Adaptive digital pre-distortion circuit using adjacent channel power profile and method of operation

A wireless network capable of communicating with a plurality of mobile stations located in a coverage area of said wireless network, said wireless network comprising:

• a plurality of base stations capable of wirelessly communicating with said plurality of mobile stations, at least one of said plurality of base stations comprising an RF transmitter having an RF power amplifier required to transmit an RF output signal within selected limits of an adjacent channel power (ACP) profile specified for said RF transmitter, wherein said RF transmitter comprises a pre-distortion adjustment circuit comprising:
• input sampling means, coupled to an input of a transmit path of said RF transmitter, capable of capturing input samples from a digital input baseband signal, said input samples comprising a first input sample of amplitude X;
• output sampling means, coupled to an output of said transmit path, capable of capturing output samples of a digital output baseband signal derived from said RF output signal, wherein a first output sample corresponds to said first input sample;
• and
• processing means capable of determining from said first input sample and said first output sample a pre-distortion adjustment value capable of adjusting an amplitude of said digital input baseband signal prior to amplification by said RF power amplifier without causing said RF output signal to exceed said selected limits of said ACP profile.

For use in a wireless network comprising a plurality of base stations capable of communicating with a plurality of mobile stations, a method of operating an RF transmitter in one of the plurality of base stations, the RF transmitter comprising a transmit path capable of receiving a digital input baseband signal and generating therefrom a modulated RF output signal wherein the transmit path comprises an RF power amplifier operable to transmit the modulated RF output signal within selected limits of an adjacent channel power (ACP) profile specified for the RF transmitter, the method comprising the steps of:

• capturing from the digital input baseband signal a first input sample of amplitude X;
• demodulating the modulated RF output signal to thereby produce a digital output baseband signal;
• capturing a first output sample from the digital output baseband signal corresponding to the first input sample;
• and
• determining from the first input sample and the first output sample a pre-distortion adjustment value capable of adjusting an amplitude of the digital input baseband signal prior to amplification by the RF power amplifier without causing the modulated RF output signal to exceed the selected limits of the ACP profile.