RF/Microwave Technologies Advance For Military Systems

June 13, 2008
From the device level through signal sources and integrated assemblies, suppliers of RF/microwave components continue to contribute to advances in military electronic systems.

Military electronics systems generally leverage the latest technologies in order to achieve performance or even tactical advantages. Although systems, such as radar and electronicwarfare (EW) platforms, are comprehensive collections of analog, digital, and RF circuits and devices, it is often the technology in a part as small as a transistor that can have an enormous impact on the overall performance of a military electronics system.

For example, earlier this year Microsemi Corp. (www.microsemi.com) released the model TAN500 power transistor for TACAN avionics transmitters. The transistor delivers 500 W output power from 960 to 1215 MHz when driven with 70-W, 10-microsecond pulses. The Class C bipolar transistor is designed for use at +50 VDC. The transistor die, with at least 9-dB power gain and collector efficiency of at least 40 percent, features gold metallization and integral emitter ballast resistors for maximum reliability.

According to Russell Crecraft, general manager, Power Products Group for Microsemi (Bend, OR), "Customers are continually looking for higher-power transistors for TACAN applications. The challenge for the device supplier is to provide such a device that can cover the broad bandwidth and heavy pulsing requirements for TACAN transmitters. Microsemi has met that challenge with the TAN500. The customer can now greatly simplify the design of KW transmitters."

Likewise, transistor supplier HVVi Semiconductors, Inc. (www.hvvi.com) earlier this year announced a major advance in silicon RF transistor design that will also benefit pulsed military RF electronics systems, such as Mode S and TACAN transmitters. The company's latest transistors are based on the firm's novel High Frequency, High Voltage Vertical Field Effect Transistor (HVVFET) technology, using an architecture that promises wider bandwidth, higher voltage, and higher power levels for radar and avionics applications than traditional silicon bipolar and LDMOS device technologies.

The patent-pending technology is the basis for three new transistor products targeted at high power, pulsed RF applications at L-band frequencies, such as IFF, TCAS, TACAN, and Mode-S, transmitters. All three transistors are designed to operate at +48 VDC. Model PVV1011-300 delivers more than 300 W pulsed output power from 1030 to 1090 MHz while providing 15 dB of gain and 48 percent typical efficiency with 50-microsecond pulses at a pulse period of 1 ms. The device is specified to withstand a 20:1 VSWR at all phase angles under full-rated output power.

Models PVV1214-25 and PVV1214- 100 are enhancement-mode RF transistors for L-band pulsed radar applications from 1.2 to 1.4 GHz. Designed for use at +48 VDC, the devices deliver 25 W and 100 W output power, respectively. With 200-microsecond pulses and a pulse duty cycle of 10 percent, model PV1214-25 provides 17.5 dB gain and model PV1214-100 offers 19.5 dB typical gain. Both transistors are capable of withstanding an output load mismatch corresponding to a 20:1 VSWR at rated output power and nominal operating voltage across the entire frequency band of operation. The 25-W driver transistor is supplied in a surface-mount package while the higherpower devices are housed in standard flange-mount packages (Fig. 1).

As Wil Salhuana, president and CEO of HVVi noted: "While currently used silicon RF transistor technologies such as bipolar and LDMOS have served radar and avionics designers well, they have hit a ceiling in terms of performance. By creating the first high-frequency, highvoltage vertical field effect transistor, we have redefined the performance capabilities of the discrete silicon power transistor and opened the door to a vast array of new applications."

Earlier this month, Freescale Semiconductor (www.freescale.com) announced the first 50-V silicon LDMOS transistors designed for L-band avionics applications. The 50-V capability greatly simplifies integration into aircraft power-supply systems. The new product line includes two transistors designed to work together in an avionics or radar transmitter circuit: the model MRF6V14300H final stage device and the model MRF6V10010N driver device. The MRF6V14300H delivers 330 W pulsed output power from 1200 to 1400 MHz with extremely high efficiency and gain, and excellent thermal characteristics for good long-term reliability. The model MRF6V14300 device achieves 17-dB gain with 60-percent drain efficiency when amplifying a 300-microsecond pulse at 12-percent duty cycle to its rated 330-W output power. The driver device, model MRF6V10010N, provides 8 W peak output power at 1400 MHz with a 300-microsecond, 12-percent-duty-cycle signal, with 22-dB gain and 60-percent drain efficiency. The new devices are fabricated with Freescale's six-generation very-high-voltage (VHV6) 50-V LDMOS technology. Both devices incorporate electrostaticdischarge (ESD) protection to guard against improper handling. The highpower model MRF6V14300H is housed in a RoHS-compliant air-cavity ceramic package while the MRF6V10010N driver is supplied in an over-molded plastic package.

