NI PXIe-5641R RIO IF Transceiver Example: Using the IF Transceiver with an NI PXI-5600 Downconverter

The NI PXIe-5641R takes the flexibility and strength of an IF transceiver and open-ended FPGA backend to the PXI Express form factor, allowing it to more easily interact with other PXI instruments. One of the common applications is capturing an RF waveform and performing some sort of processing on the data, whether it is through a field-programmable gate array (FPGA) or on the host. The following example illustrates how to program and control an NI PXI-5600 RF downconverter in unison with the NI PXIe-5641R IF transceiver using the NI-RFSA and NI-5640R drivers

Background:

The new NI PXIe-5641R RIO IF transceiver is an input/output device with a Virtex-5 FPGA core for reconfigurable processing. There are two 14-bit analog-to-digital (ADC) channels capable of 100 MS/s rates and bandwidth up to 20 MHz. Similarly there are two 14-bit digital-to-analog (DAC) channels capable of 200 MS/s rates. You can configure the DACs in interpolation or digital upconversion (DUC) modes, allowing for both narrowband IF downconversion and traditional AC-coupled signal generation.

With the PXI Express form factor, you can take advantage of the above capabilities with other PXI- or PXI Express-based instruments. Ranging from frequency translation to signal conditioning such as attenuation or filtering, these additional instruments can transform the NI PXIe-5641R from a stand-alone transceiver to an expanded and reconfigurable test system. This specific example illustrates how you can use the analog input channels of the NI PXIe-5641R with an NI PXI-5600 2.7 GHz RF downconverter.

High-frequency signals from 9 kHz to 2.7 GHz can be translated to an IF frequency of 15 MHz. This is accomplished via the PXI-5600 superheterodyne architecture.

 

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The PXI-5600 maintains a real-time bandwidth of 20 MHz. All frequency content at the RF frequency, ±10 MHz is completely transferred to the IF frequency. Attenuation at the RF front end and IF back end of the PXI-5600 is used to ensure that maximum dynamic range and linearity is preserved. The PXI-5600 is programmed using the NI-RFSA API.

 

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The 15 MHz IF signal is then digitally downconverted using one of the two ADC channels on the NI PXIe-5641R producing IQ complex baseband data. This IQ data represents a finite bandwidth of frequency from which analysis can be performed in both the time and frequency domains.

 

To ensure that frequency accuracy is maintained, the NI PXI-5600 and NI PXIe-5641R share a common reference clock which is sourced by the internal oscillator of the NI PXI-5600. This provides a shared frequency accuracy of 50 ppb. The reference clock is shared by connecting the 10 MHz Out SMA connector on the front panel of the NI PXI-5600 to the SMB connector on the front panel of the NI PXIe-5641R via a SMA to SMB flexible cable. The reference clock signal is exported by default by the RF downconverter, however you must configure the NI PXIe-5641R to received and lock to the signal.

 

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Example

The following example illustrates how to pair the NI PXIe-5641R with the NI PXI-5600 RF downconverter using the NI-5640R and NI-RFSA LabVIEW APIs.

1.      Open the ni5640R with PXI-5600 Downconverter LabVIEW Project.

2.      Open the ni5640R with PXI-5600 Downconverter (Host) VI

3.      The front panel, shown in Figure 5, have the following settings:

•         PXIe-5641R – The resource name of the NI PXIe-5641R in your system. This is a RIO target resource name.

•         PXI-5600 – The resource name of the PXI-5600 in your system.

•         Reference Level – The reference level of your RF system. Set this level based upon the peak power of the signal being acquired to maximize dynamic range and reduce distortion.

•         AI. Ch0 I Gain – Apply gain to the I data being acquired via the FPGA

•         AI.Ch0 Q Gain – Apply gain to the Q data being acquired via the FPGA

•         Center Frequency – Specify the RF center frequency you wish to tune to. This should be within 9 kHz to 2.7 GHz.

•         Span – Specify the bandwidth you wish to acquire. Valid inputs include 97.65 kHz to 25 MHz. This value may be coerced based upon available decimation rates.

•         Resolution Bandwidth- Specify the RBW of your acquisition. RBW will drive the bin size of the FFT applied, as well as the acquisition or record length.

4.      Set the above properties according to your specification.

5.      Click the run arrow. Verify that the acquisition is accurate and illustrative of the signal being measured.

This EPD contains example code written in both the NI-5640R traditional LabVIEW FPGA API and the newly released Asynchronous Wires Palette.

Requirements

Filename: 5641rwith5600examples.zip

Software Requirements

Application Software: LabVIEW Professional Development System
Toolkits and Add-Ons: Spectral Measurements Toolkit, LabVIEW FPGA Module
Language(s): LabVIEW

Hardware Requirements

Hardware Group: RF
Hardware Model: PXIe-5641R, PXI-5600
Driver: NI-RFSA, NI-5640R

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