The timebases of the PXIe-5831 modules must be frequency-locked to a common reference clock. The following clock sources are available:

  • 10 MHz Onboard Reference Clock of the PXIe-3622 Vector Signal Up/Down Converter—The PXIe-3622 onboard reference clock source supplies the reference clock.
  • 10 MHz External Reference Clock—Connect the external clock signal, from your stable frequency reference, to the REF IN connector on the PXIe-3622.
  • 10 MHz PXI Express Backplane Clock—This 10 MHz Reference Clock signal is supplied on the PXI backplane.

    • Configuring Onboard Reference Clock Timing

    You can use the 10 MHz onboard Reference Clock of either the PXIe-5653 LO Source or PXIe-3622 Vector Signal Up/Down Converter, depending on the hardware configuration you purchased.

    PXIe-5831 IF and mmWave Instrument

    The default configuration of the PXIe-5831 with an associated PXIe-5653 is to export a 10 MHz signal from the PXIe-5653 to the PXIe-3622 and the PXIe-3622 to export a 10 MHz signal to the PXIe-5820.

    Complete the following steps to apply this configuration.

    1. Use the 87 mm MMCX (m)-to-MMCX (m) cable to connect the PXIe-5820 REF IN front panel connector to the PXIe-3622 REF OUT front panel connector.
    2. Use one of the 152 mm MMPX (m)-to-SMA (m) cables to connect the PXIe-3622 REF IN front panel connector to the PXIe-5653 REF OUT (10 MHz) front panel connector.
    3. Using NI-RFSA or NI-RFSG, set the Ref Clock Source property or attribute to OnboardClock.

    PXIe-5831 IF Only Instrument

    The default configuration of the PXIe-5831 is to export a 10 MHz signal from the PXIe-3622 to PXIe-5820.

    Complete the following steps to apply this configuration.

    1. Use the 87 mm MMCX (m)-to-MMCX (m) cable to connect the PXIe-5820 REF IN front panel connector to the PXIe-3622 REF OUT front panel connector.
      This completes the Reference Clock connection.
    2. Using NI-RFSA or NI-RFSG, set the Ref Clock Source property or attribute to OnboardClock.

    Configuring External Reference Clock Timing

    Complete the following steps to configure the PXIe-5831 to lock to an external reference source.

    1. Connect the external signal to the appropriate module, depending on your hardware configuration.
      ConfigurationConnection Description
      PXIe-5831 IF only instrument Connect the external signal to the PXIe-3622 REF IN connector.
      PXIe-5831 IF and mmWave instrument Connect the external signal to the PXIe-5653 REF IN connector.

      The clocks need to remain connected in their respective default configuration, as described in the preceding section.

    2. Set the NI-RFSA or NI-RFSGRef Clock Source property or attribute to RefIn as the Reference Clock source.

    Configuring PXI 10 MHz Backplane Clock Timing

    To configure the PXIe-5831 to use the PXI 10 MHz backplane clock, set the NI-RFSA or NI-RFSGRef Clock Source property or attribute to PXI_Clk.

    When using the PXIe-5831 IF and mmWave instrument configuration, the PXIe-5653 can lock to the PXI Express backplane Reference Clocks if the backplane Reference Clocks meet the frequency accuracy requirements of the PXIe-5653.

    Note The PXI Express backplane Reference Clock, when left free running, may not meet the accuracy requirements of the PXIe-5653. The PXIe-5653 requirements are more stringent than PXI Express backplane accuracy requirements because of the high-performance OCXO on the PXIe-5653. Locking to the PXI Express backplane Reference Clock requires that the PXI Express backplane Reference Clock be locked to another, more accurate external reference.

    Configuring PXIe-5653 Master Clock Timing

    This configuration is valid only when using the PXIe-5831 IF and mmWave instrument configuration, which includes the PXIe-5653 LO source module.

    To configure the PXIe-5831 to use the PXIe-5653 as the master clock, complete the following steps.

    1. Connect the PXIe-5653REF OUT (10 MHz) connector to the PXI chassis REF IN connector.
    2. Set the NI-RFSA or NI-RFSGRef Clock Source property or attribute to PXI_ClkMaster.

      NI-RFSA or NI-RFSG configures the PXIe-5653 to export the Reference Clock and configures the PXIe-5820 and PXIe-3622 to use PXI_Clk as the Reference Clock source.

      For best performance, configure all other modules in the instrument to use PXI_Clk as the Reference Clock source.