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RFmx Overview

    Last Modified: February 6, 2018

    NI-RFmx is a family of instrument drivers that share a single session handle across multiple drivers. You need to open only one RFmx session per signal analyzer, and you use that single session handle to configure and perform measurements with the different RFmx drivers, such as SpecAn, Demod, LTE, and so on.

    The RFmx driver APIs have a shared set of API nodes for opening and closing the RFmx session as well as configuring hardware settings, such as the Reference Clock configuration, that are shared across drivers. These shared nodes are called the RFmxInstr driver. RFmxInstr does not contain any measurements, and you always use RFmxInstr along with one or more other RFmx drivers that expose the measurements you need to perform.

    Because you must use RFmxInstr nodes to use the RFmx drivers that contain the measurements, for convenience, commonly used nodes, such as RFmxInstr Initialize NIRFSA node, RFmxInstr Close node, and RFmxInstr Wait for Acquisition Complete node, are replicated in the LabVIEW palettes for the other RFmx drivers.

    The following is an example of how you use the RFmx API drivers in LabVIEW to capture a spectrum using the RFmx SpecAn driver. The same sequence applies to other ADEs as well.

    1. Open an RFmx session using NI-RFmxInstr.
    2. Configure the frequency reference using the nodes or the properties in NI-RFmxInstr.
    3. Configure the reference level, frequency, and span using NI-RFmxSpecAn.
    4. Select the Spectrum measurement using RFmxSpecAn Select Measurement node.
    5. Initiate the measurement using NI-RFmxSpecAn.
    6. Fetch the spectrum using NI-RFmxSpecAn.
    7. Close the RFmx session using NI-RFmxInstr or NI-RFmxSpecAn.

    When you use RFmxInstr nodes to configure hardware settings in an RFmx session, those settings apply to all the RFmx drivers that are present in the same RFmx session. However, the following settings are RFmx driver-specific and are not shared across different RFmx drivers within the same RFmx session:

    • Center frequency
    • Reference level
    • External attenuation
    • Trigger settings

    For example, if you are making both RFmx LTE and RFmx WCDMA measurements within one RFmx session, setting the frequency in RFmx LTE does not affect the frequency used in RFmx WCDMA.

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