PXI keeps pushing envelope
In some areas, the data-processing power available on PXI is even surpassing bench instrumentation.
By Richard A. Quinnell, Contributing Editor -- Test & Measurement World, 3/1/2010 12:00:00 AM
From its humble beginnings as a low-cost alternative to bench instrumentation, the PXI architecture has evolved to hold its own against high-end dedicated test systems. Now, advances in semiconductor integration and a weakened economy are helping PXI vendors to further push the envelope of what can be achieved with PXI. Modules for data acquisition, RF, switching, and data storage are among many that have continued improving, with vendors already planning for the next challenge.
|
A quick look at the PXI instrumentation released during the latter half of 2009 shows the levels to which PXI has risen. Adlink Technology, for instance, introduced its PCI-984x family of four-channel digitizers capable of sampling to 40 MHz at a resolution of 16-bits. ZTec Instruments released the ZT4440 series of digital sampling oscilloscopes capable of capturing 400 Msamples/s at 14-bit resolution. National Instruments created a suite of instrument modules that included the NI 4132 source-measurement unit, which offers sensitivity down to 10 pA. All compare favorably to available benchtop offerings. “Best-in-class instrumentation is now becoming available on PXI,” said Matt Friedman, NI’s senior product manager for the PXI platform.
The data-processing power available on PXI is even surpassing bench instrumentation in some areas. The advent of PXIe (PXI Express), for instance, virtually eliminated the backplane’s data-bandwidth limitation. “In terms of data transfers, PXI is now orders of magnitude faster than rack-and-stack instruments, approaching gigabyte transfer speeds between instruments and the host or storage,” said Friedman. To cite one example, Conduant recently released the PXIe-compatible NTX16 system that can handle 800-Mbytes/s reads and writes with a storage capacity to 32 Tbytes.
The ability to manipulate this information is coming in part from PXI modules that make use of FPGA technology, such as the NI FlexRIO series and the recently introduced GX3500 from Geotest—Marvin Test Systems. These modules, which use adapter cards for signal conditioning and preprocessing, allow test engineers to perform hardware-based manipulation of data that is beyond the capacity of system CPUs.
Software-based signal processing is not far behind, however. The PXISA (PXI Systems Alliance) recently released the PXImc hardware and software specifications that will enable developers to implement multicomputing structures in PXI that leverage PXIe. Modules should start becoming available in 2010 that will allow software processing to multiply its performance in a PXI system.
PXI’s continual improvement appears even among humble yet critical signal-switching modules. “In today’s world, all signals are demanding greater bandwidth,” said Walt Strickler, VP of business development for switching solutions at Gigatronics. “As a result, there continue to be advances in the PXI platform. In the past, for instance, we would shoot for a 1-MHz bandwidth on a switching card, but today, 10 MHz is more typical, and we are seeing some at 100 MHz.”
RF highlights PXI’s expansion
This ability of the PXI community to keep pushing the envelope of possibilities is nowhere more evident than in RF test. “It was once viewed that you could not possibly put quality RF instrumentation on PXI,” said Tim Carey, PXI product manager at Aeroflex. “Now, that view has been knocked over.”
Recent PXI releases in the RF space tell the tale. Aeroflex’s 3026C 6-GHz RF signal generator raised the bar on RF output power from its prior limit of 1 dBm to a robust 17 dBm. Phase Matrix released a family of RF downconverters capable of operating at frequencies to 26.5 GHz. RF switching has also taken PXI into frequency ranges unimaginable only a few years ago. The 40-78x PXI microwave switch family from Pickering Interfaces, for example, handles signals to 65 GHz.
All this capability has arisen despite what critics point to as PXI’s limitations on space and power. Not that these constraints aren’t real. “It’s a constant challenge,” said Geotest’s senior product marketing manager Mike Dewey. “We can put in the functionality but then bump against limits in power draw, heat dissipation, and the like.” But the constraints are not as insurmountable as they might first appear. “You have to get more clever and use things such as enhanced cooling,” explained Dewey.
