Several recent product introductions indicate that PXI is pushing ahead in the RF test arena. The frequency, bandwidth, and operating speed of PXI RF modules are all improving rapidly, while the size and power demands of modules are dropping. In addition, RF test is beginning to exploit the potential for portability inherent in PXI, allowing engineers to capture field data for playback in the laboratory.

At least two major vendors—Aeroflex and National Instruments—introduced RF test products for the PXI architecture at this year’s Autotestcon show (September 17–20, Baltimore, MD). Aeroflex announced a configurable RF test platform that included new hardware modules and instrumentation software as well as a chassis to tie them all together. The company also introduced SMART^E, a synthetic test environment for RF testing that supports PXI as well as LXI, cPCI, and GPIB instruments. National Instruments introduced an RF vector signal generator for PXI Express that can stream data from hard disk or PC memory to the generator at the instrument’s full data rate.

Both companies’ introductions demonstrate the ever-increasing performance that PXI instrumentation is achieving in RF applications. Tim Carey, Aeroflex product manager, explained that the Aeroflex 3030C 3-GHz and 3035C 6-GHz RF digitizers have extended their frequency range down from 330 kHz in previous generations to 250 kHz. At the same time, the new models offer a signal bandwidth to 90 MHz, up from 33 MHz. The new Aeroflex 3025C RF signal generator also offers a bandwidth extended to 90 MHz and has stretched its power output to a range from –120 dBm to +7 dBm.

The National Instruments PXIe-5672 RF vector signal generator brings to the table the ability to stream hours of data at 25 Msamples/s through its PXI Express interface. The ability to accept streaming data allows the generator to work from external data storage, which frees users from the limitations of onboard memory. The unit can generate signals from 250 kHz to 2.7 GHz with a 20-MHz instantaneous bandwidth.

Along with the performance improvements, the new generation of PXI RF products brings with it a reduced form factor. According to National Instruments’ senior product manager Joseph Kovacs, this reduction is a byproduct of technology improvements in the cellular and wireless markets.

“As that industry continues to grow and push its limits,” said Kovacs, “RF components get smaller, and we are able to use them to shrink the number of slots our products need. Our 5660 downconverter, for instance, occupied three slots when it was introduced. Two years later, technology had progressed and we got it down to two. We also gain real estate, which lets us fit more into the chassis.”

Kovacs also noted that these same technology trends are resulting in lower-power RF products. “Power is not an issue for a benchtop instrument, but for PXI, with its 25-W per slot power limits, it can be,” said Kovacs. “The cellular industry’s push for low power is thus benefiting PXI.”

Such reductions in power and size make it easier for system developers to create complete RF test and data-recording instruments small enough to be portable. As Kovacs explained, portable instruments allow test engineers to go out into the field and capture the real RF environment and then bring it back to the lab for use as a test stimulus instead of having to simulate complex scenarios such as multi-satellite GPS signals.

One of Aeroflex’s introductions directly targets such portable operation. The Model 3000A chassis is a ruggedized aluminum enclosure with built-in system controller, seven peripheral card slots, a 350-W power supply, and an 8.4-in. touch-screen color display. The presence of the touch-screen display and system controller, noted Carey, transforms the chassis into a self-contained, stand-alone instrument for either bench or portable operation. The chassis and components offer an extended operating temperature range of 0°C to 55°C, making the system applicable to field use, as well.

Portability is not the only benefit of shrinking RF components. Compact PXI RF components are also of interest in the military and aerospace markets, where size and weight are important considerations. The constraints of unmanned aircraft used in reconnaissance, NI’s Kovacs noted, make the small size of PXI an important benefit.

Small size and reduced power also benefit a major emerging market for PXI: manufacturing test. “We’re seeing that size is a big concern in manufacturing,” said Kovacs. “Space is a big deal. They [manufacturers] want a small footprint.” Kovacs pointed out that, for manufacturing, the ability to fit more test capability into a smaller area translates into more revenue per square foot.

The use of PXI in manufacturing test is an important market for both companies. Each promotes PXI as offering seamless migration from R&D to manufacturing, noting that the exact same instrument module that the designers use to develop a product can be incorporated into manufacturing test. This equipment commonality helps eliminate the need for test setups and procedures created at the bench to be re-created for testers on the production floor.

While both companies acknowledge this market duality, they are taking slightly different approaches to addressing it. Aeroflex has incorporated a number of features and options in its latest product offerings that target the key needs of manufacturing test: easy configuration and rapid test throughput. One way the company speeds test configuration is through complete, preconfigured systems that eliminate integration and compatibility concerns.

Aeroflex also offers software to speed testing. For its PXI Studio application software, the company has introduced plug-ins designed for the analysis of WiMAX signals, simplifying the setup and execution of compliance tests. The increased power range for the 3025C comes along with a 10X improvement in its ability to switch frequencies, with both features supporting the rapid test of RF components. Carey also noted that the increased bandwidth of the latest modules allows them to support virtually any wireless market, including cellular, wireless data, and RFIC test.

National Instruments prefers to keep its instrumentation more general in scope, according to Kovacs, and the company concentrates on the higher accuracy needs of the laboratory rather than the test speed needs of manufacturing. Kovacs also noted that NI keeps its products more general because it provides only the building blocks.

“Our partners are the ones that create systems,” said Kovacs. “Some are working with GSM and GPRS while others are working with RFID. Our approach is to produce products that will provide solutions all across the spectrum and avoid being pigeonholed in a single market segment.”

Whether aimed more at manufacturing or at the laboratory, the new generation of RF products shows that PXI is continuing to push the envelope for RF test. Shrinking footprints and power demands of modules are extending PXI’s applicability in both production floor and field environments; higher bandwidths are extending the range of signals that can be generated or analyzed; and faster bus transfers are making greater memory depths possible for generating more thorough and realistic testing. And the trends indicate that such gains will continue at least over the next few years.