Officials at the Department of Defense (DoD) continue to push the useful lifetime of military and aerospace systems. For instance, the Air Force Times recently reported that the Air Force extended the life expectancy of the F-16 aircraft from 8,000 flight hours to 12,000 hours. Situations like this one are forcing test and measurement companies to contend with new technology insertion in legacy systems; the corollary to this: designers and manufacturers must also take a closer look at the acquisition process in order to stay ahead of the game.

Much like in other military electronics applications, designers of test and measurement systems face ongoing obsolescence and technology insertion challenges as the users of their equipment continue to demand the latest in commercial technology and that it be compatible with technology that is sometimes more than a decade old – providing the challenge for the test engineer.

The reality is that “support of legacy test systems is always a concern,” says Darren McCarthy, A&D [aerospace & defense] technical marketing manager at Rohde & Schwarz USA in Beaverton, Oregon. “Especially so when you are dealing with new technology insertion and customers want to leverage commercial technology as much as possible, whether it is IoT, 4G/LTE, or 5G for radio communications, or even just a new wideband waveform.”

McCarthy points to an example, noting that “Customers are always looking for how they can add this new technology while still supporting the existing radios that they have. This might be an add-on or a new waveform added to a software-defined radio (SDR) that is currently supported.”

One major aspect of extending the useful life of such systems is ensuring that the military user finds the right vendor as they “are always looking for vendors to provide extended life COTS [commercial off-the-shelf] instrumentation,” says Adam Foster, principal marketing manager at National Instruments (NI) in Austin, Texas. “They’ve obviously been big adopters of COTS; the longer that they can hold onto legacy parts or legacy systems, they tend to be the ones who will call us up and talk to their account managers and ask life cycle management questions.”

Common questions, Foster says, include “How long is this product going to be around?” and “Is there any way that I can do a lifetime buy of it for certain things?”

The “life cycle of these test systems are 15, 20, 30 years. They’re looking to salvage form, fit, and function of the instrumentation. Anything they can do to mitigate or reduce the cost of revalidating a test system is an important one,” Foster adds.

Even with this reality, users are expecting the latest, greatest technology to be inserted into their aging systems. That expectation includes an “interest in reducing rack space,” McCarthy says. “The R&S FPS is a two-rack unit high, high-performance spectrum analyzer that has the entire legacy support as well as modern functionality.”

Figure 1: Rohde & Schwarz’s SGS and SGU series products. Photo courtesy of Rohde & Schwarz.

“The R&S SGS/SGU and R&S SGT series signal generator products are one rack unit; half-width products that can cover up to 40 gigahertz CW and vector signal generation capability, respectively,” McCarthy adds (see Figure 1). “These enable the flexibility of reducing rack space as well as having this legacy support for new technology insertion.”

A closer look at DoD acquisitions: a smart move

Legacy military and aerospace systems compel companies to take a closer look at the acquisition process; thorough knowledge of acquisitions will give them a deeper understanding of where the market is heading. Ultimately the market is difficult to predict, as some segments have seen a flat market over the past few years, while other companies have enjoyed a bit of an upturn.

Overall, “the U.S. A&D business, in general, has been at about a two or three percent growth rate,” McCarthy states. “But if you look at things like the breakout that A&D spend, the RTD&E, which is the test and evaluation part of the A&D spend, that’s up nearly 16 percent. This bodes well for companies positioned to help with technology insertion.”

Other driving factors in this area, McCarthy says, include “spectrum auctions, which are moving into the spectrum of installed radio and radar systems. This is causing reassessment and even redesign of systems to new frequencies. There are also new technology insertions, specifically in commercial satellite. The NewSpace technologies and the next-gen satellites tend to use a lot of the aerospace and defense infrastructure, launch vehicles, and monitoring stations.

“These are indirectly driving some aerospace and defense investments including the use of better component technologies like GaN [gallium nitride], low-phase noise systems design, and faster test processes to handle the volume of test,” he adds.

In addition to that, “We also see moving away from older technologies like parallel digital lines to high-speed serial lines,” Foster says. There is a definite shift of “some investments in that sense over to higher performance and cutting-edge RF [radio frequency], and SDRs, and then high-speed serial digital protocols.”

