Equipment designers often face power-level requirements that far exceed what is achievable from a single solid-state device. While laterally diffused metal-oxide semiconductor (LDMOS) devices offer ever-higher power levels, gallium-nitride (GaN) technology takes it one step further: GaN brings higher power densities and efficiencies to the designer’s toolbox, making it possible to achieve even more power in smaller packages while reducing the overall size of the final solution.
Paralleling two or more RF power devices to increase power levels is still routinely done in the industry. However, a better way to scale power when combining multiple devices is to push the output power of single-ended transistors to significantly higher levels. This simplifies the bias needs and distribution, reduces size and weight, and enables additional system benefits previously contained in two rack-and-stack amplifier boxes. This article reports on the attributes and benefits of using these very-high-power transistors in the design and application of next-generation L-band systems.
Invigorating L-Band with GaN
As manufacturers address re-engineering existing L-band systems, GaN offers key benefits that lead to new capabilities. Bipolar transistors used in traditional avionics and radar capabilities have already been replaced by both LDMOS and GaN transistors to more than double power while maintaining power-supply dissipation levels. The new transistors’ greater levels of gain and efficiency are the main reasons behind the surge in power. Numerous suppliers already offer 500-, 600-, and 700-W transistors to make such a cascade possible. Figure 1 shows a conceptual block diagram of a typical 3.2-kW amplifier.