Patent ID: 7336128

Claim:
A feed forward amplifier for multiple frequency bands, having a distortion detection circuit and a distortion elimination circuit, wherein said distortion detection circuit comprises: a first linear signal path constituted by a first delay means; N first vector adjustment paths; a first dividing part dividing an input signal into said first linear signal path and said N first vector adjustment paths; N first variable frequency band extractors provided respectively for each said first vector adjustment path, and extracting signals of mutually discrete frequency bands; N first vector adjusters provided respectively for each said first vector adjustment path, and adjusting the phase and the amplitude thereof; a first multiple frequency band amplifying part amplifying the output of each first vector adjuster of said first vector adjustment paths; and a combiner/divider outputting the additive component and the differential component of the output of said first linear signal path and the output of said first multiple frequency band amplifying part; wherein said distortion elimination circuit comprises: a second linear signal path, constituted by a second delay means, into which said additive component is input; N second vector adjustment paths into which said differential component is input; N second variable frequency band extractors, respectively provided for each said second vector adjustment path, extracting the signals of respectively the same frequency bands as said N first variable frequency band extractors; N second vector adjusters, respectively provided for each said second vector adjustment path, and adjusting the phase and the amplitude thereof; a second multiple frequency band amplifying part amplifying the outputs of the second vector adjusters of said second vector adjustment paths; and a second combining part combining and outputting the output of said second linear signal path and the output of said second multiple frequency band amplifying part; N being an integer equal to or greater than 2; and comprising: a frequency band controller controlling said N first variable-frequency band extractors and said N second variable frequency band extractors.