Figure 1: A large number of antennae can be reduced.

Future trends for military radar require multifunction systems that combine radar, communications, and electronic warfare. This higher level of functional integration improves battlefield performance through heightened awareness, improved responsiveness, and mission execution. Integrated Top Side (INTOP) is one such example where the Office of Naval Research (ONR) is leading the charge in combining a “forest of antenna masts” into a single, multi-function Active Electronically Scanned Array System (AESA) aperture. Figure 1 shows the large number of antenna arrays and complexity of shipborne radar that can be dramatically simplified by the INTOP program.

For commercial radar applications, multiple frequencies are being combined into a single antenna system to enable multi-role capabilities such as air traffic control, weather radar, and communications all in one. Multi-mission Phased Array Radar (MPAR) is an example of a commercial program where a highly integrated AESA approach will provide weather and aircraft surveillance for public weather services, air traffic control, and homeland defense. MPAR will replace up to eight different radar systems that currently employ a traditional mechanical antenna system. Multi-function radar systems require AESA antennas that provide significant performance and capability improvements; however, the vast number of elements in the array requires a compact power RF solution that also offers significant improvements in size, weight, and power (SWaP).

The Importance of GaN

Achieving the required power performance is critical to enable greater capability and flexibility in new radar systems. Gallium nitride (GaN) power devices, with significantly higher breakdown voltage and thermal performance compared to Si Bipolar and LDMOS, create a new paradigm in power performance. With improved efficiency, power density, frequency bandwidth, and thermal performance, dramatic benefits can be achieved when using GaN. Some of the many benefits are:

  • Increased power density leads to greater power levels in smaller size.
  • Higher efficiency improves thermal performance and reduces power supply demand.
  • Higher voltage operation allows for wide-band impedance matching.
  • Higher voltage operation reduces the size requirements of energy storage capacitors, while also reducing current handling within the power supply system.
  • Improved thermal performance leads to greater flexibility in pulse and CW operational modes.
  • High breakdown voltage significantly improves ruggedness under load mismatch conditions, and allows for greater flexibility in signal waveforms for multi-function roles.

GaN semiconductor technology sets a new standard in power performance that enables new multi-function radar systems. However, the implementation of GaN into next-generation radar systems requires a revolutionary approach to packaging and assembly.

GaN in Plastic Packaging

Figure 2: Ultra-small 3x6-mm DFN package.

GaN in plastic packaged power transistors enable high-performance civilian and military radar and communications systems. GaN in plastic power transistor products can be mounted on PCBs via ground/thermal arrays. Internal stress buffers allow the devices to be reliably operated at up to 200 °C channel temperature. These transistors are capable of operating at frequencies up to at least 3.5 GHz.

Scaling to high pulse power levels of 100W, GaN in plastic transistors aim to defy the power, size, and weight limitations of ceramic-packaged offerings to enable a new generation of high-performance, ultra-compact military and civilian radar systems

Packaged in as small as 3 × 6-mm dual-flat no leads (DFN) and standard small outline transistor packages, GaN in plastic transistors can be tweaked to perform at 50V drain bias, resulting in outstanding power density and performance, higher efficiency, and smaller impedance matching circuits due to improved device parasitics. The high-voltage operation also benefits overall system design with smaller energy storage capacitors and lower current draw.

GaN in plastic-based power transistors are also extremely lightweight compared to the existing ceramic-packaged offerings currently available. Measured in aggregate across the hundreds of power amplifiers within a typical modern radar system, this can reduce overall system weight considerably. The resulting weight reduction ensures greater ease of movement for mobile radar systems.

High-performing and innovative GaN in space-saving plastic enables radar system designers to take full advantage of GaN technology and achieve new levels of power density while reducing system size and weight significantly. Utilizing sophisticated packaging and thermal management techniques to maximize design efficiency and component reliability enables designers to overcome challenging development hurdles and pioneer a new generation of high-performance, rugged radar systems that transcend the capabilities of systems that are built around conventional GaN in ceramic packages.

SMT GaN Modules

Figure 3: SMT Modules (left) as compared to a traditional power pallet (right).

The GaN in plastic approach also allows for ultra-small, fully matched, integrated module solutions. The next evolutionary step is to develop high-gain power modules based upon the GaN in plastic power transistors for the L- and S-Band radar markets. The modules are fully matched with two stages of high gain, and are realized using Surface Mount Technology (SMT) assembly on a very small RF board with 14 × 24-mm dimensions.

An example of the SMT GaN power module is shown in Figure 3. The module implements very compact lumped element matching to achieve full 50- Ohm matching across the band. The GaN power transistors are assembled using standard reflow techniques, and the module can be easily integrated into a radar system front end.

The ability to offer a full SMT solution using GaN combines the best of advanced military power technologies and high-volume commercial manufacturing expertise. With this combination it is possible to break through the current boundaries of SWaP, and realize a new level of performance and capability in future radar systems.

Looking Ahead: GaN in Radar and Communication Markets

Improving power performance while reducing the size, weight, and cost of power solutions will allow next-generation radar systems to achieve new levels of multi-function performance. The changing landscape brings with it the drive to achieve open architecture and modular systems. These will require plug-and-play type T/R modules that can be easily integrated into AESA radar and multi-function systems. GaN is a key component to meet the challenge for these multi-function systems and open architecture radar development.

The inherent high power and excellent efficiency properties of GaN lend itself towards multi-function roles due to the flexibility and capability of the power technology. Through GaN in plastic technology, which combines the best of commercial and military technologies, a new blueprint is being created for SWaP performance. Surface mount manufacturing, along with small-size integrated module solutions that can be combined with additional RF components to form complete T/R modules in AESA radar systems, is leading to a true modular RF solution for next-generation radar systems.

This article was written by Paul Beasly of M/A-COM Technology Solutions (MACOM), Lowell, MA. For more information, Click Here