Patent ID: 6154664
Filing Date: 2000-11-28
Classification: H03F,H03G,H04B

Abstract:
A cellular phone for a mobile communications system, said phone being operable at a first radio frequency band and a second radio frequency band comprising a dual band transmitter and an antenna, said dual band transmitter comprising:a first power amplifier, said first power amplifier having a first input for a first signal at said first radio frequency band, a second input for a first control signal and a first output for an amplified first signal, said first output being connectable to said antenna;a second power amplifier, said second power amplifier having a third input for a second signal at said second radio frequency band, a fourth input for a second control signal and a second output for an amplified second signal, said second output being connectable to said antenna; anda control module, said control module being associated with said first and second outputs to receive a portion of one of said amplified first and second signals, and generating one of said first and second control signals to control one of said first and second power amplifiers, said control signal being a function of one of said first and second amplified signals and a reference signal, said control module comprising:a detector having an input for a portion of an amplified signal derived from one of said amplified first and second signals, and an output for a detection signal indicative of the power level of said amplified signal;a comparator having an input which receives said reference signal and having an input which receives said detection signal, said comparator generating an error signal corresponding to a difference between said reference signal and said detection signal; anda shaping circuit, said circuit weighing said error signal in accordance with a predetermined desired power characteristic to generate said control signal which accounts, at least in part, for nonlinear amplification characteristics of said power amplifiers.