Synchronization Using NI-RFSA and NI-RFSG

The PXIe-5645 allows for multidevice synchronization with Sample Clock-level alignment.

To perform multidevice synchronization, you must lock all devices to phase-aligned Reference Clocks. One way to do this is to specify PXI_CLK10 as the Reference Clock source for all devices. If you want to supply an external Reference Clock, some chassis allow you to override the PXI_CLK10 using an external reference input terminal on the chassis.

Alternatively, you can split the external Reference Clock with a passive power-divider or active distribution amplifier and provide a phase-aligned version to each PXIe-5645REF IN front panel connector. Refer to the PXIe-5645 Specifications document for details about the minimum and maximum levels allowed by the PXIe-5645REF IN front panel connector.

Note The PXIe-5645 does not support multidevice synchronization with daisy-chained Reference Clocks, for example, REF OUT to REF IN.
Note This topic applies only when programming the PXIe-5645 using NI-RFSA and NI-RFSG.

NI-RFSA and NI-RFSG Synchronization Properties and Attributes

The PXIe-5645 supports synchronization using low-level properties and attributes instead of supporting NI-TClk synchronization. Use the NI-RFSA and NI-RFSG properties and attributes in the following tables to synchronize the PXIe-5645 with another PXIe-5645 or to synchronize the generator and analyzer on one PXIe-5645 device.

NI-RFSA Property NI-RFSA Attribute
Sync Start Trigger Master NIRFSA_ATTR_SYNC_START_TRIGGER_MASTER
Sync Start Trigger Dist Line NIRFSA_ATTR_SYNC_START_TRIGGER_DIST_LINE
Sync Ref Trigger Master NIRFSA_ATTR_SYNC_REF_TRIGGER_MASTER
Sync Ref Trigger Dist Line NIRFSA_ATTR_SYNC_REF_TRIGGER_DIST_LINE
Sync Ref Trigger Delay Enabled NIRFSA_ATTR_SYNC_REF_TRIGGER_DELAY_ENABLED
Sync Advance Trigger Master NIRFSA_ATTR_SYNC_ADVANCE_TRIGGER_MASTER
Sync Advance Trigger Dist Line NIRFSA_ATTR_SYNC_ADVANCE_TRIGGER_DIST_LINE
NI-RFSG Property NI-RFSG Attribute
Sync Script Trigger Master NIRFSG_ATTR_SYNC_SCRIPT_TRIGGER_MASTER
Sync Script Trigger Dist Line NIRFSG_ATTR_SYNC_SCRIPT_TRIGGER_DIST_LINE
Sync Start Trigger Master NIRFSG_ATTR_SYNC_START_TRIGGER_MASTER
Sync Start Trigger Dist Line NIRFSG_ATTR_SYNC_START_TRIGGER_DIST_LINE

Sharing the LO Between Channels

For repeatable phase offsets between multiple RF channels, share the LO between channels.

The channels you share could be RF IN or RF OUT channels on multiple devices or on a single device. For example, to synchronize two analyzers in NI-RFSA or two generators in NI-RFSG, complete the following steps:

NI-RFSA

  1. Set the LO Export Enabled property or NIRFSA_ATTR_LO_EXPORT_ENABLED attribute to TRUE for one analyzer.
  2. Set the LO Source property or NIRFSA_ATTR_LO_SOURCE attribute to LO_In on the other analyzer.
  3. Set the LO Frequency property or NIRFSA_ATTR_LO_FREQUENCY attribute to the frequency of the LO signal you are providing to the device.
    If your I/Q carrier frequency is below 375 MHz, you must provide an LO signal to the LO IN terminal that is twice your I/Q carrier frequency and write this value to the LO Frequency property or the NIRFSA_ATTR_LO_FREQUENCY attribute.

NI-RFSG

  1. Set the LO Out Enabled property or NIRFSG_ATTR_LO_OUT_ENABLED attribute to TRUE for one generator.
  2. Set the LO Source property or NIRFSG_ATTR_LO_SOURCE attribute to LO_In on the other generator.
  3. Set the Upconverter Center Frequency (Hz) property or NIRFSG_ATTR_UPCONVERTER_CENTER_FREQUENCY attribute to the frequency of the LO signal you are providing to the device.