Automatic phase alignment for a fully integrated Cartesian feedback power amplifier system

A phase-alignment system is used in the first reported IC to fully integrate a power amplifier, Cartesian feedback linearization circuitry, and a phase-alignment system. The phase-alignment system consumes 8.8 mW from a 2.5-V supply and employs a new technique for offset-free analog multiplication that enables it to function without manual trimming. Phase alignment of better than 9° is maintained for drifts as large as ±90°. We demonstrate how the phase-alignment system improves the stability margins of the fully integrated Cartesian feedback system. The power amplifier itself, integrated on the same die, operates at 2 GHz and delivers a maximum of 14.2 dBm of output power into a 50-Ω load. The IC was fabricated in a 0.25-μm CMOS process.