Averaged noise marker caching and improve LF noise floor with large RBW

nanovna.h

@@ -676,6 +676,7 @@ float get_level_offset(void);
 
 extern uint8_t in_selftest;
 extern int display_test(void);
+extern void clear_marker_cache(void);
 
 //
 // Shell config functions and macros

plot.c

@@ -280,9 +280,20 @@ index_to_value(const int i)
   return(value(actual_t[i]));
 }
 #endif
+
+float marker_cache[MARKERS_MAX];
+bool marker_cache_valid[MARKERS_MAX];
+void
+clear_marker_cache(void)
+{
+  for (int i = 0; i<MARKERS_MAX; i++)
+    marker_cache_valid[i] = false;
+}
 float
 marker_to_value(const int i)
 {
+  if (marker_cache_valid[i])
+    return marker_cache[i];
   float *ref_marker_levels;
   if (markers[i].mtype & M_STORED )
     ref_marker_levels = stored_t;
@@ -290,11 +301,26 @@ marker_to_value(const int i)
     ref_marker_levels = actual_t;
   float v = value(ref_marker_levels[markers[i].index]);
   if (markers[i].mtype & M_AVER) {
+    int old_unit = setting.unit;
+    if (markers[i].mtype & M_NOISE)
+      setting.unit = U_WATT;            // Noise averaging should always be done in Watts
     v = 0;
     for (int i=0; i<sweep_points; i++)
-      v += value(ref_marker_levels[i]);
+      v += value(ref_marker_levels[i]); // TODO this should be power averaging for noise markers
     v /= sweep_points;
+    v = to_dBm(v);
+    setting.unit = old_unit;
+    v = value(v);
+  }
+  if (markers[i].mtype & M_NOISE){
+    v = v - logf(actual_rbw_x10*100.0) * (10.0/logf(10.0))
+#ifdef TINYSA4
+    + SI4463_noise_correction_x10/10.0
+#endif
+    ;
   }
+  marker_cache_valid[i] = true;
+  marker_cache[i] = v;
   return(v);
 }
 
@@ -1444,13 +1470,6 @@ static void trace_print_value_string(     // Only used at one place
 //  if (mtype & M_NOISE)
 //    *ptr2++  = 'N';
   *ptr2++ =  ' ';
-  if (mtype & M_NOISE){
-    v +=   - logf(actual_rbw_x10*100.0) * (10.0/logf(10.0))
-#ifdef TINYSA4
-    + SI4463_noise_correction_x10/10.0
-#endif
-    ;
-  }
   // Not possible ???
   if (v == -INFINITY){
     cell_printf(xpos, ypos, FONT_b"%s-INF", buf2);
@@ -1480,15 +1499,15 @@ static void trace_print_value_string(     // Only used at one place
   }
   const char *format;
   if (UNIT_IS_LINEAR(setting.unit))
-    format = FONT_s"%s %.3F%s%s"; // 5 characters incl u, m, etc...
+    format = FONT_s"%s %.3F%s%s%s"; // 5 characters incl u, m, etc...
   else
-    format = FONT_s"%s %.1f%s%s";
+    format = FONT_s"%s %.1f%s%s%s";
 #ifdef TINYSA4
   format++; // Skip small prefix for bold output
 #else
   if (bold) format++; // Skip small prefix for bold output
 #endif
-  cell_printf(xpos, ypos, format, buf2, v, unit_string[unit_index], (mtype & M_NOISE?"/Hz":(mtype & M_AVER?"/T":"")));
+  cell_printf(xpos, ypos, format, buf2, v, unit_string[unit_index], (mtype & M_NOISE?"/Hz":""), (mtype & M_AVER?"/T":""));
 }
 
 static void cell_draw_marker_info(int x0, int y0)
@@ -1608,21 +1627,14 @@ static void cell_draw_marker_info(int x0, int y0)
 #ifdef __NOISE_FIGURE__
     } else if (i>=2 && setting.measurement == M_NF && markers[0].enabled) {
       float aNP = 0;
-#if 1
-      for (int i =0; i < sweep_points; i++) {
-        aNP += actual_t[i];
-      }
-      aNP /= sweep_points;
-#else
       aNP = marker_to_value(0);
-#endif
+      float mNF = aNP + 173.93 - nf_gain;   // measured noise figure at 20C
-      float mNF = aNP -  logf(actual_rbw_x10*100.0) * (10.0/logf(10.0)) + 173.93 + SI4463_noise_correction_x10/10.0;   // measured noise figure at 20C
       if (nf_gain != 0) {
-        float mnf = expf((mNF - nf_gain)/10 * logf(10));     // measure noise factor
+        float mnf = expf(mNF/10.0 * logf(10));     // measure noise factor
-        float tnf = expf(config.noise_figure/10 * logf(10));     // tinySA noise factor
+        float tnf = expf(config.noise_figure/10.0 * logf(10.0));     // tinySA noise factor
-        float amp_gain = expf(nf_gain/10 * logf(10));
+        float amp_gain = expf(nf_gain/10.0 * logf(10.0));
         float anf = mnf - (tnf - 1.0)/amp_gain;
-        mNF = 10*logf(anf)/logf(10);
+        mNF = 10.0*logf(anf)/logf(10.0);
       }
       // powf(10,x) =  expf(x * logf(10))
       // log10f(x)  =  logf(x)/logf(10)

sa_core.c

@@ -3320,7 +3320,7 @@ again:                                                              // Spur redu
         }
         set_freq(ADF4351_LO, target_f);
 #if 1                                                               // Compensate frequency ADF4350 error with SI4468
-        if (actual_rbw_x10 < 3000 || setting.frequency_step < 100000) {
+        if (actual_rbw_x10 < 10000 || setting.frequency_step < 100000) {
         int32_t error_f = 0;
         if (real_old_freq[ADF4351_LO] > target_f) {
           error_f = real_old_freq[ADF4351_LO] - target_f;
@@ -3588,11 +3588,13 @@ again:                                                              // Spur redu
         my_step_delay = my_step_delay * 2;
 //      if (LO_shifted) // || SI4463_offset_changed)
 //        my_step_delay = my_step_delay * 2;
+#if 0   // Always have some delay before measuring RSSI
       if (old_R < 4 && actual_rbw_x10 >= 1000 && SI4463_frequency_changed && ADF4351_frequency_changed) {
         my_step_delay -= 200;                   // compensate for additional delay of setting SI4463
         if (my_step_delay < 0)
           my_step_delay = 0;
       }
+#endif
       my_microsecond_delay(my_step_delay * (old_R > 5  ? 8 : (old_R > 3  ? 2 : 1)));
       ADF4351_frequency_changed = false;
       SI4463_frequency_changed = false;
@@ -3738,7 +3740,7 @@ static bool sweep(bool break_on_operation)
   float vbw_rssi;
 #endif
 #endif
-
+  clear_marker_cache();
   again:                          // Waiting for a trigger jumps back to here
   setting.measure_sweep_time_us = 0;                   // start measure sweep time
   //  start_of_sweep_timestamp = chVTGetSystemTimeX();    // Will be set in perform

ui_sa.c

@@ -1347,7 +1347,7 @@ static UI_FUNCTION_ADV_CALLBACK(menu_measure_acb)
     case M_NF:                             // noise figure
 //      reset_settings(setting.mode);
       markers[0].enabled = M_ENABLED;
-      markers[0].mtype = M_NOISE;          // Not tracking
+      markers[0].mtype = M_NOISE | M_AVER;          // Not tracking
       set_extra_lna(true);
       kp_help_text = "Amplifier Gain ";
       float old_gain = setting.external_gain;