Electronic Design

PXI Modules Provide Higher Frequencies, Speed, And Flexibility

At last month’s NIWeek conference in Austin, Texas, National Instruments introduced several RF products that are sure to be a hit with some engineers because of their higher frequency range, faster speeds, and lower costs. With RF testing becoming a larger part of the design and production testing of wireless technologies, these devices could yield faster time-to-market while decreasing test costs. NI also rolled out a line of Wi-FI testers that promise remote data acquisition.

The PXIe-5663 vector signal analyzer (VSA) performs signal analysis from 10 MHz up to 6.6 GHz with up to 50 MHz of instantaneous bandwidth. It offers pass-band flatness and low phase noise so it can accurately measure modulated signals. Typical error vector magnitude (EVM) performance with WCDMA is 0.8% at 2 GHz for more than 2600 symbols. That compares favorably with measurements from regular bench instruments that cost many times more. Typical EVM performance for WiMAX is –52 dB and 3.8 GHz.

As for the PXIe-5673 vector signal generator (VSG), it can deliver signals from 85 MHz up to 6.6 GHz. It also uses direct RF upconversion to provide up to 100 MHz of instantaneous bandwidth. Engineers can take advantage of its “impairments mode,” using an internal FPGA to manually adjust the gain imbalance, IQ offsets, and quadrature skew. Carrier and image suppression can be better than –85 dBc at a specific frequency. Both the VSA and VSG use 16-bit analog-to-digital converters (ADCs) or digital-to-analog converters (DACs) respectively to achieve superior dynamic range performance.

The PXIe-1075 chassis offers 18 open slots for the VSA and VSG and other PXI modules using the PCI Express (PCIe) bus (Fig. 1). With its hybrid chassis, designers can use any of their PXIe modules. All slots have up to 1-Gbyte/s per slot bandwidth and up to 4-Gbyte/s total system bandwidth. The chassis operates from 0°C to 50°C and provides integrated system monitoring features such as power management, fan health, and temperature monitoring.

NI’s new RF test system works with its well-known LabVIEW software, which provides great measurement flexibility. Designers can develop their own wireless protocols or use standard specific LabVIEW toolkits, including WiMAX, GPS, WCDMA, GSM, EDGE, broadcast video, 802.11, Bluetooth, orthogonal frequency- division multiplexing (OFDM), and multiple-input multiple-output (MIMO). Users also can add multiple VSAs and VSGs as needed to provide the specific configuration for MIMO testing.

The latest version, LabVIEW 8.6, implements parallel measurement algorithms on multicore CPUs. This can mean significantly faster measurements than those made on more traditional instruments. With the new NI RF system, WCDMA measurements can be made 20 times faster than with traditional instruments. Also, a 50-MHz spectrum sweep with a 30-kHz resolution bandwidth takes only 4 ms when using the NI PXIe-8106 controller. Contrast that with the 100 ms for the same test using a traditional bench instrument. LabVIEW 8.6 supports future faster parallel processing as larger CPUs with four and more cores become available as well.

Meanwhile, NI’s Wi-Fi DAQ series of wireless Ethernet local-area network (LAN) products promises remote data acquisition (Fig. 2). When used with LabVIEW, they provide a convenient way to capture sensor data for structural diagnostics, environmental, or machine condition monitoring without the cost and inflexibility of cabling.

The Wi-Fi DAQ devices use the IEEE 802.11b/g standard to stream data from four ports at rates up to 100 ksamples/s with 24 bits of resolution. Their builtin advanced network authentication methods and 128-bit AES encryption provide the highest commercially available network security.

Also, the Wi-Fi DAQs include built-in signal conditioning and direct sensor connectivity with either BNC or screw terminal connections. Five different models are available with different data rates and signal conditioning. In addition to the five wireless devices, NI offers five similar models for direct Ethernet cable connectivity.

The PXIe-5663 VSA costs $22,999. The PXIe-5673 VSG costs $23,999. The PXIe-1075 costs $5999. Prices for the Wi-Fi DAQs start at $699. Contact the company for further information about availability.


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