From b056dab06e0f90a9ad3e50ae8e2b1c2367565599 Mon Sep 17 00:00:00 2001
From: boblark <bob@janbob.com>
Date: Tue, 14 Feb 2023 09:57:58 -0800
Subject: [PATCH] Added IQ corrections for hardware errors

---
 radioCESSB_Z_transmit_F32.cpp | 11 +++++++++++
 radioCESSB_Z_transmit_F32.h   | 15 +++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/radioCESSB_Z_transmit_F32.cpp b/radioCESSB_Z_transmit_F32.cpp
index c5304e9..e90c6c7 100644
--- a/radioCESSB_Z_transmit_F32.cpp
+++ b/radioCESSB_Z_transmit_F32.cpp
@@ -228,6 +228,17 @@ void radioCESSB_Z_transmit_F32::update(void)  {
       countPower1++;
       }
 
+   // Optional corrections to compensate for external hardware errors
+   if(useIQCorrection)
+      {
+	  for(int k=0; k<nC; k++)
+	     {
+         workingDataI[k] *= gainI;
+         workingDataI[k] += crossIQ*workingDataQ[k];
+         workingDataQ[k] += crossQI*workingDataI[k];
+	     }
+      }
+
    // Finally interpolate to 48 or 96 ksps. Data is in workingDataI[k]
    // and is 64 samples for audio 48 ksps.
    for(int k=0; k<nC; k++)   // Audio sampling at 48 ksps:  0 to 63
diff --git a/radioCESSB_Z_transmit_F32.h b/radioCESSB_Z_transmit_F32.h
index 672dfd4..0fd3122 100644
--- a/radioCESSB_Z_transmit_F32.h
+++ b/radioCESSB_Z_transmit_F32.h
@@ -254,6 +254,16 @@ public:
         gainOut = gOut;
 	    }
 
+    // Small corrections at the output end of this object can patch up hardware flaws.
+    // _gI should be close to 1.0, _gXIQ and _gXQI should be close to 0.0.
+    void setIQCorrections(bool _useCor, float32_t _gI, float32_t _gXIQ, float32_t _gXQI)
+        {
+        useIQCorrection = _useCor;
+        gainI = _gI;
+        crossIQ = _gXIQ;
+        crossQI = _gXQI;
+	    }
+
     // The LSB/USB selection depends on the processing of the IQ signals
     // inside this class.  It may get flipped with later processing.
     void setSideband(bool _sbReverse)
@@ -279,6 +289,11 @@ private:
     uint16_t  block_length = 128;
     bool sidebandReverse = false;
 
+    bool useIQCorrection = false;
+    float32_t gainI = 1.0f;
+    float32_t crossIQ = 0.0f;
+    float32_t crossQI = 0.0f;
+
     float32_t pStateDecimate[128 + 65 - 1];    // Goes with CMSIS decimate function
     arm_fir_decimate_instance_f32 decimateInst;