The AD8349 is a silicon, monolithic, RF quadrature modulator that is designed for use from 700 MHz to 2700 MHz. Its excellent phase accuracy and amplitude balance enable high performance direct RF modulation for communication systems. The differential LO input signal is buffered, and then split into an in-phase (I) signal and a quadrature-phase (Q) signal using a polyphase phase splitter. These two LO signals are further buffered and then mixed with the corresponding I channel and Q channel baseband signals in two Gilbert cell mixers. The mixers' outputs are then summed together in the output amplifier. The output amplifier is designed to drive 50 loads.