GaN based Driver and Power Amplifier MMICs for X-Band Transceiver Modules

This work presents the design and implementation of two power amplifiers along with a driver amplifier based on our in-house microstrip 0.25 μm GaN on SiC technology. Details of the fabrication technology, typical transistor performance, MMIC design procedure, and measurement results of the fabricated chips are provided. The presented amplifier chain is planned to be used in an X-band transceiver module. The compact size driver amplifier demonstrates at least 25 dB gain and has a minimum of 23 dBm output power at 1 dB gain compression, which is sufficient to drive the power amplifier MMICs comfortably. For the power amplifiers, two design approaches are taken. The first design provides a maximum output power of 20 W with 27 dB power gain at the center frequency of 10 GHz, while the second one is optimized for flatter small-signal and large-signal responses. The second power amplifier achieves at least 17.6 W across the desired band with a minimum of 33% power-added efficiency and also provides 35.2 dB small-signal gain with a considerably low gain ripple of 0.8 dB. The complete amplifier chain is expected to demonstrate a high gain and high output power density with low ripple at 85°C operating temperature.

I. Introduction

Gallium nitride (GaN) transistors and monolithic microwave integrated circuits (MMIC) are widely used in modern military and civilian radars. The technology is now well known and has established decent results which encourage its use in the future systems. High breakdown voltage, high sheet charge, and high saturated drift velocity of the material enable GaN transistors to outperform other technologies in achieving high output power capability [1]. Recent studies have obtained very high output power densities at -band using SiC as the substrate material benefiting from its excellent thermal properties [2], [3]. Promising results at -band are reported in transceiver modules with GaN based amplifier chains [4]–[7].