June Special Report: RF/Microwave Test

Vendors and partners weigh in on trends, challenges, and customer demands in RF/microwave testing (including 5G), as well as what new solutions are on the market.

Header Option 1As the basis for telecommunications services, radio frequency (RF) energy enabled near-instant transmission and reception of electronic signals from one source to another—across distances that span millimeters to thousands of miles. As the technology has improved, so has that speed and reliability of those signals, and it’s largely thanks to the work being done by engineers in the field of RF/microwave test. The onset of 5G is bound to drive demand for advanced testing, but telecommunications isn’t the only application area for RF/microwave energy. Microwave ovens, radar, industrial heating and sealing, and RF components are other areas where RF/microwave testing comes into play.

We at Evaluation Engineering gathered input from a variety of electronic test & measurement solution providers to get their thoughts on trends in RF/microwave testing and areas of focus, 5G, and what new products/solutions are now on the market. Read on to see what they told us.

Thermal RF/microwave testing

As a subset of RF/microwave testing, thermal testing is an important part of building any electronic system when it must be highly reliable. Better methods, better automation, and benchtop accessibility can greatly streamline the process. Testing at the component level as well as at the system testing all fit into the scheme of making reliable RF and microwave products in a way that provides traceability.

Total Temp Technologies’ Model SD288 Thermal PlatformTotal Temp Technologies’ Model SD288 Thermal PlatformAs much we may desire to have faster, better and easier thermal testing, we can’t bend the laws of physics or have a test programming wizard button that makes the perfect test profile for a complicated electronic system. Fortunately, we can use the laws of physics to our advantage and easily make better testing choices with the help of the best automation features in a temperature controller.

For example, temperature cycling a device that has circuit boards, active power devices, a heat sink, and some kind of enclosure might be a challenge to make a fast and effective temperature profile to test the product.

“By having the controller monitor more than one point, it can easily be determined that everything under test is within the required temperature range and not blindly moving on to the next temperature setpoint without assuring temperature is actually achieved plus settling time if needed,” explained Jon Booher, chief technology officer at San Diego, CA-based Total Temp Technologies, a provider of thermal test solutions. “Advanced temperature control algorithms can easily allow controlled amounts of overshoot to get the temperatures into uniformity more quickly. Local alarm indications, email, or text alerts can also make notifications to the technician for end-of-test or something going out-of-bounds, and easy-to-program front panel or remote functionality with LabVIEW or C++ drivers can coordinate the testing with other instruments.”

To best keep the laws of thermodynamics on your side, benchtop thermal test systems can now combine the effects of conduction plus convection under unified control to maximize control over setpoint temperatures and minimize transition and stabilization times for faster testing.

Total Temp Technologies’ traditional Benchtop Temperature Chamber.Total Temp Technologies’ traditional Benchtop Temperature Chamber.“People often reflexively think of a chamber first when it comes to benchtop thermal testing,” Booher said. “Especially for flat microwave and RF packages, quite often a thermal platform with its tremendous heat transfer capabilities and accessibility while under test can greatly outperform the slower heat transfer of a standard convection chamber.”

Due to their complex geometries, some devices are just not optimal for testing on a thermal platform.  In many cases, a custom fixture is a good solution, in other cases a combination of convection and conduction can provide a better solution.

“Still, for many microwave and RF products, a traditional temperature chamber is the best solution,” Booher added. “The convenient lab automation features and advanced temperature control features of the TotalTemp custom benchtop test chambers will give you the choices to best perform thermal testing.”

Total Temp Technologies recently introduced its dual-mode Hybrid Benchtop Temperature Test Chamber, which allows faster and more effective thermal testing of devices, regardless of different heat capacity and active loads. Meanwhile, Total Temp’s product offering also features traditional benchtop temperature chambers, and thermal platforms with temperature ranges from -148 to 392 degrees Fahrenheit.

What’s trending?

What are vendors seeing as trends in the RF/microwave or 5G test area?

Rohde & Schwarz’ CMX500 Signaling Tester for 5G NR FR1 and FR2.Rohde & Schwarz’ CMX500 Signaling Tester for 5G NR FR1 and FR2.Mike Thorpe and Bryan Helmick, wireless device test product managers at Rohde & Schwarz USA: “In 2019, we have already seen a massive increase in 5G FR1 (400 MHz to 6 GHz) test requirements as all versions of 5G NR FR1 are being primed for deployment. Starting now and continuing beyond the year 2020, non-standalone (NSA) TDD and FDD, standalone (SA) TDD, and FDD will be the key technologies enabling the wide acceptance of 5G NR.”

