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>

3 files changed, 49 insertions, 11 deletions

diff --git a/host/lib/include/uhdlib/usrp/common/adf535x.hpp b/host/lib/include/uhdlib/usrp/common/adf535x.hpp
index 736018da1..61dd88451 100644
--- a/host/lib/include/uhdlib/usrp/common/adf535x.hpp
+++ b/host/lib/include/uhdlib/usrp/common/adf535x.hpp
@@ -112,6 +112,7 @@ public:
         , _wait_fn(std::move(wait_fn))
         , _regs()
         , _rewrite_regs(true)
+        , _neg_bleed_changed(false)
         , _wait_time_us(0)
         , _ref_freq(0.0)
         , _pfd_freq(0.0)
@@ -350,6 +351,7 @@ private: // Members
     wait_fn_t _wait_fn;
     adf535x_regs_t _regs;
     bool _rewrite_regs;
+    bool _neg_bleed_changed;
     uint32_t _wait_time_us;
     double _ref_freq;
     double _pfd_freq;
@@ -602,6 +604,14 @@ inline double adf535x_impl<adf5356_regs_t>::_set_frequency(
     _regs.mod2_msb     = narrow_cast<uint16_t>(MOD2 >> 14);
     _regs.phase_24_bit = 0;
 
+    auto negative_bleed =   FRAC1 != 0 or FRAC2 != 0 ?
+                            adf5356_regs_t::NEGATIVE_BLEED_ENABLED :
+                            adf5356_regs_t::NEGATIVE_BLEED_DISABLED;
+    if (negative_bleed != _regs.negative_bleed) {
+        _regs.negative_bleed = negative_bleed;
+        _neg_bleed_changed = true;
+    }
+
     if (flush)
         commit();
     return coerced_out_freq;
@@ -630,9 +640,14 @@ inline void adf535x_impl<adf5356_regs_t>::_commit()
     } else {
         // Frequency update sequence from data sheet
         _write_fn(addr_vtr_t(ONE_REG, _regs.get_reg(13)));
-        _write_fn(addr_vtr_t(ONE_REG, _regs.get_reg(6)));
+        _write_fn(addr_vtr_t(ONE_REG, _regs.get_reg(10)));
+        if (_neg_bleed_changed) {
+            _write_fn(addr_vtr_t(ONE_REG, _regs.get_reg(6)));
+        }
         _write_fn(addr_vtr_t(ONE_REG, _regs.get_reg(2)));
         _write_fn(addr_vtr_t(ONE_REG, _regs.get_reg(1)));
+        _wait_fn(_wait_time_us);
         _write_fn(addr_vtr_t(ONE_REG, _regs.get_reg(0)));
     }
+    _neg_bleed_changed = false;
 }
diff --git a/host/lib/usrp/dboard/twinrx/twinrx_ctrl.cpp b/host/lib/usrp/dboard/twinrx/twinrx_ctrl.cpp
index 3686f4348..315861cd9 100644
--- a/host/lib/usrp/dboard/twinrx/twinrx_ctrl.cpp
+++ b/host/lib/usrp/dboard/twinrx/twinrx_ctrl.cpp
@@ -121,7 +121,7 @@ public:
                     [this](uint32_t microseconds) {
                         _db_iface->sleep(boost::chrono::microseconds(microseconds));
                     });
-                _lo1_iface[i]->set_pfd_freq(TWINRX_REV_C_PFD_FREQ);
+                _lo1_pfd_freq = TWINRX_REV_C_PFD_FREQ;
             } else {
                 _lo1_iface[i] = adf535x_iface::make_adf5355(
                     [this](const std::vector<uint32_t>& regs) {
@@ -130,13 +130,14 @@ public:
                     [this](uint32_t microseconds) {
                         _db_iface->sleep(boost::chrono::microseconds(microseconds));
                     });
-                _lo1_iface[i]->set_pfd_freq(TWINRX_REV_AB_PFD_FREQ);
+                _lo1_pfd_freq = TWINRX_REV_AB_PFD_FREQ;
             }
+            _lo1_iface[i]->set_pfd_freq(_lo1_pfd_freq);
             _lo1_iface[i]->set_output_power(adf535x_iface::OUTPUT_POWER_5DBM);
             _lo1_iface[i]->set_reference_freq(
                 _db_iface->get_clock_rate(dboard_iface::UNIT_TX));
             _lo1_iface[i]->set_muxout_mode(adf535x_iface::MUXOUT_DLD);
-            _lo1_iface[i]->set_frequency(3e9, 1.0e3);
+            _lo1_iface[i]->set_frequency(3e9, _lo1_pfd_freq / 2);
 
             // LO2
             _lo2_iface[i] =
@@ -561,7 +562,7 @@ public:
     double set_lo1_synth_freq(channel_t ch, double freq, bool commit = true)
     {
         boost::lock_guard<boost::mutex> lock(_mutex);
-        static const double RESOLUTION = 1e3;
+        static const double RESOLUTION = _lo1_pfd_freq / 2;
 
         double coerced_freq = 0.0;
         if (ch == CH1 or ch == BOTH) {
@@ -852,6 +853,7 @@ private: // Members
     twinrx_gpio::sptr _gpio_iface;
     twinrx_cpld_regmap::sptr _cpld_regs;
     spi_config_t _spi_config;
+    double _lo1_pfd_freq;
     adf535x_iface::sptr _lo1_iface[NUM_CHANS];
     adf435x_iface::sptr _lo2_iface[NUM_CHANS];
     lo_source_t _lo1_src[NUM_CHANS];
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);
+            }
         }
     }
 }