NF: Some people in the microwave industry are starting to predict that gallium-nitride (GaN) devices could replace traveling-wave-tube amplifiers (TWTAs) in a few applications. Do you think there is any merit to those claims?
FO: TWTAs continue to deliver the highest levels of RF power over the widest bandwidth at microwave frequencies. As evidenced by our recent (and largest) contract with the US Navy, the demand for TWTAs remains high. This is especially true as we continue to push wider bandwidths and higher frequency limits. Improvements in tube reliability and life cycle (up to 100,000 hours) also have helped to keep the market for traveling-wave tubes (TWTs) strong and steady. While GaN devices have inevitably secured a role in a select number of future electronic-warfare (EW) operations, many modern mission-critical applications require the combination of high power and high frequency range that is only provided by TWTAs.
NF: Cutting-edge military applications continue to drive TWTA usage and development. Can you provide a glimpse of “state-of-the-art” applications for today’s TWTAs?
FO: As electronic countermeasures (ECM), radar, communications, and other EW systems increase in sophistication, design engineers must create secure, reliable, and accurate systems that are invulnerable to modern threats. One of the most successful examples is the MQ-9 Reaper (originally the Predator B) unmanned aerial vehicle (UAV). Operated remotely from thousands of miles away, this drone can fly for 30+ hours at altitudes of more than 50,000 ft. The remote pilot’s “eyes” come in the form of a high-resolution, Lynx multi-mode radar that operates in synthetic-aperture-radar (SAR) and ground-moving-target-indicator (GMTI) modes. Here, image accuracy is directly connected to the performance, reliability, and operational capacity of high-power TWTAs.
NF: What military applications are driving very-high-power product development? Can you provide an example of the devices being created and the performance levels that they are reaching?
FO: Very-high-power product development is driven by next-generation applications, such as 
radar, EW, ECM, and airborne data links. As these applications continue to change the landscape of the modern battlefield, it’s critical to achieve the following design goals: improve overall amplifier performance, increase power output, enable frequency agility, increase efficiency, and reduce size and weight. At the Association of Old Crows (AOC) Conference in Phoenix, AZ this month (Sept. 23-26; www.crows.org/conventions/conventions.html), we’re debuting a suite of TWTAs that use two wideband, period-permanent-magnet (PPM)-focused, phase-matched TWTs in a single amplifier. In doing so, they can amplify continuous-wave (CW), amplitude-modulation (AM), frequency-modulation (FM), or pulse-modulated signals. Operating in the 2-to-18-GHz range with output reaching 10 kW peak at 6% duty cycle (depending on model number), these new devices are designed and manufactured specifically for demanding military applications. With only one RF input and one RF output (similar to single TWT configurations), the new TWTAs also are easy to operate.
NF: How much of your current business is focused on the UAV market? How do you expect that market to grow over the next few years?
FO: Because the radar systems and data links on-board UAVs are essential to today’s military operations, a significant portion of dB Control’s business is focused on this market. These high-performance aircraft are in demand by both government and commercial entities because they enable operating personnel to stay out of harm’s way. It is one of the few areas in the military budget that is still growing despite expected budget cuts.
NF: How have UAVs steered your new-product development?
FO: The Department of Defense (DoD) will always support critical technology that anticipates future enemy threats and keeps our military personnel safe. Now, there also is an increase in commercial applications, such as border patrol, shipping-sea-lanes patrol, natural disasters, and flood and wildfire detection. Continued advancements in UAVs will further propel new product development. In addition to TWTAs, dB Control manufactures microwave power modules (MPMs) that have a mini-booster TWT and power supply in a compact package. Our products have been used on a large number of unmanned airborne platforms including the RQ-4 Global Hawk and MQ-4C Broad Area Maritime Surveillance.
NF: Which UAV capabilities have been especially difficult to support?
FO: In addition to bandwidth and power requirements, the military has stringent specifications for product size and weight. To meet these needs, dB Control developed proprietary transformer fabrication, encapsulation, and high-voltage potting techniques, which enable components to be compactly held within the final product. Our MPMs in particular combine TWT and solid-state technology to create a compact, high-power amplifier that meets tactical needs for bandwidth, power output, and efficiency.
NF: Drones have been ordered to begin flying in US airspace by 2015. At that point, do you expect your UAV business to reach a plateau or continue to grow?
FO: We expect that our UAV business will continue to grow—especially considering the potential for valuable non-military applications. UAVs like the RQ-4 Global Hawk are in demand because of their ability to remotely cruise for more than 30 hours at altitudes above 65,000 ft. Civilians are apprehensive about drones operating in the same space used by commercial and passenger planes. Yet many don’t realize that these aircraft have been flying in the US for years—detecting wildfires, monitoring pollution, and performing search-and-rescue missions.
NF: Have you seen any trends in improved reliability in TWTs over the last 10 years? Do you feel that the sources for TWTs are reliable for the next 10 years?
FO: TWT technology has improved exponentially in the last decade in terms of power, bandwidth, frequency, and reliability. While some of our industry colleagues doubted tubes’ staying power, many are beginning to realize what our customers already know: TWTs are incredibly reliable. They boast meantime-between-failure (MTBF) rates of more than 10 years. Plus, we use TWTs from several established manufacturers, such as Teledyne, CPI, e2v, and Thales. We are certain that we will have reliable TWT sources for decades to come.
NF: How have advances in thermal-management materials, including PCBs, helped you achieve your performance goals?
FO: dB Control continues to analyze the latest thermal-management materials in order to develop the best possible thermal interface for our products. We regularly conduct a detailed thermal analysis on all development programs to achieve high thermal dissipation, as our products often push the power limits within a small area.
NF: With military budgets being cut, many military-focused companies are worried about retaining their profits over the next few years. How does dB Control plan to weather the storm?
FO: DoD budgets are certainly top of mind. However, the microwave/RF industry remains profitable. In fact, the DoD’s Unmanned Systems Integrated Roadmap (FY 2011-2036)1 highlights the value of unmanned systems in terms of persistence, versatility, and reduced risk to human life. The executive summary states: “DoD will partner with industry to continue to invest in unmanned systems technologies while providing incentives for industry to implement cost-saving measures and rewarding industry members that routinely demonstrate exemplary performance.” As dB Control provides the underlying technology on-board several next-generation military platforms, including UAVs, we feel that we’ll continue to be a reliable source of TWTAs and MPMs.
1. Department of Defense Unmanned Systems Integrated Roadmap (FY 2011-2036): http://www.acq.osd.mil/sts/docs/Unmanned%20Systems%20Integrated%20Roadmap%20FY2011-2036.pdf.