TwinRX: Spur cleanup

- Reduce FRAC2 and MOD2 values on ADF5356
- Add write to register 10 and delay during retune on ADF5356
- Make negative bleed conditional on integer or fractional N mode for
ADF5356
- Tune unused LOs out of band to remove interference

Signed-off-by: michael-west <michael.west@ettus.com>

1 files changed, 27 insertions, 6 deletions

diff --git a/host/lib/usrp/dboard/twinrx/twinrx_experts.cpp b/host/lib/usrp/dboard/twinrx/twinrx_experts.cpp
index d196d99e2..8d3ba591b 100644
--- a/host/lib/usrp/dboard/twinrx/twinrx_experts.cpp
+++ b/host/lib/usrp/dboard/twinrx/twinrx_experts.cpp
@@ -617,7 +617,10 @@ void twinrx_settings_expert::_resolve_lox_freq(lo_stage_t lo_stage,
     bool hopping_enabled)
 {
     if (ch0_lo_source == twinrx_ctrl::LO_EXTERNAL) {
-        // If the LO is external then we don't need to program any synthesizers
+        if (synth0_mapping != MAPPING_CH1) {
+            // Tune the internal LO away to avoid interference
+            _set_lox_synth_freq(lo_stage, twinrx_ctrl::CH1, ch0_freq_d + 100e6);
+        }
         ch0_freq_c = ch0_freq_d;
     } else {
         // When in hopping mode, only attempt to write the LO frequency if it is actually
@@ -631,15 +634,24 @@ void twinrx_settings_expert::_resolve_lox_freq(lo_stage_t lo_stage,
             ch0_freq_c = _set_lox_synth_freq(lo_stage, twinrx_ctrl::CH2, ch0_freq_d);
         } else if (synth0_mapping == MAPPING_SHARED or synth1_mapping == MAPPING_SHARED) {
             // If any synthesizer is being shared then we are not in hopping mode
+            // Tune the LO being shared
             twinrx_ctrl::channel_t ch =
                 (synth0_mapping == MAPPING_SHARED) ? twinrx_ctrl::CH1 : twinrx_ctrl::CH2;
             ch0_freq_c = _set_lox_synth_freq(lo_stage, ch, ch0_freq_d);
             ch1_freq_c = ch0_freq_c;
+
+            // Tune the synthesizer of the other channel away to avoid interference
+            twinrx_ctrl::channel_t other_ch =
+                (synth0_mapping == MAPPING_SHARED) ? twinrx_ctrl::CH2 : twinrx_ctrl::CH1;
+            _set_lox_synth_freq(lo_stage, other_ch, ch0_freq_d + 100e6);
         }
     }
 
     if (ch1_lo_source == twinrx_ctrl::LO_EXTERNAL) {
-        // If the LO is external then we don't need to program any synthesizers
+        if (synth1_mapping != MAPPING_CH0) {
+            // Tune the internal LO away to avoid interference
+            _set_lox_synth_freq(lo_stage, twinrx_ctrl::CH2, ch1_freq_d + 100e6);
+        }
         ch1_freq_c = ch1_freq_d;
     } else {
         // When in hopping mode, only attempt to write the LO frequency if it is actually
@@ -655,10 +667,19 @@ void twinrx_settings_expert::_resolve_lox_freq(lo_stage_t lo_stage,
             ch1_freq_c = _set_lox_synth_freq(lo_stage, twinrx_ctrl::CH2, ch1_freq_d);
         } else if (synth0_mapping == MAPPING_SHARED or synth1_mapping == MAPPING_SHARED) {
             // If any synthesizer is being shared then we are not in hopping mode
-            twinrx_ctrl::channel_t ch =
-                (synth0_mapping == MAPPING_SHARED) ? twinrx_ctrl::CH1 : twinrx_ctrl::CH2;
-            ch0_freq_c = _set_lox_synth_freq(lo_stage, ch, ch0_freq_d);
-            ch1_freq_c = ch0_freq_c;
+            // Tuning has already been done above if CH0 LO source is not external
+            if (ch0_lo_source == twinrx_ctrl::LO_EXTERNAL) {
+                // Tune the LO being shared
+                twinrx_ctrl::channel_t ch =
+                    (synth0_mapping == MAPPING_SHARED) ? twinrx_ctrl::CH1 : twinrx_ctrl::CH2;
+                ch0_freq_c = _set_lox_synth_freq(lo_stage, ch, ch0_freq_d);
+                ch1_freq_c = ch0_freq_c;
+
+                // Tune the synthesizer of the other channel away to avoid interference
+                twinrx_ctrl::channel_t other_ch =
+                    (synth0_mapping == MAPPING_SHARED) ? twinrx_ctrl::CH2 : twinrx_ctrl::CH1;
+                _set_lox_synth_freq(lo_stage, other_ch, ch0_freq_d + 100e6);
+            }
         }
     }
 }