Patent ID: 7460613
Filing Date: 2008-12-02
Classification: H03F

Abstract:
1. A method for a complex base-band adaptive digital nonlinear device model, comprising: processing in the nonlinear device model an input complex digital base-band I/Q signal through a plurality of cascaded digital function blocks, whereby each digital function block is used to minimize an error caused by a specific type of distortion between the nonlinear device model and an actual measured device performance, each digital function block being independent of other function blocks; time aligning a measured nonlinear device complex signal and the input complex digital base-band I/Q signal; adjusting one of the measured nonlinear device complex signal and the input complex digital base-band I/Q signal to achieve phase alignment by multiplying one of the signals by a phase adjustment value, whereby the digital nonlinear device model includes an AM-to-AM and AM-to-PM gain look-up table memory, the look-up table memory being read using an amplitude or power value of the input complex digital base-band I/Q signal, and a look-up value being provided to a complex multiplier which multiplies each input signal sample with an complex gain correction according to a measured device characteristic; and processing the multiplied complex digital base-band I/Q signal through a digital filter describing an impulse response resembling an actual nonlinear device frequency response to an envelope modulation, wherein the digital filter is found by signal processing equalizer techniques by comparing an input complex gain corrected signal with the measured device signal, wherein a gain of the digital filter is normalized to have an amplitude gain equal to one at zero frequency; and calculating new complex gain values for adaptation by comparing a measured digital nonlinear device signal with the processed input digital signal after the digital filter, wherein the complex gain look-up table and the digital filter are optimized in an adaptive way until a predetermined limit of difference of digital filter impulse response values or complex gain values between different adaptations is reached.