Dr. Frank Kearney, director of engineering, Wireless Systems Group, Communications Business Unit at Analog Devices: “We are seeing the challenges of 5G falling into two buckets: sub-6GHz massive MIMO and mmWave (mmW) deployments. Both groupings are critical elements in the rollout of 5G, but while the short-term market focus is on sub-6GHz, 5G mmW is also starting to ramp up. We are seeing a marked year-over-year increase on mmW program activity from all our lead customers, mimicking the increasing pace of mmW auctions around the world. Based on U.S. mmW spectrum acquisition, costs have thus far been reasonable, which is promising for return on investment and capital expenditures for operators spending on mmW deployments in the next three to five years. The market sentiment has shifted from discussing whether there will be a market for mmW 5G to when it will happen in scale as rollouts move from localized fixed wireless access trials to the first handset deployments. Regarding test & measurement, suppliers already have their first generation of 5G instrumentation, which is comprised of both mmW and sub 6GHz, and now the next generation of equipment is being developed to focus on a combination of improved performance, wider bandwidths, cost optimization and future scalability.”

Erik Luther, vice president of X-Microwave: “When you weed through the hype about 5G, there are three pressing questions: How quickly will 5G below 6 GHz roll out in existing spectrum?; who will be the first to broadly deploy mmW for fixed wireless applications?; and will mmW ever be suitable (technically and economically) for mobile applications?”

AR RF/Microwave Instrumentation’s Model 350S1G6A Amplifier.AR RF/Microwave Instrumentation’s Model 350S1G6A Amplifier.Applications Engineering, AR RF/Microwave Instrumentation: “AR sees 5G and Wi-Fi products increasing over the next several years, and with them the need for RF amplifiers for component and end-product testing. The usage of wider bandwidths by 5G systems and need for highly linear amplifiers plays right into AR product offerings. AR’s U series amplifiers operate from 10 kHz to 1000 MHz, and the S-series S1G6 amplifiers across the 700MHz to 6GHz band, both providing robust performance. Like the U and S series amplifiers, AR’s W-series maintain AR’s signature linear, Class A design and ultra-wide bandwidths from 80 MHz to 1000 MHz, at a maximum power level of 10,000 Watts.”

Bob Stasonis, technical product specialist at Pickering Interfaces: “Our products and services provide the most benefit to customers as newer technology begins to solidify and plans are made for high volume production. This applies to 5G just as in other industries and we are looking at how manufacturers in 5G are planning their production test strategies and where signal switching systems can improve efficiencies in test.”

Roger Nichols, 5G program manager at Keysight Technologies: “Keysight has been involved in 5G since 2013 so it is exciting to see the actual rollout of the first production systems. Our legacy is helping engineers design, simulate, and measure the physical layer and of course the RF/microwave parts of that represent core challenges in 5G technology. While we now have a much broader scope of measuring from the physical layer up to the application layer, the RF/microwave facet of 5G represents new technological challenges. It is not news that millimeter-wave bands are going to move to the “mainstream” and much has been written about the need to make these measurements more accessible to a much wider engineering audience.”

Areas of focus

RF/microwave and 5G research spans the gamut from algorithm development to channel sounding. What specific areas are vendors focusing on?

AR RF/Microwave Instrumentation: “AR continues to maintain its focus on providing the most linear and robust wideband Class A amplifiers on the market. What this means to the customer is that they can be sure that an AR amp will provide the cleanest representation of their input signal. The highly linear class A design allows for the minimum amount of signal distortion during the amplification process. This allows researchers to focus on their research instead of overcoming test and measurement limitations. The instantaneous wideband and high-power design also allows users to test many of 5Gs numerous bands simultaneously with a single amp providing significant headroom.”

Sarah Yost, senior solutions marketing manager, and Chen Chang, semiconductor offering manager at National Instruments: "As NI has been involved in 5G wireless research for almost a decade, we are uniquely equipped to understand the needs of this next generation technology. Earlier this year, NI launched its Test UE offering for 5G lab and field trials, which features a fully 3GPP Release 15 non-standalone (NSA) compliant system capable of emulating the full operation of end-user devices or user equipment (UE)." 

