Users are responsible for supplying an external LO based upon their application needs and requirements.

Note NI recommends that users connect, configure, and start generating from the external LO prior to starting RTG or calibration.

Supply the LO In Frequency (Hz) and LO In Power (dBm) as configuration parameters for the RTG.

Note Configure the LO In Frequency and LO In Power when running the RTG UI or RTG example.

Configuring the LO In Frequency (Hz)

Users can configure the LO In Frequency to the RTG center frequency or to a different frequency within the upconverter/downconverter passband. The RTG software returns the expected LO In Frequency value based upon the VST instrument and center frequency. Refer to the specifications for the External LO hardware for information about the supported LO In Frequency range.

Note NI recommends setting the LO In Frequency to the RTG center frequency during calibration.

Configuring the LO In Power (dBm)

Users can configure the LO In Power. The RTG software returns an expected LO In power based upon the mid-point value of the input range for a specific VST model. Refer to the specifications for the External LO hardware for information about the supported LO Input power range.

Note Users are responsible for measuring the RF path loss between the external LO source and the RTG LO In port.
Note Providing inaccurate external LO parameters to the RTG software may result in sub-optimal performance.
Note To achieve the best performance, some experimentation may be required to optimize the RTG LO In power for both the actual power of the supplied LO as well as the parameter passed to the RTG software.

Configuring the External LO Synchronization

NI recommends sharing the external LO reference clock with the RTG system. Sharing the same reference clock ensures the external LO and RTG system are disciplined to the same timebase. Share the same reference clock across all RTG system instruments in one of the following ways:

  • External LO Reference Clock to PXI Express Chassis Timing and Synchronization—Reference clocks shared using this method are automatically imported or exported depending upon connectivity. Refer to the System Reference Clock section in the user manual for the PXIe chassis for more information.
  • External LO Reference Clock to PXI Express Timing and Synchronization Module—Users are responsible for controlling the Timing and Synchronization Module to either import or export the reference clock.