Recent vector network and signal analyzer introductions show what a significant competitor the PXI platform is becoming in the RF/microwave test arena—with applicability extending from the Wi-Fi frequencies up to 26.5 GHz. But box instrument makers are not ceding the field to their PXI counterparts.
Nevertheless, a recent report from Frost & Sullivan found that OEMs are adopting PXI-based instrumentation to take advantage of the PXI platform’s measurement speed, small footprint, low power consumption, and flexibility. The market-research firm said PXI reduces the time to market and overall cost of tests—especially in the wireless-communications space.
According to the report, titled “PXI Market to Change the Face of the Test and Measurement Industry,” the PXI market earned revenues of $563.3 million in 2013, and the firm estimates that PXI sales will reach $1.75 billion by 2020.
“Besides the uptake in RF wireless communications, the global PXI market will get a leg up from new programs in aerospace and defense and integration of wireless technologies in the industrial and consumer electronics industries,” said Frost & Sullivan test and measurement industry director Jessy Cavazos. “Additionally, it is finding opportunities in the semiconductor automatic test equipment market.”
However, test engineers retain affection for the box instruments they have used effectively for decades—a fact that is slowing down the transition to PXI test systems. But Frost & Sullivan predicted that a new generation of test engineers more comfortable with computers will mitigate this challenge.
“Meanwhile, the more complex process of integrating PXI test systems, in comparison to rack-and-stack test systems, can be a challenge for customers,” said Cavazos. “To ease the process of integration, market participants across the globe are offering different levels of integration services and tools that enable customers to assemble PXI test systems quickly with minimal effort.”
Courtesy of National Instruments
PXI instruments debut
At NIWeek in August, National Instruments introduced its NI PXIe-5668R high-performance vector signal analyzer (VSA) and spectrum analyzer, which operates at up to 26.5 GHz with 765 MHz of analysis bandwidth. It offers a -165-dBm/Hz average noise floor at 1 GHz and -129-dBc/Hz phase noise at a 10-kHz offset (800-MHz center frequency). The new VSA complements other recently introduced software-designed instruments, including a 14-bit, 250-MS/s, 300-MHz, eight-channel oscilloscope; a 12.5-Gb/s, 8-TX/8-RX lane high-speed serial instrument; and a 12-bit, 2-GS/s, 2-GHz intermediate-frequency digitizer (Figure 1).
Speaking at NIWeek, Nisha Ganwani, senior marketing manager, said, “The VSA features a user-programmable FPGA, making it fully software-designed. The great thing about being able to program the FPGA is that users can extend the instrument’s capabilities for new and innovative measurements.”
Prathima Bommakanti, industry analyst for measurement and instrumentation at Frost & Sullivan, was similarly enthusiastic about providing a user-programmable FPGA, which can lead to “astounding benefits for the customer.” She said that enabling users to turn the instrument into whatever they need represents a paradigm shift in an industry in which products have been defined by the vendor as opposed to the customer.
Ganwani noted that communications network providers and government agencies like the FCC routinely monitor the radio spectrum to identify harmful sources of interference. She presented a specific example of a wideband Wi-Fi signal with an interfering signal fading in and out. “It is difficult to identify the source of the interference signal with a traditional spectrum analyzer,” she said. “This is where a software-designed instrument can be repurposed to quickly debug the issue.”
Ganwani described downloading to the analyzer, via LabVIEW, a real-time spectrum-analysis capability that could perform 2 million FFTs per second and overlay the data onto a single graph to monitor frequency and intensity over time—quickly showing that the interfering signal was a chirp at about 5.5 GHz.
Keysight Technologies makes a variety of instrument form factors, including traditional bench, modular, and portable. The goal, said Mario Narduzzi, marketing manager for the company’s Modular Solutions Division, is to remove the “one size fits all” constraints and allow customers to select the best test asset independent of form factor—thereby increasing efficiency, with simulation and measurement results correlating across the product lifecycle.