Bob Stasonis, technical product specialist at Pickering Interfaces: “The modular nature of our products, including PXI, lends itself to adapting to our customer’s needs.  In addition, we partner with our customers to create new switching designs that are more in tune with their testing needs.”

Luther, X-Microwave: “We are focusing on the RF hardware side, specifically RF and microwave design. Commercially viable 5G is being driven by and driving more affordable high frequency components than have ever been commercially available before. You can find a surprising number of amplifiers, mixers, multipliers, and other components off-the shelf that cover frequencies to 70 GHz and beyond.”

Nichols, Keysight: “We are seeing the biggest demands in the areas of UE/device testing since the early build-out of networks means an increased demand for new 5G UE’s. We are also seeing significant scaling in RF/microwave component testing, as well as RF base-station manufacturing test requirements. It is exciting to see work from research to deployment and optimization and be in every part of that.”

Dr. Kearney, Analog Devices: “Wider bandwidths, higher frequencies and tougher performance specifications, coupled with a need to reduce power consumption, are pushing the requirements for sub-6GHz. From an algorithm perspective, we see the delivery of wideband DPD and GaN power amp (PA) charge trap correction as essential. While static performance criteria such as ACLR and EVM remain important, they must be augmented by robustness, stability and efficiency of implementation. While some aspects of static performance at 5G mmW are relaxed, there are specific new operational (beamforming) and efficiency (PA DPD) challenges that must be met. ADI has and is continuing to invest resources to solve those challenges to preempt market and customer requirements.”

Thorpe and Helmick, Rohde & Schwarz: “Because of the move towards mmW, we have been working hard to expand our measurement capabilities from conducted testing to over-the-air (OTA) testing that will play a major role in 5G. At R&S, we are involved in nearly all areas of 5G wireless device testing.  Protocol stack development, RF and Antenna design at FR1 and FR2 frequencies, data performance, device reliability, service & repair, production/manufacturing, conformance (PTCRB/GCF), compliance (CTIA/FCC/ETSI), and network operator related supplemental testing are all our specialties.”

A timeline for 5G rollout?

While 5G rollout has begun amid certain cellular service providers, its large-scale rollout appears to still be at least a year away. When do vendors estimate we’ll see widespread rollout of true 5G service?

AR RF/Microwave Instrumentation: “As with other periods in history, the large-scale rollout of a telecommunication system will take some time. Components throughout the entire system must be developed and tested. AR understands this need and is working to provide amplifiers and systems that will be needed to evaluate and qualify these new products.”

Dr. Kearney, Analog Devices: “We are seeing immediate activity from sub 6GHz, which already has commercial deployments in the U.S. and Korea, with Japan soon to follow, and with meaningful large-scale roll-outs expected from late 2020 into early 2021. While different aspects of the technology vary from region to region, we are seeing a convergence in the overall push from both technical and political drivers advancing the rollout of 5G.”

Thorpe and Helmick, Rohde & Schwarz: “Research & development and device launch/rollout is happening now. While the initial 5G NR coverage and features available to the average consumer might not make a big difference to user experience until 2020, network operators are also rolling out improvements in 4G standard to complement 5G. You can think of this as 4.9G, LTE-A-Pro eMBB. Consumers paying a premium as early adopters of 5G devices will not accept massive drops in data rates when 5G NR service is unavailable. Therefore, LTE-A Pro eMBB features like 7CC downlink, 2CC uplink Carrier Aggregation, 1024QAM downlink / 256QAM uplink modulation, and 8x4 downlink MIMO are all features deployed this year. In other words, 5G is pushing LTE to the limit, which will be something that the average consumer will notice in 2019. As 5G NR matures, there are very exciting times ahead for 5G NR + LTE-A-Pro.”

Nichols, Keysight: “5G rollouts will happen much like previous generations. They have started with leading edge operators who are willing to take some risk on the new technology to be first. These operators have started commercial services in limited geographic areas with a limited range of service. The previous four generations have rolled out in a similar manner. The rollouts will continue over the next two years with announcements of plans not just from those who have already started (stating they will add more geographic areas for coverage as well as expanding the types of services), but also operators who have not started production systems yet.  While I do not have specific estimates, one can see speculation from many parts of the industry. Ericsson, for example, has predicted that as many as 1 billion 5G connections will exist by the end of 2023.”

