Method and apparatus for linearizing an output signal

Abstract

The digital transmission sub-system comprises a DSP (100) which takes as its inputs the in-phase and quadrature channels of a baseband software radio stage. The in-phase and quadrature inputs are separately digitally predistorted (110, 120) and digitally up-converted (128) to the intermediate frequency (IF) band. The IF band signal is then converted (130) to an analogue signal which is up-converted to the radio frequency band at (134) prior to amplification at (140) to produce an RF output signal for radiation from an antenna. The predistors (110 and 120) predistort the incoming signals to counter distortion arising from the up-conversion and amplification processes within the transmission subsystem in order to linearise the RF output. The predistorters (110, 120) may be adapted using a feedback signal supplied to the DSP (100) from a splitter (142) at the output of the sub-system. The feedback mechanism may involve analogue correlation processes to permit the use of slower analogue to digital converters for providing the feedback to the DSP (100) (FIGS. 4 and 5).

Dependencies are inferred from the claim text.