Courtesy of Keysight Technologies
Recent efforts have resulted in the introduction in September of the M937xA series of one-slot PXI vector network analyzers (VNAs), which covers 300 kHz up to 26.5 GHz (Figure 2).
John Swanstrom, application engineer at Keysight’s Component Test Division, said the new single-slot VNA traces its lineage back to the Model 8410A in 1967. The new PXI VNA complements a Keysight VNA line that extends from the FieldFox handheld instrument to the high-end PNA.
Enabling technology includes a dense 24-layer RF circuit board and proprietary RF circuits designed by Keysight’s technology center that pack high performance into small packages. The PXI instrument, Swanstrom said, shares the same measurement science, calibration science, and soft front-panel interface of the high-end PNA. The instrument, he said, addresses the increasing need for multisite and multiport measurements—it enables up to 32 ports in a single PXI chassis. And when space is at a premium in an existing system, full two-port VNA capability with S-parameters can be added to an existing chassis that has just one open slot (Figure 2).
Concurrent with launching the single-slot PXI VNA, Keysight also introduced a PXI reference solution for RF power amplifier (PA) characterization and test. Narduzzi defined a reference solution as a combination of hardware and software enabling users to rapidly evaluate a test configuration for a specific test application. Other recently introduced reference solutions address LTE-Advanced and multichannel antenna calibration.
The new PA reference solution—which performs S-parameter, harmonic distortion, power, and demodulation measurements—enables rapid, full characterization of next-generation power amplifier modules, such as a power amplifier-duplexer (PAD). The reference solution is optimized for high throughput and highly accurate measurement quality.
“We created the PXI reference solution for RF power amplifier characterization and test because customers told us that full characterization of PAD-type devices is critical to their success,” said Narduzzi. “Proven, robust digital predistortion algorithms, with open- and closed-loop measurements, deliver the best performance of any PA characterization test solution in the industry.”
Also in September, Keysight introduced a PXIe signal analyzer. “We’ve expanded the Keysight X-Series with the CXA-m, a PXIe signal analyzer that offers fully specified performance up to 26.5 GHz,” said Cherisa Kmetovicz, product manager at the company’s Microwave & Communications Division. “It handles RF and microwave signals in four slots, and customers can leverage their existing code.”
The new instrument targets general-purpose as well as military/aerospace applications—for the latter, it helps meet mandates to use modular open-system architectures for military programs. Kmetovicz said the CXA-m minimizes time to deployment via its familiar X-Series user interface, which simplifies the transition from box instruments to PXI.
As Cavazos from Frost & Sullivan noted, PXI is gaining traction in the semiconductor automatic test equipment market as well as the RF/microwave space. Of course, the two are not mutually exclusive. Luke Schreier, senior group manager of test systems at NI, said the mobile revolution has driven requirements for higher performance wireless standards, which presents challenges for semiconductor companies. Design engineers want high performance while production engineers want lower test times.
It’s possible to have both, Schreier said, as Chris N. White, product marketing manager at NI, showed in an NIWeek demonstration of the test of a 16-bit digital-to-analog converter having a sampling rate up to 2.5 GS/s—a device commonly used in wideband communications—driving both NI’s new PXI VSA and a traditional box VNA. Both instruments, he said, can accurately characterize the device with respect to parameters like ACPR, but the PXI version operates 14.4 times faster. The PXI approach, explained Ganwani, can serve in the development process and ease the correlation between characterization and production while cutting test times in production.
While the NIWeek demonstrations began with lab applications and moved toward production, LitePoint emphasized lab applications of the PXI platform with the July launch of its z8653 VSA for the development testing of high-bandwidth wireless components used in smartphones and tablets—including 802.11ac Wi-Fi Wave 2.