In terms of broadband gain, few devices can match the TGA4830 chip amplifier from TriQuint Semiconductor (www.triquint.com). Measuring just 1.79 x 1.00 x 0.11 mm, the amplifier features DC-coupled input and output ports and total coverage of DC to 45 GHz. It provides 13 dB gain at 20 GHz and an automatic gain control (AGC) range of better than 20 dB. Based on 0.15-micron pseudomorphic-high-electron-mobilitytransistor (PHEMT) technology, the amplifier chip is well suited for EW systems as well as test and measurement applications. It delivers +11.5 dBm output power at 1-dB compression with input and output return los of 15 dB. The broadband amplifier draws 50 mA from a +5-VDC supply.

TriQuint recently announced a large order of gallium nitride (GaN) wafers from semiconductor wafer supplier IQE plc (www.iqep.com). The GaN wafers are intended to to support ramping up new commercial and military products at TriQuint. According to TriQuint Research and Development manager, Anthony Balistreri, "IQE's established track record in providing TriQuint with reliable, high-quality products was a key factor in selecting them to produce and deliver a range of advanced GaN epitaxial materials. We've developed a close working relationship with IQE throughout the development phase of our GaN program." TriQuint's recent order for GaN epitaxial high-electronmobility- transistor (HEMT) wafers from IQE's New Jersey facility will be used in ongoing military and commercial R&D efforts while supporting TriQuint's new products in 2008.

For generating system-level signals, Micro Lambda Wireless (www.microlambdawireless.com) offers its MLOB and MLOS series of wideband YIG-tuned oscillators with integrated militarygrade digital drivers for test and system applications from 700 MHz to 20 GHz. These low-phase-noise oscillators can be supplied with 12-b digital driver circuitry to simplify integration into military electronic systems. The oscillators and drivers are rated for operating temperatures from -40 to +85C.

For timing applications, the Firefly from Jackson Labs (www.jackson-labs.com) represents true miniaturization in a Global Positioning System Disciplined Oscillator (GPSDO). It measures a mere 1.25 cubic inches even though it is based on oven-controlled-crystaloscillator (OCXO) technology. The GPSDO delivers Stratum-1 long-term frequency-stability performance of better than 10 parts per trillion, or 1 x 10 -11 averaged over a 24-hour time period when locked to a GPS signal. It provides an OCXO-driven 1 pulse per second (PPS) output signal that is phasesynchronized to better than 100-ns root mean square (RMS) to Universal Time Code (UTC) and a synchronized lownoise 10-MHz sinewave output signal at +12-dBm level.

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To keep signals connected, M/ACOM (www.macom.com), a Tyco Electronics company, recently announced its FE series of ruggedized mast cables for severe environments and handling. The smallest-diameter cables in the family, the FE25 cable, has an outside diameter of 0.25 in. The cable is usable over a theoretical bandwidth of DC to 23.5 GHz (which will ultimately be limited by the terminating connectors. The FE25 cables are designed to handle as much as 450 W power at 2 GHz and more than 175 W of power at 9.9 GHz. The insertion loss is 8.803 dB/100 ft of cable at 1 GHz and about 34 dB/100 ft of cable at 10 GHz. The nominal velocity of propagation is 76 percent, with nominal delay of 1.337 ns/ft. The FE25 cable exhibits nominal capacitance of 26.8 pF/ft.

The FE series cables are available with outside diameters ranging from 0.25 to 1.40 in.; all cables are rated for operation from -55 to +125C. The largest-diameter cables in the FE series, the FE140 cable, has an outside diameter of 1.4 in. and is usable over a bandwidth of DC to 3 GHz. This robust cable is rated for power-handling capability of about 17 kW at 1.65 GHz. The FE series ruggedized mast cables (see figure) feature an integral helically wrapped, stainless-steel spring to provide maximum durability and strength plus an extruded polyurethane outer jacket to protect it from abrasions and ultraviolet (UV) radiation damage.

