Patent ID: 7403070

Claim:
A band selection type feed forward amplifier, 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; a first vector adjustment path; a first dividing part distributing an input signal to said first linear signal path and said first vector adjustment path; n first vector adjusters provided in said first vector adjustment path and adjusting the phase and amplitude of signals in respectively different frequency bands; a first switching means selecting one from among said n first vector adjusters and inserting the same into said first vector adjustment path; a first multiple frequency band amplifier amplifying the output of said first vector adjusters; and a combiner/divider respectively 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 amplifier; wherein said distortion elimination circuit comprises: a second linear signal path, constituted by a second delay means, into which said additive component is input; a second vector adjustment path into which said differential component is input; n second vector adjusters, provided in said second vector adjustment path and respectively adjusting the phase and amplitude of the signals in the same frequency bands as in said n first vector adjusters; a second switching means selecting one from among said n second vector adjusters and inserting the same into said second vector adjustment path; a second multiple frequency band amplifier amplifying the output of said second vector adjusters; 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 amplifier; N being an integer equal to or greater than 2; and comprising: a frequency controlling part switching and controlling said first switching means and said second switching means.