Use c_wg_phase_offset to keep c_wg_sst_margin = 0.01 for wg_ampl = 0.001.

Closes L2SDP-1011

test/py/control/stat_stream_sst.py

@@ -287,7 +287,7 @@ class SstStatisticStream:
             record_time = 2.0 if recv_time < 2.0 else recv_time + 1.0
             self.stream_control.record_time(record_time)
             self.logger.info("Received %d BSN's", self.stream_reader.data.nof_received_bsn())
-            
+
             # now analyse the data
             success = True
             self.next_packet_nr = 0
@@ -324,7 +324,7 @@ class SstStatisticStream:
             except BaseException as err:
                 if handle_exception(err) == 1:
                     return
-                
+
             if n_valid_packets == 0:
                 success = False
 
@@ -363,9 +363,21 @@ class SstStatisticStream:
         # wg_ampl = 0.1     # SST SB-102 = 8300194881257
         # wg_ampl = 1.0     # SST SB-102 = 830172237735488
 
+        # Maximum difference in measured and expected SST value at subband wg_sub
+        c_wg_sst_margin = 0.01
+
+        # For smallest wg_ampl = 0.001 the exact SST level depends more on the WG phase, due
+        # to quantization noise. For wg_phase = 0.0 the c_wg_sst_margin = 0.01 is still
+        # suitable, provided that the WG phase is adjusted for the shiftram latency to
+        # effectively keep wg_phase = 0.0.
+        # If the c_wg_phase_offset = 0, then c_wg_sst_margin = 0.02 would be needed to verify
+        # the SST result when wg_ampl = 0.001.
+        c_sdp_shiftram_latency = 3.0
+        c_wg_phase_offset = 360.0 * c_sdp_shiftram_latency * (wg_sub / C_SDP.N_fft)
+
         success = True
         for wg_ampl in [1.0, 0.1, 0.01, 0.001]:
-            wg_phase = 0.0
+            wg_phase = 0.0 + c_wg_phase_offset
             wg_freq = wg_sub * C_SDP.f_sub  # WG sinus subband frequency in Hz
 
             # Determine expect SST level at WG frequency subband
@@ -380,7 +392,7 @@ class SstStatisticStream:
             wg.set_sinus(wg_ampl, wg_phase, wg_freq)
             wg.enable()
             time.sleep(7.0)
-            
+
             # first read in the data.
             if self.stream_control.record_n_bsn(n_bsn=3):
                 self.logger.info("Received %d BSN's:", self.stream_reader.data.nof_received_bsn())
@@ -391,7 +403,7 @@ class SstStatisticStream:
 
             # now analyse the data
             bsn = self.stream_reader.data.get_all_bsn()[1]
-                    
+
             self.logger.info(f"Test SST at BSN {bsn} for WG ampl {wg_ampl}")
             # get list of all s_ant signal input indices of rx packets in the integration interval
             all_index = list(self.stream_reader.data.get_all_index(bsn))
@@ -406,7 +418,7 @@ class SstStatisticStream:
                     # at WG subband index and near zero for all other subbands
                     sst_relative = sst_value / exp_sub_sst
                     if sub == wg_sub:
-                        if sst_relative < 0.99 or sst_relative > 1.01:
+                        if sst_relative < 1.0 - c_wg_sst_margin or sst_relative > 1.0 + c_wg_sst_margin:
                             self.logger.error(
                                 f"si-{si}, sub-{sub} SST value={sst_value} at WG freq differs too much from expected (sst_relative = {sst_relative})"
                             )
@@ -417,7 +429,7 @@ class SstStatisticStream:
                                 f"si-{si}, sub-{sub} SST value={sst_value} differs too much from zero (sst_relative = {sst_relative})"
                             )
                             success = False
-            
+
         wg.disable()
         self.stream_control.stream_off()
         print_result("test_data", success)