Hi Rob, The signal is actually sweeping over 4MHz, but is just super zoomed into a small piece to show the time delta so it looks CW. The time difference appears to be the same (within my ability to measure) across the band so I am assuming it is a time delay offset.
Any suggestions on how to reduce this time delay offset? Thanks, Michael Toussaint On Mon, Jun 5, 2023 at 8:51 PM Rob Kossler <rkoss...@nd.edu> wrote: > Hi Michael, > Either a delay offset OR a phase offset will show itself as a relative > phase. In order to distinguish between a delay offset and a phase offset, > your signal must have appreciable bandwidth. It appears that your signal > is CW. It is entirely possible that your delay offset is zero. Does this > make sense? > Rob > > On Mon, Jun 5, 2023 at 5:32 PM Michael Toussaint <mtoussa...@chaosinc.com> > wrote: > >> Could you share how you're setting up LO sharing in your code, as well as >> how you're setting the system clock on the N321? >> >> The functions "configure_channels" and "set_lo_hw_exports" are used to >> set up the LO sharing. >> >> The functions "sync_sources" and "sync_all_devices" are used to set up >> the system clock on the N321. >> >> How do you measure the relative delay? >> >> We are measuring the offset of the LO's by just measuring the phase >> difference of the RF coming out of the Ettus with an Oscilloscope (picture >> attached as >> Scope_Trace_SingleStream_LO.png >> >> <https://mail.google.com/mail/u/0?ui=2&ik=34abf4583b&attid=0.1&permmsgid=msg-a:r-1207093291428225864&view=att&disp=safe&realattid=f_lijcykt50>). >> Yellow is Channel 1, Green is Channel 2; using a single streamer we still >> appear to have a 2.64ns delta or ~135 degree phase shift. >> >> Thanks Marcus and Rob for your assistance. >> >> Michael Toussaint >> >> def sync_sources(usrp): >> logging.info('Setting Sync Sources') >> >> usrp.set_sync_source(clock_source = 'gpsdo', >> time_source = 'gpsdo') >> >> def sync_all_devices(hw_info): >> logging.info('Syncing All Devices') >> >> mb_with_gps_locked = -1 >> >> while 1: >> time.sleep(1.0) >> >> all_ref_locked = True >> >> for board in range(hw_info.usrp.get_num_mboards()): >> all_ref_locked = all_ref_locked and \ >> hw_info.usrp.get_mboard_sensor('ref_locked', >> board).to_bool() >> >> if (mb_with_gps_locked == -1) and \ >> hw_info.usrp.get_mboard_sensor('gps_locked', >> board).to_bool(): >> mb_with_gps_locked = board >> >> if all_ref_locked: >> logging.info('All Devices are REF locked') >> break >> >> logging.info('GPS Locked on MB #%d', mb_with_gps_locked) >> >> time.sleep(1.0) >> hw_info.usrp.set_time_next_pps( >> uhd.types.TimeSpec( >> hw_info.usrp.get_mboard_sensor('gps_time', >> mb_with_gps_locked).to_int() + >> 1.0) >> ) >> time.sleep(1.0) >> >> >> def configure_channels(usrp, rf_type, hw_info): >> rf_channel_index = None >> set_rf_rate = None >> set_rf_freq = None >> set_rf_gain = None >> set_rf_lo_source = None >> get_rf_lo_source = None >> get_rf_lo_freq = None >> get_rf_lo_freq_range = None >> >> if (rf_type == 'rx'): >> if (len(hw_info.rx_channel_index) > 0): >> rf_channel_index = hw_info.rx_channel_index >> set_rf_rate = usrp.set_rx_rate >> set_rf_freq = usrp.set_rx_freq >> set_rf_gain = usrp.set_rx_gain >> set_rf_lo_source = usrp.set_rx_lo_source >> get_rf_lo_source = usrp.get_rx_lo_source >> get_rf_lo_freq = usrp.get_rx_lo_freq >> get_rf_lo_freq_range = usrp.get_rx_lo_freq_range >> else: >> return >> elif (rf_type == 'tx'): >> if (len(hw_info.tx_channel_index) > 0): >> rf_channel_index = hw_info.tx_channel_index >> set_rf_rate = usrp.set_tx_rate >> set_rf_freq = usrp.set_tx_freq >> set_rf_gain = usrp.set_tx_gain >> set_rf_lo_source = usrp.set_tx_lo_source >> get_rf_lo_source = usrp.get_tx_lo_source >> get_rf_lo_freq = usrp.get_tx_lo_freq >> get_rf_lo_freq_range = usrp.get_tx_lo_freq_range >> else: >> return >> >> logging.info('Configuring %s Channels', rf_type.upper()) >> >> for rf_ch_name, rf_ch_index in