Driving Down the Size of Test with a One-Slot PXI Vector Network Analyzer

1. Introduction
2. Customer Point of View: Emerging Needs
3. Keysight Point of View: Driving Down the Size of Test
4. Conclusion
5. Related Information

As the industry leader in vector network analysis, we maintain ongoing contact with a wide range of leading-edge customers. Over the past several years, a pattern has emerged. First, many needed vector network analysis with four-port capability. Then, a variety of next-generation products required eight-port measurements—and we responded. The next needed 16-port capability—and several asked us, “You know what’s coming next, right?” Yes, and we’re ready for applications that need up to 32 ports.

Along with this trend, many of our customers also need to drive down the size of test with more capability per cubic inch in their test stations. This is a subset of the larger need to drive down the cost of test to help ensure ongoing profitability as prices erode in wireless communications or as business models change in aerospace and defense.

Across these industries and others, more system developers are choosing to shift a growing percentage of their capital-equipment budget to modular measurement hardware. Whether they opt for an all-modular architecture or choose a hybrid modular/box-instrument approach, system size will shrink. Although this won’t necessarily reduce up-front costs, many expect the long-term cost of ownership to decline.

For us, success depends on the ability to meet these needs while coping with the increasing complexity of silicon wafers, wireless devices, advanced radar systems, and more, that continue to pack more capability into less space. These intersecting requirements have inspired Keysight to create one of our most remarkable achievements in vector network analysis: the M937XA Series PXIe VNAs.

Our PXI vector network analyzers are full two-port VNAs that fit in just one slot (Figure 1). They perform fast, accurate measurements and reduce the cost of test by enabling simultaneous characterization of many devices—two-port or multi-port—using a single PXI chassis. .

Figure 1: A two-port PXI VNA that fits in just one slot is a remarkable achievement that satisfies present and evolving requirements.

From our vantage point as the leader in network analysis, we’re able to keep tabs on future needs as they begin to take shape. Recently, three major themes have emerged:

• The need to test highly complex devices in much less time without sacrificing accuracy
• The need to test multiple devices—and test in greater numbers—at a single test station
• The need to reduce the size of the test stations used to test multiple wafer sites or complex devices

Three types of user scenarios illustrate these needs and the desired solutions: implementing a multi-function tester, testing multiple devices or sites, and testing complex multi-port devices.

Many of our customers have implemented multi-function testers within a single PXI chassis. As the chassis fills up, fewer slots are available to incorporate VNA capability. A one-slot PXI VNA is ideal for this situation—and that’s why we endeavored to create our unique solution.

On the production line or in a wafer fab, there is a growing need to test multiple devices or multiple wafer sites at a single test station. Examples include cell phone handsets, military radios and increasingly dense silicon wafers. In these situations, one of the key needs is reducing the overall size of the test solution. The ability to install multiple two-port PXI VNAs in a single chassis provides a tremendous space reduction when compared to using multiple benchtop analyzers on the production line or as part of a probing station (Figure 2).

Figure 2: Adding two-port PXI VNA modules to an existing test station enables powerful device characterization without expanding system height or footprint.

As devices become increasingly complex, there is a need to easily characterize a full set of S-parameters on a large number of ports—8, 16, 24, or more. Examples include smart antennas and phased-array transceiver (TRx) modules. For these complex devices, the ideal solution must be both flexible and space-efficient. For example, a single chassis containing sixteen two-port VNAs could be configured as eight four-port VNAs, four eight-port VNAs or one 32-port VNA.

Until very recently, when limited VNA capabilities became available in the PXI form factor, the default frame of reference—for us and our customers—was benchtop instruments. Over the years we have enhanced many of our benchtop VNAs with capabilities that increased the number of ports that can be measured simultaneously. The downside: solutions that require more than eight ports often become unwieldy in terms of size, cabling, complexity and power consumption.

Our PXI VNA is a giant leap forward in a device that is just 3.75” by 7” by 0.75” (95 x 178 x 19 mm), which is roughly the size of two slices of bread (Figure 3). Within that single-slot package, we’re providing a tremendous amount of performance:

• Sweep speed: 28 to 33 msec across 401 points
• Dynamic range: > 116 dB at 9 GHz, > 98 dB at 20 GHz
• Trace noise: < 0.001 dB
• Stability (typical): 0.005 dB/°C.

Figure 3: Adding two-port PXI VNA modules to an existing test station enables powerful device characterization without expanding system height or footprint.

The foundation of that performance is a combination of proven, high-performance components and a pair of high-density circuit boards.

Six models are available, reaching from 300 kHz to 4, 6.5, 9, 14, 20 or 26.5 GHz (Figure 4). This enables our customers to buy the frequency coverage they need now, and we’ve designed the PXI VNA to make it easy to upgrade frequency coverage in the future.

Figure 4: The family provides consistent speed and performance across a choice of six frequency ranges.

The Keysight PXI VNAs also provide a graphical user interface that shares the familiar look-and-feel of the benchtop PNA family. This eases the transition to PXI for benchtop users developing solutions in R&D or manufacturing.

Figure 5: The PXI VNA interface guides test engineers using a similar look and feel as Keysight's popular PNA family of network analyzers.

Of course, calibration is the other key to accurate, repeatable S-parameter characterization. Our PXI VNA uses the same measurement science and the same proven, trusted calibration routines found in our PNA family of microwave network analyzers: through-reflection-line (TRL), short-open-load-through (SOLT) and all of the other specialized calibration routines. In addition, it offers guided calibrations and full multi-port calibration capability, and is compatible with mechanical calibration kits as well as our electronic calibration (ECal) kits.

All these capabilities can be configured to satisfy the range of scenarios described in the preceding section: a one-slot VNA for a single-chassis multi-function tester, up to eight two-port VNAs in a single chassis, or cascaded modules that create a flexible combination of multi-port VNAs in a single chassis.

Figure 6: This versatile multi-port configuration uses eight two-port PXI VNAs in a single chassis.

Figure 7: This example multi-site configuration includes a quartet of independent four-port PXI VNAs in a single chassis.

Measurement functionality is scalable through a range of software options. At introduction, optional capabilities include time-domain analysis, N-port calibrated measurement, and advanced fixture-simulator capabilities.

Since the 1960s, Keysight has been the industry leader in vector network analysis. Today, we’re sustaining our leading position by offering customers meaningful alternatives in price, performance and capability. With our first PXI VNA, we offer choices in form factor and flexibility that address emerging needs in aerospace, defense, wireless communications, electronic devices, and more.

Whether our customers are testing active or passive devices, the right mix of speed and performance gives them a meaningful edge in today’s most highly competitive industries. In R&D, our VNAs provide a level of measurement integrity that helps developers transform deeper understanding into better designs. On the production line, our VNAs provide the throughput and repeatability—and now footprint—needed to transform undifferentiated parts into competitive components. Across the customer’s lifecycle, the common measurement science—hardware, software and applications—used across our solutions ensures fully specified products, whether they need to optimize for performance or throughput.

Every Keysight VNA is the ultimate expression of our expertise in linear and nonlinear device characterization. On the bench, in a rack or in the field, we help our customers gain deeper confidence.

Keysight is a global electronic measurement technology and market leader helping to transform its customers’ measurement experience through innovation in wireless, modular, and software solutions. Keysight provides electronic measurement instruments and systems and related software, software design tools and services used in the design, development, manufacture, installation, deployment and operation of electronic equipment. Information about Keysight is available at www.keysight.com.