Chris Ziomek, general manager of LitePoint’s Design Test Division, said at the time of the introduction, “With Wave 2 components in the R&D pipeline now, the z8653 provides development engineers uncompromised measurement capabilities to test these complex wireless components while meeting aggressive development cost and time-to-market goals.”
Courtesy of ADLINK Technology
He added, “This instrument will find application not only in design verification, but also in R&D engineering groups developing the next generation of connectivity and cellular technologies.”
In support of RF/microwave applications, ADLINK Technology in August introduced its PXIe-3985 high-performance 3U PXI Express (PXIe) embedded controller (Figure 3), equipped with the quad-core fourth-generation Intel Core i7-4700EQ processor and operating at up to 3.4-GHz clock frequency (in single-core Turbo Boost mode). The company said the PXIe-3985 is suitable for applications requiring intensive data analysis or processing and high-speed data streaming, such as in wireless, radar, or RF testing environments.
Box instruments hold on
Of course, box instruments aren’t ceding the field to PXI implementations. For example, Rohde & Schwarz in September introduced the R&S ZND VNA, which is part of the company’s low-cost Value Instruments portfolio. The ZND features two test ports, and the base unit is designed for unidirectional measurements from 100 kHz to 4.5 GHz. The frequency range can be extended to 8.5 GHz, and the instrument can be equipped for bidirectional measurements at 4.5 GHz or 8.5 GHz.
The R&S ZND is suitable for production-line measurements such as characterization of passive mobile-phone components. The easy-to-operate instrument also is appropriate for training purposes. The analyzer’s 30-cm touch screen and intuitive user interface make it easy to configure measurements and analyze results. All instrument functions are accessible in no more than three operating steps via the soft panel.
Courtesy of Keysight Technologies
And Keysight Technologies has been focusing on box instruments as well as PXI versions. In the signal-analysis space, the company introduced in October what Joe Rickert, R&D manager for the company’s Microwave & Communications Division, called the “new X-Series flagship”—the N9040B UXA signal analyzer (Figure 4). Three models offer up to 26.5-GHz performance with 510-MHz analysis bandwidth. The instrument, he said, includes a 14.1-inch touch screen and a streamlined UI.
As does the company’s CXA-m PXI analyzer, the benchtop UXA can serve commercial communications as well as aerospace and defense applications. For the latter, Rickert said, the instrument targets radar, electronic-warfare, and high-performance satellite systems. For wireless R&D applications, the instrument can help developers contend with emerging bandwidth-hungry standards and deal with intermittent and interfering signals. Other wide-bandwidth applications are those incorporating the DOCSIS 3.1 standard.
Key specifications, he said, include better than 0.7-dB IF frequency response and an SFDR better than 75 dB across the 510-MHz analysis bandwidth as well as a 20-dB improvement in phase noise at a 10-kHz offset. Enabling technologies, he said, consist of a new proprietary ADC, a new wide-bandwidth front end, a new proprietary DAC, and a direct-digital-synthesis-based local oscillator that reduces spurs and phase noise.
Of course, when looking to purchase an analyzer, PXI and traditional box instruments aren’t your only choice. For example, Copper Mountain Technologies makes a line of USB VNAs, including the 19-inch chassis-mounted Planar 804/1, which operates from 100 kHz to 8 GHz; the compact Planar 5048, which operates from 20 kHz to 4.8 GHz; and the compact Planar R140 reflectometer, which measures S11 from 85 MHz to 14 GHz.
For design and development applications, the instruments facilitate the storage of data and setup information on the users’ PCs. For production, they offer low cost and a small footprint. With no internal memory, they facilitate data security in military and aerospace applications.
As this article goes to print, companies are gearing up to present at Autotest 2014.1 Undoubtedly, many will be highlighting RF/microwave instruments, applications, and technologies with a military/aerospace slant, which we will cover in an upcoming issue.
Nelson, R., “AUTOTEST spans legacy replacement to new systems,” EE-Evaluation Engineering, September 2014, pp. 14-20.
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