Digital feedforward amplifier for use in an RF transmitter and method of operation

A wireless communication system comprising a plurality of base stations operable to communicate with a plurality of mobile units, wherein at least one of said plurality of base stations includes a digital feedforward amplification system comprising:

• a first branch comprising:
• a digital combiner circuit capable of receiving a plurality of digital input signals and generating from at least one of said plurality of digital input signals at least one digital composite output signal;
• a DAC circuit for receiving said at least one digital composite output signal and converting said at least one digital composite output signal to at least one analog composite output signal;
• a modulation circuit capable of receiving a local RF signal and said at least one analog composite output signal and generating therefrom a modulated RF signal;
• and
• a power amplifier capable of amplifying said modulated RF carrier signal to produce an amplified RF output signal;
• a second branch comprising a distortion correction circuit capable of receiving said at least one digital composite output signal from said digital combiner circuit and generating a correction signal capable of at least partially canceling a distortion signal introduced into said amplified RF output signal by said power amplifier in said first branch;
• and
• a combiner circuit capable of combining said amplified RF output signal and said correction signal to thereby at least partially cancel said distortion signal.

For use in a transmitter in a wireless network, a method for generating an RF output signal comprising the steps of:

• combining one or more of a plurality of digital input signals to produce at least one digital composite output signal;
• converting the at least one digital composite output signal to at least one analog composite output signal;
• modulating a local RF signal with the at least one analog composite output signal to produce a modulated RF signal;
• amplifying the RF modulated signal to produce an amplified RF output signal;
• and
• generating from the at least one digital composite output signal a correction signal capable of at least partially canceling a distortion signal introduced into the amplified RF output signal by the step of amplifying.