A closer look at the acquisition process will help companies to move in a certain direction that actually allows them to position themselves with the right product line. According to McCarthy, “If you look at the budget for operations and maintenance (O&M) those two, year over year, have been up substantially, about six and 22 percent, respectively.”

Cost is the driving factor to any decision made when it comes to managing the lifecycle of military and aerospace systems. “On the software side, these customers really appreciate anything that vendors can do to make sure that the software doesn’t have to be re-validated,” Foster says. “I think it’s upwards of $200,000 just for them to open up a test program set, change one value, then close that test program set back down, and ship it back out to their test system. It’s super-expensive for them to do that, and that’s one of the things that we take really seriously when it comes to our software.”

PXI standard

Along with lower costs, users of test equipment also want more modularity, a desire that is moving them toward the PXI standard and away from VXI.

“We are seeing the trend for the legacy system shifting from VXI to the PXI standard,” points out Mike Tseng, senior program manager at Adlink Technology in San Jose, California. In fact, he says, “the military and aerospace customers are looking for way to adapt into more modular concepts.”

PXI has “been around for 20 years now,” Foster adds. “The aerospace and defense and government agencies have definitely always been keen on using modular instrumentation.”

The idea is to stay “modular, with multi-slot chassis and high computing controller technology with the CompactPCI form factor for ruggedness and with integrated timing and synchronization capabilities,” Tseng says. “PXIe is a COTS product that can be configured to any modern computer and has rich software support.“

The standard speaks for itself as it already has “over 60 active members with over 1500-plus PXI/PXIe modules, many of them designed specifically for ATE [automatic test equipment] aaplications,” Tseng adds. “The PXIe standard also coupled with higher throughput bandwidth as its backplane leveraged the PCIe design and current in the transition to GEN 3 with up to 24 GB throughput; the GEN 4 spec has just been defined.”

To a certain extent, VXI is becoming less and less common: “There are a few programs that still use it, just because of where they are and that’s the best thing for them, but for the most part, everybody’s switched over to PXI,” Foster asserts.

“VXI and PXI/PXIe are directly competing standards,” Tseng points out. “We are seeing much stronger growth in PXI over the years and other test standards like PXIe and AXIe (up to 100G bandwidth support) being used as multiple platforms for some ATE applications.”

The pros of using PXI instruments range widely: “The power consumption of PXI is a lot lower compared with older technologies,” Foster says. “Then, you continue to reap the benefits of higher performance processing, and latest and greatest FPGAs [field-programmable gate arrays] for things like synthetic instrumentation. You can actually use an FPGA to emulate the behavior of a legacy instrument. You can come over to PXI, and you can actually use a PXI instrument that has an FPGA on it. You can write custom algorithms to actually emulate the behavior of that old instrument.”

Using tools to extend the life cycle of a system is the end goal here. With FGPAs, “We use FPGA programming to put some – I would consider them to be old-school – legacy trigger types where you used to trigger off of some kind of riding edge or falling edge or some certain pattern that you were looking for in the signal,” Foster adds. “That’s considered ‘legacy,’ so if you go and try to buy an oscilloscope these days, that type of trigger’s not going to be available off the shelf. With the power of an FPGA you can actually write a program to build that trigger yourself. That extends the life cycle and gives these program managers additional time for the test system to be around, and you get that same function out of it, which is a big benefit for them.”

PXI becomes the go-to standard because “There’s no longer innovation in VXI. If you’ve got a test system that’s built off of that, you know, it’s only a matter of time before you will not be able to find the majority of that instrumentation anymore.”

For the new challenges that arise in the RF world, NI’s engineers developed the PXIe-5840 module that includes a 6.5 GHz RF vector signal generator into a two-slot PXI Express module. (See Figure 2)

Figure 2: NI’s PXIe-5840 also includes 6.5 GHz vector signal analyzer, FPGA, and high-speed serial and parallel digital interfaces. Photo courtesy of National Instruments.

“The main point I’m getting at there is that software really is a key element in a PXI system,” Foster says. “The system is built around the software, so to speak, when it comes to PXI. What that gives you is flexibility to change the functionality. As you need to insert technology, software’s going be one of the biggest ways you overcome those challenges.”

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