Patent ID: 7126422

Claim:
A feed-forward amplifier having a distortion detecting circuit and a distortion cancelling circuit, wherein: said distortion detecting circuit comprises: a first linear signal path formed by first delay means; N first vector adjustment paths, said N being an integer equal to or greater than 2; a first dividing part for dividing the input signal to said distortion detecting circuit into two, the one of which is provided to said first linear signal path and the other of which is provided to said N first vector adjustment paths; N first frequency band signal extractors provided in said N first vector adjustment paths, respectively, for extracting signals of N discrete frequency bands; N first vector adjusters provided in said N first vector adjustment paths, respectively, for adjusting the phases and amplitudes of the output signals from said first frequency band signal extractors; a first multi-band signal amplifying part for amplifying the outputs from said N first vector adjusters, and a first combining part for combining the output from said first linear signal path and the output from said first multi-band signal amplifying part; and said distortion cancelling circuit comprises: a second linear signal path formed by second delay means; N second vector adjustment paths; N second frequency band signal extractors provided in said N second vector adjustment paths, respectively, for extracting signals of the same frequency bands as those of the signals extracted by said N first frequency band signal extractors; N second vector adjusters provided in said N second vector adjustment paths, respectively, for adjusting the phases and amplitudes of the output signals from said N second frequency band signal extractors; a second multi-band signal amplifying part for amplifying the outputs from said N second vector adjusters; and a second combining part for combining the output from said second linear signal path and the output from said second multi-band signal amplifying part; and wherein said first combining part of said distortion detecting circuit is formed by a combiner/divider for providing a sum component of and a difference component between the output from said first linear signal path and the output from said multi-band signal amplifying part to said second linear signal path and said N second vector adjustment paths, respectively.