For boosting the levels of signals in military electronics systems, Comtech PST (www.comtechpst.com) recently announced its model BHED2739 highpower amplifier system for applications from 20 MHz to 3 GHz. The system delivers 1 kW CW power from 20 to 512 MHz, 500 W CW power to 1 GHz, and at least 200 W CW output power from 1 to 3 GHz. It can switch between one frequency and another anywhere in its range within 50 microseconds, including the time required to switch between its extensive filtering networks and as many as four antennas optimized for the appropriate frequency band. The system incorporates comprehensive self-protection capability and extensive harmonic filtering.

The model BHED2739 high-power amplifier system can handle a wide range of operating conditions, from low VSWR to an infinite VSWR load mismatch, and can operate comfortably with even complex loads presented by log-periodic antennas. The high-linearity Class AB design of the amplifier system allows it to work with a wide range of modulated signals, including amplitude modulation (AM), frequency modulation (FM), pulse modulation (PM), and single-sideband (SSB) signals. The system features harmonic suppression of -50 dBc and spurious suppression of -60 dBc. The high-power amplifier system operates from a 230 or 400 VAC supply, meets MIL-STD-810F shock and vibration requirements, and can be remotely controlled by means of Ethernet, RS-422, or RS-232 connection.

At the system level, Boeing (www.boeing.com) recently achieved a major milestone in its development of the Airborne Laser (ABL) missile defense program. Based on high-power chemical laser technology, the ABL system is being developed as a means of shooting down ballistic missiles. The first laser activation testing was conducted on the ground earlier this year at Edwards Air Force Base in California, with a shootdown demonstration of the technology against a ballistic missile planned for 2009. The ABL aircraft consists of a modified Boeing 747-400F whose back half holds the high-energy laser, designed and built by Northrop Grumman. The aircraft's front half contains the beam control/fire control system, developed by Lockheed Martin, and the battle management system, provided by Boeing.

In a different technology area, Boeing successfully flew its A160T Hummingbird unmanned rotorcraft for 18.7 hours this past May 14 and 15, posting an unofficial world's endurance record for an unmanned aerial vehicle (UAV) weighing between 1102 and 5511 pounds (between 500 and 2500 kg). As Jim Martin, Boeing Advanced Systems A160T program manager, noted: "We didn't set out to establish a world record, but it was a great accomplishment. This 18-hour endurance flight is the culmination of thousands of hours of systems, ground and flight testing. The aircraft performed flawlessly, flying un-refueled longer than any other current unmanned rotorcraft. Our customers are excited about this important flight, the needs the A160T fills and the many options it gives warfighters." Testing was performed at the US Army's Yuma Proving Ground in southwest Arizona. The UAV carried a 300-lb payload at altitudes to 15,000 ft. The aircraft landed with more than 90 minutes of fuel in reserve.

In communications systems, Raytheon Co. (www.raytheon.com) received an $11.74 million contract from the US Army Communications-Electronics Command for delivery of 205 Global Broadcast Service (GBS) transportable ground receive suites and associated spares. The GBS suites allow mobile Army users at the edge of a battlefield to receive broadband data and video signals and process them for use by military decision makers and frontline troops.

In its newest research facility in Salt Lake City, UT, Raytheon is also at work on developing a robotic suit for nextgeneration US Army soldiers. Known as the Exoskeleton, the suit is a robotic "garment" that amplifies the wearer's strength, endurance, and agility in the manner of the popular movie "Iron Man." The Exoskeleton is constructed from a combination of sensors, actuators, and controllers, and allows the wearer to easily carry another person on their back. The Exoskeleton project, headed by Dr. Stephen Jacobsen, has been in progress since 2000, with the vision of a man working not only alongside robots but also inside one.

On a smaller scale, Raytheon's Integrated Design Systems (IDS) is also involved in DARPA's Compound Semiconductor Materials on Silicon (COSMOS) program to demonstrate that affordable, high-performance circuits for military applications can be produced by growing semiconductor compounds directly on silicon. According to Mark Russell, vice president of Engineering at Raytheon Integrated Defense Systems (IDS), "Our team's process of directly growing a semiconductor compound on a uniquely engineered silicon substrate provides a technical approach that is creating a new class of integrated circuits that will be more affordable for our Defense Department customers."

