {
+		mergeGapHz = 5000
+	}
 	if cfarRank <= 0 || cfarRank > 2*cfarTrain {
 		cfarRank = int(math.Round(0.75 * float64(2*cfarTrain)))
 		if cfarRank <= 0 {
@@ -149,6 +154,7 @@ func New(detCfg config.DetectorConfig, sampleRate int, fftSize int) *Detector {
 		CFARScaleDb:     cfarScaleDb,
 		EdgeMarginDb:    edgeMarginDb,
 		MaxSignalBwHz:   maxSignalBwHz,
+		MergeGapHz:      mergeGapHz,
 		binWidth:        float64(sampleRate) / float64(fftSize),
 		nbins:           fftSize,
 		sampleRate:      sampleRate,
@@ -323,6 +329,10 @@ func (d *Detector) mergeOverlapping(signals []Signal, centerHz float64) []Signal
 	if len(signals) <= 1 {
 		return signals
 	}
+	gapBins := 0
+	if d.MergeGapHz > 0 && d.binWidth > 0 {
+		gapBins = int(math.Ceil(d.MergeGapHz / d.binWidth))
+	}
 	sort.Slice(signals, func(i, j int) bool {
 		return signals[i].FirstBin < signals[j].FirstBin
 	})
@@ -330,7 +340,8 @@ func (d *Detector) mergeOverlapping(signals []Signal, centerHz float64) []Signal
 	for i := 1; i < len(signals); i++ {
 		last := &merged[len(merged)-1]
 		cur := signals[i]
-		if cur.FirstBin <= last.LastBin+1 {
+		gap := cur.FirstBin - last.LastBin - 1
+		if gap <= gapBins {
 			if cur.LastBin > last.LastBin {
 				last.LastBin = cur.LastBin
 			}
@@ -343,6 +354,9 @@ func (d *Detector) mergeOverlapping(signals []Signal, centerHz float64) []Signal
 			centerBin := float64(last.FirstBin+last.LastBin) / 2.0
 			last.BWHz = float64(last.LastBin-last.FirstBin+1) * d.binWidth
 			last.CenterHz = d.centerFreqForBin(centerBin, centerHz)
+			if cur.NoiseDb < last.NoiseDb || last.NoiseDb == 0 {
+				last.NoiseDb = cur.NoiseDb
+			}
 		} else {
 			merged = append(merged, cur)
 		}

internal/detector/detector_test.go

@@ -72,6 +72,7 @@ func TestSignalBandwidthExpansion(t *testing.T) {
 		CFARWrapAround:  true,
 		EdgeMarginDb:    3.0,
 		MaxSignalBwHz:   150000,
+		MergeGapHz:      5000,
 	}
 	d := New(cfg, sampleRate, fftSize)
 	spectrum := make([]float64, fftSize)
@@ -101,3 +102,38 @@ func TestSignalBandwidthExpansion(t *testing.T) {
 		t.Errorf("BW too narrow: got %.0f Hz, want >= %.0f Hz (FirstBin=%d LastBin=%d)", sig.BWHz, expectedMinBW, sig.FirstBin, sig.LastBin)
 	}
 }
+
+func TestMergeGap(t *testing.T) {
+	sampleRate := 2048000
+	fftSize := 2048
+	cfg := config.DetectorConfig{
+		ThresholdDb:     -20,
+		MinDurationMs:   1,
+		HoldMs:          10,
+		EmaAlpha:        1.0,
+		HysteresisDb:    3,
+		MinStableFrames: 1,
+		GapToleranceMs:  10,
+		CFARMode:        "OFF",
+		MergeGapHz:      5000,
+	}
+	d := New(cfg, sampleRate, fftSize)
+	spectrum := make([]float64, fftSize)
+	for i := range spectrum {
+		spectrum[i] = -100
+	}
+	for i := 500; i <= 505; i++ {
+		spectrum[i] = -20
+	}
+	for i := 509; i <= 514; i++ {
+		spectrum[i] = -20
+	}
+	now := time.Now()
+	_, signals := d.Process(now, spectrum, 434e6)
+	if len(signals) != 1 {
+		t.Errorf("expected 1 merged signal, got %d", len(signals))
+	}
+	if len(signals) == 1 && signals[0].BWHz < 14000 {
+		t.Errorf("merged BW too narrow: %.0f Hz", signals[0].BWHz)
+	}
+}

