MMIC design demonstrates up to 13.1W of output power over 1 to 8GHz bandwidth
Qorvo, a developer of RF systems and solutions for wireless and broadband communications, has recently used NI’s AWR Design Environment to meet the requirements for a GaN-based power amplifier with high output power, wide bandwidth, and high efficiency.
Many modern microwave electronic systems specify amplifiers with high output power, wide bandwidth, and high efficiency. Until recently, most wideband high-power amplifier (PA) solutions have relied on vacuum electronics-based technologies. Recent work, however, shows steady progress in realising high-power, high-frequency, wideband amplifiers using GaN monolithic microwave integrated circuit (MMIC) technology that operates from near DC up to 7 GHz.
The Qorvo team used NI AWR Design Environment to develop a 1 to 8 GHz PA MMIC fabricated with a 0.15µm GaN process technology. The process featured a 100 μm thick SiC substrate and compact transistor layouts with individual source grounding vias (ISVs). The design used a non-uniform distributed PA (NDPA) topology with a novel trifilar connected output transformer.
Design goals for PA MMIC were: 1 to 8 GHz bandwidth, > 25 dB small signal gain, 10 W saturated output power, and power-added efficiency (PAE) exceeding 30 percent. A small-signal gain goal in excess of 25 dB required at least two amplification stages.
The resultant two-stage amplifier demonstrated 9.3 to 13.1W of output power over a 1 to 8GHz bandwidth with greater than 29 percent associated PAE. Theoretically transformation ratios up to 2.25:1 are possible depending on the location of the output tap. Due to physical limitations regarding the location of the low impedance side tap, the microstrip implementation produced a ratio closer to 2:1.
According to the company, the performance of the PA compared favourably to recently published GaN MMIC PA benchmark results for bandwidth, gain, die size, and efficiency. It says that the success of this project was due to the powerful circuit design capabilities of Microwave Office software combined with integrated AXIEM 3D planar electromagnetic simulation.