Variable gain amplifier in polar loop modulation transmitter for EDGE

A variable gain amplifier and a polar loop modulation transmitter are presented. This variable gain amplifier is used to add amplitude modulation to a phase-modulated RF signal. For the circuit topology, CMOS inverter topology is adopted because of its good noise and linearity performances. Moreover, the basic inverter topology is modified to enlarge the variable gain range. From a PA point of view, the polar loop modulation transmitter is equivalent to a direct conversion transmitter, because their RF output signals have complete modulation information. The advantage of the polar loop modulation transmitter is that there is no VCO pulling problem.