The DARPA FLARE Program: Recent Advances in Ultra High Linearity RF Amplifiers

The DARPA Feedback Linearized Amplifier for RF Electronics (FLARE) Program has demonstrated the world´s first microwave operational amplifier with record linearity through the use of strong negative feedback made possible by the large available gain-bandwidth product in state-of-the-art Indium Phosphide (InP) transistor technologies. The output third-order intercept point (OIP3) near 2 GHz is measured to be +51.4 dBm while consuming only 899 mW of power (P_Dc), leading to a record Linearity Figure of Merit (OIP3/P_DC) of 154 which is roughly 5X higher than that of any RF amplifiers in use at these frequencies today. This amplifier design is enabled by 400 GHz InP Hetero- junction Bipolar Transistor (HBT) technology with multi-level interconnect technology and novel feedback circuit design to efficiently eliminate the nonlinearity while maintaining loop stability at high frequency. This successful demonstration shows a clear path toward power-efficient low-noise ultra-high-linearity (OIP3 > +60 dBm) RF amplifiers for future military systems.