Dr. Tom Kazior, program manager at Raytheon IDS, added: "Selective placement of semiconductor compounds on silicon is an important achievement because it proves that optimal circuit performance can be produced through a heterogeneous, high-yield, monolithic integration process." Raytheon IDS is teamed with a number of other companies on the COSMOS project, including Raytheon Systems Ltd. (Glenrothes, Scotland); Teledyne Scientific Imaging Co. (Thousand Oaks, CA); Massachusetts Institute of Technology (MIT, Cambridge, MA); Paradigm Research LLC (Windham, NH); IQE (Bethlehem, PA); Soitec (Grenoble, France); and Silicon Valley Technology Center (San Jose, CA).

Among its many programs, Raytheon is also involved in the US Army's (www.army.mil) Common Sensor Payload (CPS) program. The program is an attempt to create synergies in technologies and capabilities from the use of common sensors across multiple manned and unmanned systems. As part of developing solutions for the CPS program, Raytheon is able to leverage experience on a number of different electro-optical/infrared (EO/ IR) sensor-based systems including the AN/DAS-2 on the US Army's Extended Range Multi-Purpose Unmanned Aerial System; the AN/AAS-52 and AN/DAS-1 on the US Air Force Predator and Reaper Unmanned Aerial Systems, respectively; as well as the AN/AAS-44(C) system on US Navy MH-60R/S helicopters and the AN/ZSQ-2 system on USSOCOM helicopters.

Also in support of military communications, Northrop Grumman Corp. (www.northropgrumman.com) was recently awarded the first phase of a four-phase advanced research contract by DARPA to design and build a cluster of wirelessly interconnected free-flying spacecraft. The Future, Flexible, Fast, Fractionated, Free-Flying, Spacecraft united by Information Exchange (F6) program is a 12-month study of ways to break up a typical monolithic satellite into distributed modules. In Phase 1, Northrop Grumman will develop a satellite-to-satellite wireless network, a distributed command and control system, and network protocols. An actual flight demonstration composed of multiple satellites will be developed in subsequent phases.

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This DARPA program hopes to explore the viability of a cluster of wirelessly connected spacecraft modules in place of a traditional satellite. In this distributed approach, each module contributes a unique capability such as command and data handling, guidance and navigation, and payload functions. At the same time, virtual and distributed satellite components do not interfere with each other, do not have to be developed on the same schedule and can be replaced more cost effectively. Lisa Hill, Northrop Grumman F6 program manager, noted: "We are pleased to be selected to work on such an exciting program that lays the foundation for the next generation of space systems.

The fractionated approach ushers in a new paradigm of architecting space systems, providing significant value to our existing customers and enabling new missions and capabilities. Additionally, the F6 concept offers a level of flexibility and robustness unprecedented in space."

In some cases, military customers reach for the same suppliers that have been reliable for their civilian counterparts. For example, the QuicLINK system developed by Ericsson (www.ericsson.com) is a portable network designed for tactical broadband communications and based on third-generation (3G) WCDMA technology. The QuicLINK technology is available in a man-portable format or in a vehicleready configuration. The man-portable version measures 35 x 22.83 x 22.05 in. and weighs 11.85 lbs., while the vehicle system is supplied in a standard 19-in. rack-mount enclosure weighing 86.24 lbs. The QuicLINK system provides public telecommunications-grade voice, video, and data communications with ease of setup in the field.

The secure communications network is compatible with any standard WCDMA handset or personal-computer (PC) communications card. The QuicLINK technology, which is based on commercial-off-the-shelf (COTS) products, provides full WCDMA network functionality as part of an integrated Radio Access Network (RAN) and mobile Core Network (CN). The spread-spectrum WCDMA technology provides high resistance against electronic warfare disruptive efforts and is capable of transporting encrypted communications traffic for additional levels of secure communications. QuicLINK units communicate by means of IP Wide Area Network (WAN). The system is capable of connecting with the Public Switched Telephone Network (PTSN) as well as with a Private Automatic Branch Exchange (PABX). The network features Internet Protocol (IP) connectivity, with mobile stand-alone operation with the capability to connect to legacy communications networks.

About the Author

Jack Browne | Technical Contributor

Jack Browne, Technical Contributor, has worked in technical publishing for over 30 years. He managed the content and production of three technical journals while at the American Institute of Physics, including Medical Physics and the Journal of Vacuum Science & Technology. He has been a Publisher and Editor for Penton Media, started the firm’s Wireless Symposium & Exhibition trade show in 1993, and currently serves as Technical Contributor for that company's Microwaves & RF magazine. Browne, who holds a BS in Mathematics from City College of New York and BA degrees in English and Philosophy from Fordham University, is a member of the IEEE.

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