Infusing GaN Power Amplifier Technology into Microwave System Design

Numerous components in all microwave systems have continuously evolved and are now being optimized for specific applications. Both military and commercial configurations can benefit from improvements in:

► Increased Sensitivity

► Reduced Size & Weight

► Higher Efficiency

► Reduced Cost

► System Power Efficiency

Improvements in these areas can spring from either the system designer or from breakthroughs at the component level.

Tracing their history back to Defense Advanced Research Project Agency (DARPA) investments in the mid 2000s, the latest generation of GaN-based semiconductors available to component manufacturers, points the way to many next-generation systems including radar, communication and unmanned aerial vehicles (UAVs).

With 5 to 10 times the power handling capability, a GaN device can handle twice the voltage and current of a comparable GaAs device. Likewise, with nearly 7 times the thermal conductivity of GaAs, GaN components can operate at a much higher temperature.

Capitalizing on these physical attributes CTT’s GaN-based amplifiers are designed to provide, for example, considerably more power than a GaAs or Silicon-based system while at the same time occupying a much smaller volume.

CTT engineers have developed a proprietary open architecture/common platform GaN-based power amplifier family, which relies on advanced coupler design and unique substrate material selection. The result is a selection of adaptable, modular amplifiers requiring only a single supply voltage.

These innovative new designs lend themselves to a variety of amplification functions in many current and future commercial and military systems. Additionally, whenever legacy systems are upgraded, whether to address new requirements or to benefit from improved technology, you can count on CTT’s thirty years of experience in microwave amplification and subsystem integration.

CTT offers not only form, fit, function of microwave amplifier replacements for many mature systems, but also incorporates leading-edge technology components.

Multipurpose, Flexible, Universal, and Scalable Designs

Only a few decades ago, military requirements and developments were a primary driving force of the microwave equipment market. With the emergence and explosion of the commercial communications market, military requirements now constitute a much smaller market share.

Since both commercial and military equipment share the same spectrum, they are bounded by physics and thereby share electrical characteristics. (DARPA-BAA-15-24, Shared Spectrum Access for Radar and Communications)

Fundamental to the differences is the commercial world’s established, well-maintained infrastructure. Military microwave, on the other hand, frequently operates without infrastructure in complex electromagnetic environments. This includes hostile temperatures, shock and vibration.

These tactical issues are different enough from commercial environments to warrant additional design and manufacturing considerations. The key issues being:

• • Temperature operating ranges

• • Tolerance to moisture

• • Tolerance to vibration

• • Tolerance to high altitude environments

• • Tolerance to G-forces

• • Cycle life

Commercially derived designs, technology and processes, commonly referred to as Commercial Off-the-Shelf (COTS), can be successfully applied to these military systems requirements, potentially increasing overall system performance. The advantages of this approach are readily understood. Commercial electronic designs are often more advanced than what is currently available within the military sector.

Taking these factors into consideration, CTT’s latest evolution of GaN and GaAs microwave amplifier designs are truly “Dual Use.” The difference between commercial and military applications is being addressed by insertion of military grade components into basic design layouts, subject to the appropriate Mil-Standard screening procedures.

Moreover, a single CTT amplifier design, due to it’s wideband performance envelope, is often suitable for diverse applications (i.e.: from radar, to instrumentation, to commercial communications). CTT’s design philosophy offers the customer military or commercial significant benefits by:

• • Mitigating risk with proven technology

• • Reducing time-to-market

• • Reducing overall system cost

CTT GaN Power Amplifiers

CTT’s newest GaN power amplifiers are finding applications in many of the next generation of high-performance Synthetic Aperture Radar (SAR) on both commercial and military UAVs. With SAR transmit power requirements of less than 100 watts at X-band, and UAV payload maximums of less than 50 pounds, CTT’s new GaN power amplifiers – with 30% operating efficiencies – offer cost-effective performance solutions as final transmission elements.

With system power consumption as an increasingly important design criteria CTT offers TTL-controlled main bias shut-off circuitry matched to the system’s pulse operation. With the amplifier drawing much less power between pulses, both total power consumption and temperature rise is reduced.

As an example, most commercial and military pulse radars operate at a duty cycle of 10% or less. As such, CTT’s GaN power amplifiers are an attractive solution. Using a TTL control, by turning off the FETs (drain) the amplifier only consumes 100 to 200 mA for the logic and bias circuit. When the TTL is turned on, the unit will operate after a short rise time. During this “on time” the amplifier’s power consumption is identical to that in CW operation. Thus, when the duty cycle is 10% or less, the unit will consume much less power. Therefore, the amplifier’s heat sink and power supply can be significantly smaller.

Engineered specifically to meet the stringent requirements imposed by many modern system designs, CTT’s family of GaN power amplifiers, perform a wide range of functions making them ideal for applications in cutting-edge multi-function systems. Whether the application is narrowband, wideband or ultra-wideband, operating in pulsed or CW mode, CTT’s GaN power amplifiers are an especially attractive choice for new multi-functioned systems that effectively conserve weight, space and power consumption.

CTT’s amplifiers are designed for commercial, industrial and military applications. For military applications power amplifiers are manufactured to meet the requirements of MIL-STD-883, Methods 2010 and 2017, with soldering compliant to J-STD-001. These procedures also make the amplifiers excellent choices for applications requiring MIL-E-5400.