CURRENT MODULATOR WITH DYNAMIC AMPLIFIER IMPEDANCE COMPENSATION

摘要

An amplitude modulation circuit provides modulated supply current (IPA) possibly in combination with modulated supply voltage (VPA) to a radio frequency power amplifier (48) and includes a detection circuit (66) responsive to changes in the ratio of that voltage (VPA) to the modulated supply current (IPA), described herin as its AM modulation impedance. Such impedance (resistance) changes commonly arise from changing coupling characteristics at the antenna assembly (54) driven by the power amplifier (48). A gain control circuit may be associated with the detection circuit (66), and made responsive thereto, thus allowing adjustment of modulation gain control responsive to changes in AM modulation impendance.