Stasonis, Pickering: “Our observations are that it does not seem like there is a strong consensus, although I have to believe that people embedded in this industry have a pretty fair idea as to what is going on and when. We are working with vendors creating 5G hardware, but because of their corporate policies, they are not sharing their rollout plans with us at this time.”

5G challenges in RF/microwave test

Before anything can be formally rolled out in 5G, there are many challenges to overcome in the area of RF/microwave testing. What do vendors see as the key challenges here for themselves, or customers?

AR RF/Microwave Instrumentation: “One of the most important challenges is power. The demand for more and more RF/microwave power has only increased as technology progresses. Power is relatively easy to deliver over a narrow frequency bandwidth. The drawback with this is that, for an industry or application with many possible frequency allocations such as 5G, customers would need multiple narrowband, high-power amps. AR has continued to push the boundaries of power over wide frequency bandwidths. AR’s S-series amplifiers provide continuous coverage from 0.7 – 6 GHz while delivering in excess of 500 Watts of CW power.”

Luther, X-Microwave: “Perhaps the most challenging aspect for many of our customers is the development of test fixtures, custom PCBs, and such that may be beyond the current in-house capabilities of the organization or test team. This includes the ability to work with chip and wire (DIE) based parts and very expensive high frequency connectors and cables.”

Randy L. Oltman, marketing and system applications manager, Instrumentation Market Group at Analog Devices: “The testing of devices for sub-6GHz looks a lot like the testing of sub-6GHz LTE devices and generations before. The biggest 5G Test & Measurement challenges ahead are almost all related to mmW. The most significant is the definition of an all-OTA (over-the-air) production test method for mobile devices. This is an area currently under study by many suppliers as conducted mode testing at mmW looks unworkable. An all-OTA production test is a significant change to established test methodologies challenging the existing norms of tester footprint, test throughput, and overall cost of test. Obviously, a significant part of a viable OTA tester is the quality of the mmW signal delivered at very high-power levels. ADI’s complete mmW portfolio provides unparalleled fidelity in signal chain solutions for OTA test.”

Infinite Electronics, via Pasternack subsidiary: “In order to implement multi-user MIMO (Mu-MIMO) and carrier aggregation, many modem chips are necessary along with a substantial amount of RF routing. Moreover, the use of such high-speed modems also leads to the use of high-speed digital interfaces that run at several Gbps. Though much of these new sub-6 GHz modem/radio/antennas would ideally be integrated, the sheer volume of RF/high-speed ports and pathways creates a substantial RF interconnect challenge during prototyping, testing, production, and even troubleshooting/maintenance.”

Keysight’s VXG Microwave Signal Generators.Keysight’s VXG Microwave Signal Generators.Nichols, Keysight: “The challenges include not just the higher frequencies—which mean more sophisticated simulation and measurement solutions, but also the companion of mmW—higher bandwidths. This means much faster baseband processing, adjacent channel measurement challenges, flatness (amplitude and phase) in the in-band response, and so on. At <6GHz, many challenges arise here—not just wider bandwidths for single-component carriers, but the added challenges of link-budget demands. Trials suggest that at 3.5GHz, the difference between up-link and down-link is greater than 16dB—this means more complex designs using sophisticated MIMO techniques and tremendous pressure on low-noise and low power-consumption designs. All need test solutions.”

Thorpe and Helmick, Rohde & Schwarz: “There are many challenges associated with 5G. One of the biggest challenges is the sheer flexibility. Features like subcarrier spacing (SCS), symbol duration, cyclic prefix duration, bandwidth, frequencies from 400 MHz to 43.5 GHz, and virtualized (core network) functions make 5G incredibly complex. In order to fully test 5G, the test equipment also needs to be incredibly flexible to reduce the need for dozens of different test solutions.”

Protecting 4G investments

Obviously, 5G is all the rage right now, and will be for years to come. But with the vast majority of us still operating on 4G—or even 3G—connectivity until the fifth generation of wireless communication is available, how are vendors protecting their investments in 4G test-and-measurement equipment?

