Using NI Vector Signal Analyzer as Downconverter

NI Vector Signal Analyzer (VSA) comprises of following devices:

• RF Analog Signal Generator (e.g. PXIe 5653)
• RF Signal Downconverter (e.g. PXIe 5606)
• IF Digitizer (e.g. PXIe 5624)

This article discusses how we can configure NI VSA as a downconverter-only instrument. The article uses LabVIEW  and the PXIe-5668 VSA for reference. The approach discussed here can be used for other programming environments and PXI Vector Signal Analyzer modules.
The article assumes familiarity with LabVIEW and NI VSA modules and is intended for audiences who want to use NI VSA as a downconverter with external digitizer modules or instruments. Kindly download and install the NI-RFSA driver.

Configure NI Measurement & Automation Explorer (NI MAX)

1. Open NI MAX.

2. Select VSA (e.g. 5668) >> In Associated Devices section Specify Digitizer as “External”.

3. Select the correct Local Oscillator module from the drop-down menu against LO.

4. Click the “Save” button at the top.

LabVIEW Example

1. In LabVIEW, go to Help >> Find Examples.
2. In NI Example Finder browse to folder Hardware Input and Output >> Modular Instruments >> NI-RFSA >> Utilities.
3. Open RFSA Downconverter with External Digitizer vi.

4. Configure the following Device Parameters; Resource Name, Center Frequency, and Reference Level in this example.

(Optional) Device-Specific Configuration

NI-RFSA drivers allow additional device-specific configuration apart from the one provided in example vi.
For example, PXIe-5668 can be configured for IF Output frequency of 190MHz, 199MHz, 187.5 MHz, 507.5 MHz, or 730 MHz. PXIe-5606 (downconverter in PXIe-5668) IF Output frequency can be configured by appropriately configuring the IF Filter BW property of NI-RFSA. PXIe-5606 Downconverter IF Filter can be set to 200 MHz/320 MHz, for IF of 730 MHz. As shown in the image below, the user can add a property node in the block diagram of the above example to specify IF Filter Bandwidth.

With the above steps, the user will be able to configure NI VSA as a downconverter. IF signal will be available at IF Output connector of PXI Downconverter module.