LINEAR AMPLITUDE MODULATION IN A POLAR LOOP CONTROL CIRCUIT

摘要

According to the invention, the linearity of a transmitter stage of a mobile phone is increased by modulating the supply voltage of a power amplifier (PA) using a controlled voltage source (Ubatt modulator). The voltage modulator is controlled by an amplitude comparator that compares the input signal (Udes) with the output signal (Uout). The invention thereby allows to avoid the dependency of the loop bandwidth of the polar loop of the size of the output signal Uout and thus a deterioration of the spectrum.