The electrical noise inherent in a backplane-based architecture is another apparent limitation that good engineering is resolving. “We have to design for the noise, because we cannot control what connects to the backplane,” said Aeroflex’s Carey. “So, we need high levels of screening, and [we need to] put the RF on a separate module with its own bus. But rack-and-stack instruments face the same issues. The only difference is the proximity of the instruments.”
“The key to handling the noise in PXI is to use best practices in the design,” said Gigatronics’ Strickler. He added that designers must “separate chassis and control grounds from the signal ground, use multilayer boards, and treat signals as transmission lines, matching impedance and stub lengths.”
Constraints foster innovation
Facing challenges such as noise and power restrictions may, in fact, be part of PXI’s secret for continued enhancement. “Having these constraints can lead to very elegant design,” said Aeroflex’s Carey. “People used to think that high-quality RF needed large, heavy, expensive systems, but a lot of the size and weight arose because the engineering was not constrained. To put things into PXI, someone had to be clever, so we have ended up with designs that are efficient, lean, and not power hogs. Now, it’s the capability of the transducer that is the hard limiter to what’s possible.”
The ever-shrinking dimensions of electronic systems that mobile devices exemplify is helping PXI developers overcome these restrictions, as well. “The global move toward miniaturization has been a boon for PXI, letting us pack in more capability,” said NI’s Friedman. “A PXI module is gigantic compared to an iPhone.”
Counter to intuition, the worldwide economic recession is also contributing to PXI’s expansion, as semiconductor and device manufacturing turns to PXI for production test solutions. “Manufacturers have had to take a hard look at capital costs,” said Geotest’s Dewey. “They used to be able to spend half a million dollars on a tester because of production volume. Now, they’re looking to reduce costs by orders of magnitude, and PXI’s technology has evolved to where it can handle the testing.”
Manufacturers are also looking at the flexibility that PXI’s modular architecture allows. “More and more, we’re seeing a 'boutique’ view of how testing is done,” said Dewey. “Manufacturers are screening devices differently for various customers, so production test runs for a given configuration are lower in volume.” The ability of PXI systems to be rapidly customized and reconfigured supports this new test paradigm.
Production test pushing PXI
The rise of production test as a market for PXI has fostered a flurry of innovation as PXI vendors work to achieve the required performance levels. In fact, the industry has seen a rise in the number of PXI modules and systems specifically targeting manufacturing test. One recent example is NI’s Semiconductor Suite, which includes nine modules ranging from source-measurement units to vector signal analyzers.
This pushing against the performance envelope shows no signs of slowing, much less stopping. To address the needs of wireless LAN device testing, which requires 5.8-GHz signal switching, Gigatronics is exploring new options to replace board-mounted electromechanical switches, which only provide 3- to 4-GHz bandwidth. “We need higher performance switches in smaller packages,” said Strickler, “and [we] expect to have them in the next few years.”
Instrumentation is also increasing its bandwidth. NI and Tektronix recently announced a joint effort to develop a PXI digitizer module that can achieve sample rates beyond 10 Gsamples/s with a signal bandwidth in excess of 3 GHz. The companies expect to release the module during 2010.
This relentless push against the boundaries has paid off handsomely for PXI. As Gigatronics’ Strickler pointed out, “In a down economy, an organization like the PXISA would normally decline, but it is continuing to grow as the number of people doing products on PXI increases. This is a clear validation of PXI’s benefits.” In fact, the PXISA says that industry analyst Frost & Sullivan confirms the upward trend, predicting a compound annual growth rate of 17.6% through 2014 for PXI systems (Ref. 1).
The ability to maintain the push will ultimately determine how PXI fares against emerging modular instrumentation rivals such as LXI. While each technology has its advantages in specific applications, it is the continued improvement in performance that will determine PXI’s long-term fate. “PXI cannot survive being an also-ran in terms of performance,” said Aeroflex’s Carey. Given the history of innovation in its first decade, however, PXI has no worries there.
| Reference |
|
|
For further reading |
| Quinnell, Richard A., “PXI system tests MEMS products,” PXI Test Report, Test & Measurement World, November 2009. p. 45. |
No related content found.
- 0 rated items found.
Datasheets.com Electronic Parts & Inventory Search
185 million searchable parts
- Part Number
- Description
- Inventory
- Products
- Manufacturers
View All Webcasts