Anritsu’s Model MT8000A Universal Wireless Test Set.Anritsu’s Model MT8000A Universal Wireless Test Set.Adnan Khan, senior business development manager at Anritsu Company: “5G components, devices, and systems must all be developed at an efficient price point, which places a great deal of pressure on keeping cost-of-test low. Fortunately, Anritsu’s 5G test portfolio has flexible platforms that have made it efficient to upgrade current solutions. This allows customers to protect their investment in existing test solutions and upgrade to 5G NR support via software in most cases. For example, we have developed 5G NR software options for our Signal Analyzer MS269xA series, Universal Wireless Test Set MT8870A, and Signal Analyzer M2850A. By doing so, Anritsu’s portfolio includes single-instrument solutions that address 5G NR, as well as LTE, LTE-Advanced and other legacy technologies.”

Nichols, Keysight: “First, 4G is not going away—the requirements to ensure that 4G is working properly will be present for many years, so 4G measurement investments will be usable for some time to come. Secondly, some of what needs to be measured in 4G has very similar requirements to what must be done for 5G—especially in FR1. Therefore, with modest updates, 5G NR measurements for FR1 can be made using many 4G-capable test solutions. Third, there are clearly new requirements that drive architectural changes in test equipment—these must with either the move to FR2, or the move to much larger component carrier bandwidths in 5G compared to the 20MHz max in LTE—many of these mean investments in new platforms. Protecting investment here comes in multiple forms: Our new 5G capabilities must have legacy capability; and for products and solutions where that does not make sense, then we must ensure appropriate commercial terms—like with our technology refresh terms.”

Stasonis, Pickering: “This is where the idea of a modular framework comes into play. The modular infrastructure of our product family (software, communications, hardware) is common regardless of the frequency spectrum in which a customer is working. So as the demands on the switching technology evolve as 5G begins to be introduced into manufacturing, it is easy for a customer to adapt our products to meet these needs.”

AR RF/Microwave Instrumentation: “AR takes its global support and service very seriously. We want to provide the best possible solutions and for those solutions to last for years to come. AR has dedicated applications and service teams providing these solutions. This includes assisting customers through the buying process and for continued support for the life of their product.”

Thorpe and Helmick, Rohde & Schwarz: “R&S CMW500 customers can include 5G NR NSA and SA test options simply by adding a R&S CMX500 to the test setup. The R&S CMW500 is an industry standard for LTE testing.”

Luther, X-Microwave: “The analog RF is where we support users today in extending the life of their test-and-measurement investments. Any custom RF diagram can be put together like LEGOs and used in high quality production test applications, allowing a test engineer to fully customize their test set.”

Now on the market

Other than the aforementioned items these vendors have mentioned, what other products and solutions have recently been made available—or will be available soon—in the area of RF/microwave test and/or 5G test?

AR RF/Microwave Instrumentation: “Recently, AR has introduced the 350S1G6A and 500S1G6A amplifiers. These amplifiers both operate instantaneously from 0.7-6 GHz and deliver 350 Watts and 500 Watts of CW power, respectively. These new versions are ideal for testing in high-power mobile communications or may be used in situations requiring highly linear applications.”

Kerem Ok, product line manager, Communications Business Unit at Analog Devices: “ADI has a unique position in 5G mmW. First, we offer a complete ‘bits to RF’ signal chain hardware reference. Second, our 5G mmW product development offers bespoke features that support implementation of the essential algorithmic enhancements. Last, we are leveraging our existing knowledge from sub-6GHz and cable developments to position us at an advanced starting position on the development curve.”

Khan, Anritsu: “5G measurement software options are also available for our Signal Analyzer MS2850A to provide engineers with a cost-efficient and accurate solution to verify the RF Tx characteristics of next-generation 5G base stations and mobile devices. With the software installed, the MS2850A allows engineers to specify combinations of multiple component carriers up to 400 MHz and sub-carrier intervals.

Modular design with X-Microwave blocks around a semiconductor test socket.Modular design with X-Microwave blocks around a semiconductor test socket.Luther, X-Microwave: “A growing number of our customers are using X-MWblocks to build upconverters, down converters, and filter banks for use in their 6GHz, 18 GHx, and mmW RF test applications. Our modular design system allows a test engineer to supplement their instrument with high frequency amplifiers and other supporting components customized at-will.”

Infinite Electronics: “Products released within the past year include: Lab and field portable calibration kits; a completely new expanded line of advanced RF surge protectors; skew-matched cable pairs; an expanded line of custom low PIM coaxial cable assemblies; input-protected low noise amplifiers that provide noise figure levels as low as 0.8 dB; a new solderless vertical launch connectors with maximum operating frequency up to 50 GHz; and an innovative line of coaxial RF test probes and probe positioning hardware.”

