Method and apparatus for linear amplification of a radio frequency signal

This invention is generally related to amplifiers and, in particular, to linear amplifiers. A method and apparatus is provided that amplitude modulates a modulated radio frequency (RF) signal () by modulating the supply voltage of a power amplifier (). The method and apparatus further provides an impedance modulator () that reduces output signal () errors in response to an error signal generated by a feedback circuit () that includes a quadrature modulator (), a limiter (), a comparator (), and a quadrature downconverter (). Intermodulation distortion generated in the feedback circuit () by delay mismatches between amplitude and phase feedback paths, and non-linear effects of AM/PM conversion in a limiter (), are suppressed by placing limiter () and quadrature downconverter () in a forward path of the overall amplifier loop.