rf_channel_index.items(): >> logging.info('Configuring %s channel %s (channel #%d)', >> rf_type.upper(), rf_ch_name, rf_ch_index) >> >> ch_def = hw_info.channel_def[rf_ch_name] >> >> # LO Channel Setup >> current_lo_name = 'unknown' >> current_lo_src = 'unknown' >> >> if ch_def.lo_inputs is not None: >> logging.info(' Setting %s LO for Channel %s (#%d)', >> rf_type.upper(), rf_ch_name, rf_ch_index) >> >> set_rf_lo_source(ch_def.lo_inputs.source, >> ch_def.lo_inputs.name, >> rf_ch_index) >> current_lo_name = ch_def.lo_inputs.name >> >> logging.info(' (#%d) Requested %s LO name %s, src %s', >> rf_ch_index, >> rf_type.upper(), >> ch_def.lo_inputs.name, >> ch_def.lo_inputs.source) >> else: >> logging.info(' No %s LO inputs for Channel %s (#%d)', >> rf_type.upper(), rf_ch_name, rf_ch_index) >> >> current_lo_name = 'lo1' >> >> current_lo_src = get_rf_lo_source(current_lo_name, >> rf_ch_index) >> >> logging.info(' (#%d) Current %s LO name %s, src %s', >> rf_ch_index, >> rf_type.upper(), >> current_lo_name, >> current_lo_src) >> >> rf_lo_freq = get_rf_lo_freq(current_lo_name, >> rf_ch_index) >> >> logging.info(' (#%d) [%s] Current %s LO freq %d', >> rf_ch_index, >> current_lo_name, >> rf_type.upper(), >> rf_lo_freq) >> >> rf_lo_freq_range = get_rf_lo_freq_range( >> current_lo_name, rf_ch_index) >> >> temp = ' (#%d) [%s] Current %s LO freq range' + \ >> ' [%d, %d] step %d' >> >> logging.info(temp, >> rf_ch_index, >> current_lo_name, >> rf_type.upper(), >> rf_lo_freq_range.start(), >> rf_lo_freq_range.stop(), >> rf_lo_freq_range.step()) >> >> logging.info(' Setting Sampling Rate %s', hw_info.fs) >> set_rf_rate(hw_info.fs, rf_ch_index) >> >> logging.info(' Setting Center Freq %s', hw_info.fc) >> tr = set_rf_freq(uhd.libpyuhd.types.tune_request(hw_info.fc), >> rf_ch_index) >> >> logging.info(' (#%d) %s Tune Result:', >> rf_ch_index, rf_type.upper()) >> log_tune_result(tr) >> >> logging.info(' Setting %s Gain: %2.3f db', >> rf_type.upper(), >> ch_def.gain) >> set_rf_gain(ch_def.gain, rf_ch_index) >> >> def set_lo_hw_exports(usrp, node_name, dirx, lo_enabled, output_array): >> """Set LO HW Exports""" >> if (lo_enabled is None) or (output_array is None): >> return >> >> logging.info('Setting %s LO Export Enabled for %s', >> dirx.upper(), node_name) >> >> if dirx.lower() == 'rx': >> usrp.set_rx_lo_export_enabled(lo_enabled, 'lo1', 0) >> enable_val = usrp.get_rx_lo_export_enabled('lo1') >> elif dirx.lower() == 'tx': >> usrp.set_tx_lo_export_enabled(lo_enabled, 'lo1', 0) >> enable_val = usrp.get_tx_lo_export_enabled('lo1') >> else: >> logging.warning('Invalid direction %s', dirx) >> return >> >> logging.info(' %s LO Export Enabled = %s, requested %s', >> dirx.upper(), enable_val, lo_enabled) >> >> temp_path = 'blocks/0/Radio#0/dboard/' + \ >> f'{dirx.lower()}_frontends/' + \ >> '0/los/lo1/lo_distribution/LO_OUT_{}/export' >> >> logging.info('Setting %s LO HW Outputs for %s', >> dirx.upper(), node_name) >> >> for out_num in range(len(output_array)): >> hw_lo_export_path = temp_path.format(out_num) >> >> if usrp.get_tree().exists(hw_lo_export_path): >> usrp.get_tree().access_bool(hw_lo_export_path).set( >> output_array[out_num]) >> >> logging.info(' %s LO HW Export Out[%d] = %s, %s %s', >> dirx.upper(), out_num, >> usrp.get_tree().access_bool( >> hw_lo_export_path).get(), >> 'requested', >> output_array[out_num]) >> else: >> logging.warning(' %s LO HW Export Out[%d] does not exist', >> dirx.upper(), out_num) >> >> >> On Thu, May 25, 2023 at 6:45 AM Rob Kossler <rkoss...@nd.edu> wrote: >> >>> On Thu, May 25, 2023 at 3:54 AM Michael Toussaint >>> <mtoussa...@chaosinc.com> wrote: >>> > >>> > Used a single streamer and saw the delay slightly improve to between >>> 2.5 - 3 ns. >>> > >>> > Any other suggestions to improve the delay to match the results from >>> the knowledge base, https://kb.ettus.com/USRP_N320/N321_LO_Distribution? >>> >>> How do you measure the relative delay? >>> >> >> >>
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