Stasonis, Pickering: “We anticipate new product releases for the higher bandwidth in the second half of this year. We have upgraded our 40-8XX solid state switching to work at 8GHz in 2018. The 60-801 & 60-802 utilize small In 2018, Pickering Interfaces upgraded its 40-8XX solid state switching to work at 8GHz.In 2018, Pickering Interfaces upgraded its 40-8XX solid state switching to work at 8GHz.form/factor microwave muxes. The excellent repeatability of these devices operating at up to 40 GHz and achieving a very long life of more than 25 million cycles for testing up to 26.5 GHz. For test program development, all of our microwave mechanical switches feature LEDs to indicate the relays operating status.”

Thorpe and Helmick, Rohde & Schwarz: Some of the newest RF/microwave test applicable products at R&S include:

  • R&S CMX500—signaling tester for 5G NR FR1 and FR2. A single solution for all 5G Wireless device test applications.
  • R&S CMP200—single-box RF tester for 5G NR FR2 (24.25 GHz to 43.5 GHz), integrated VSA/VSG for R&D and production test
  • R&S ATS800B—compact antenna test range benchtop solution for 5G NR FR2 R&D

Nichols, Keysight: “Here are a few examples we are particularly proud of:

  • Simulation and design: ADS and SystemVue have multiple new capabilities aimed at the 5G market, including models of more high-frequency components as well as high-bandwidth and even phase-array design capabilities.
  • >100GHz coverage: We have signal analysis (UXA), network analysis (PNA-X), and now real-time time-domain analysis (UXR) in product platforms that have continuous coverage from the KHz region all the way to 110, and in some cases, 120 GHz.
  • Network emulation: Our 5G NR network emulation solutions cover SA and NSA, FR1 and FR2, and can cover legacy capability in 4G as well. These are the most popular solutions on the market today for UE test.
  • OTA: We started work on CATR technology and a few other companion OTA measurement capabilities back in 2015—with FR2, the OTA test capability becomes integral to the test equipment from the standpoint of calibration, coordination, and overall solution performance. These capabilities will be necessary not only for antenna and component-level testing, but also for system-level verification and conformance testing."

Initiatives & collaborations

What specific initiatives have vendors undertaken recently in conjunction with other companies, universities, or organizations, with respect to RF/Microwave Test, or 5G?

Yost and Chang, National Instruments: "NI has worked with commercial vendors like CommScope and Radisys to demonstrate how a multi-vendor 5G NR like can be created. A live demonstration of this collaboration was shown in April at the Brooklyn 5G Summit. At its annual showcase, NIWeek, NI announced the mmWave Vector Signal Transceiver (VST) to address the test challenges of 5G mmWave RFIC transceivers and power amplifiers, a major advancement for chipmakers working to accelerate 5G commercialization, as it expands previous offerings from the sub-6 GHz category to mmWave."

AR RF/Microwave Instrumentation: “AR maintains a seat on the TC77 working group tasked with development and maintenance of immunity test standards for the IEC. Additionally, AR continues working closely with customers from the various sectors such as wireless, R&D, automotive, aviation, consumer electronics, to ensure product offerings meet and exceed their current and future requirements.”

Nichols, Keysight: “Early in our 5G work, one of the top priorities was to get engaged with industry leaders to ensure research, development, and deployment was all being done with a close connection to the market. We now have over 50 collaborations (public announcements) around the world, with different types of entities, working on virtually every technology necessary to make 5G a reality. Some recent highlights with respect to RF/microwave include work with Qualcomm on industrial IoT, and work with Samsung on high-data-rate FR1 4X4 256 QAM devices.”

Luther, X-Microwave: “We’re supporting test instrument vendors supplementing their platform with custom signal conditioning solutions. Universities are also benefiting from the buzz around 5G with growing graduate student interest. Our platforms are being used for improving hands-on education and for transitioning from the research results from the lab to field-deployed systems."

 

For more information:
Analog Devices
Anritsu Company
AR RF/Microwave Instrumentation
Infinite Electronics
Keysight
National Instruments
Pickering Interfaces

Rohde & Schwarz
Total Temp Technologies
X-Microwave

More in RF/Microwave Test