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 (PDc), leading to a record Linearity Figure of Merit (OIP3/PDC) 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.