internal/runtime/runtime.go

@@ -35,6 +35,7 @@ type DetectorUpdate struct {
 	CFARScaleDb     *float64 `json:"cfar_scale_db"`
 	CFARWrapAround  *bool    `json:"cfar_wrap_around"`
 	EdgeMarginDb    *float64 `json:"edge_margin_db"`
+	MergeGapHz      *float64 `json:"merge_gap_hz"`
 }
 
 type SettingsUpdate struct {
@@ -203,6 +204,13 @@ func (m *Manager) ApplyConfig(update ConfigUpdate) (config.Config, error) {
 			}
 			next.Detector.EdgeMarginDb = v
 		}
+		if update.Detector.MergeGapHz != nil {
+			v := *update.Detector.MergeGapHz
+			if math.IsNaN(v) || math.IsInf(v, 0) || v < 0 {
+				return m.cfg, errors.New("merge_gap_hz must be >= 0")
+			}
+			next.Detector.MergeGapHz = v
+		}
 	}
 	if update.Recorder != nil {
 		if update.Recorder.Enabled != nil {

web/app.js

@@ -43,6 +43,7 @@ const hysteresisInput = qs('hysteresisInput');
 const stableFramesInput = qs('stableFramesInput');
 const gapToleranceInput = qs('gapToleranceInput');
 const edgeMarginInput = qs('edgeMarginInput');
+const mergeGapInput = qs('mergeGapInput');
 const agcToggle = qs('agcToggle');
 const dcToggle = qs('dcToggle');
 const iqToggle = qs('iqToggle');
@@ -420,6 +421,7 @@ function applyConfigToUI(cfg) {
   if (stableFramesInput) stableFramesInput.value = cfg.detector.min_stable_frames ?? 3;
   if (gapToleranceInput) gapToleranceInput.value = cfg.detector.gap_tolerance_ms ?? cfg.detector.hold_ms;
   if (edgeMarginInput) edgeMarginInput.value = cfg.detector.edge_margin_db ?? 3.0;
+  if (mergeGapInput) mergeGapInput.value = cfg.detector.merge_gap_hz ?? 5000;
   agcToggle.checked = !!cfg.agc;
   dcToggle.checked = !!cfg.dc_block;
   iqToggle.checked = !!cfg.iq_balance;
@@ -1422,6 +1424,10 @@ if (edgeMarginInput) edgeMarginInput.addEventListener('change', () => {
   const v = parseFloat(edgeMarginInput.value);
   if (Number.isFinite(v)) queueConfigUpdate({ detector: { edge_margin_db: v } });
 });
+if (mergeGapInput) mergeGapInput.addEventListener('change', () => {
+  const v = parseFloat(mergeGapInput.value);
+  if (Number.isFinite(v)) queueConfigUpdate({ detector: { merge_gap_hz: v } });
+});
 
 agcToggle.addEventListener('change', () => queueSettingsUpdate({ agc: agcToggle.checked }));
 dcToggle.addEventListener('change', () => queueSettingsUpdate({ dc_block: dcToggle.checked }));

web/index.html

@@ -198,6 +198,7 @@
               <label class="field"><span>Min Stable Frames</span><input id="stableFramesInput" type="number" step="1" min="1" /></label>
               <label class="field"><span>Gap Tolerance (ms)</span><input id="gapToleranceInput" type="number" step="50" min="0" /></label>
               <label class="field"><span>Edge Margin (dB)</span><input id="edgeMarginInput" type="number" step="0.5" min="0" /></label>
+              <label class="field"><span>Merge Gap (Hz)</span><input id="mergeGapInput" type="number" step="500" min="0" /></label>
               <label class="field"><span>CFAR Mode</span>
                 <select id="cfarModeSelect">
                   <option value="OFF">Off</option>