Patent ID: 7634238

Claim:
A multi-band lookup table type predistorter for adding predistortion components for canceling distortion components produced by a power amplifier to an input transmitting signal and outputting the result comprising: N output side variable band signal extractors for extracting output signals in N frequency bands from output signals from the power amplifier, wherein N is an integer of 2 or greater; N input side variable band signal extractors for extracting transmitting signals in said N frequency bands from the input transmitting signal; N difference detectors for detecting differences between transmitting signals in N frequency bands and N output signals from said N output side variable band signal extractors; N lookup tables for reading distortion compensation data of corresponding N frequency bands by using differences of said N frequency bands as reference signals; N adders for adding the distortion compensation data read out from said N lookup tables to the transmitting signals in the corresponding N frequency bands; a combiner for combining the added outputs from said N adders and outputting the combined result as a transmitting signal with the predistortion; and a frequency band controller for controlling frequency bands of said N output side variable band signal extractors and said N output side variable band signal extractors commonly, wherein said frequency band controller comprises, a frequency band detector for detecting signals of N frequency bands from said input transmitting signal, and a band setting unit for controlling said N input side variable band signal extractors and said N output side variable band signal extractors based on said detected signals of the N frequency bands, wherein said frequency band detector comprises a sweep signal generator for generating a sweep signal, a local signal generator for generating a local oscillation signal whose frequency is swept according to said sweep signal, a mixer for multiplying said local oscillation signal by said input transmitting signal, and a low-pass filter for extracting direct current components from output from said mixer and outputting the direct current components as band detecting signal; and said band setting unit references said sweep signals and determines a lower limit frequency, an upper limit frequency and a center frequency of each of the N frequency bands from said band detecting signal and sets the lower limit frequency, the upper limit frequency and the center frequency to said N input side variable band signal extractors and said N output side variable band signal extractors.