Patent ID: 7649950

Claim:
An OFDM transmitter configured to perform a peak reduction process in a stepwise manner on a signal sequence to be transmitted to transmit a peak processed transmission signal, comprising: a dividing inverse fast Fourier transform unit configured to divide the signal sequence to be transmitted into N signal sequences and perform inverse fast Fourier transform on each of the divided signal sequences to output N time signal sequences, wherein N≧3; a threshold control unit configured to determine at least two threshold values used in the stepwise peak reduction process; a first peak reduction processing unit, including a first peak to average power ratio (PAPR) reduction control unit, a first cyclic shifting unit, and a first adder, wherein the first PAPR reduction control unit is configured to determine a first amount of cyclic shift to be applied to a first time signal sequence of the N time signal sequences based on a first one of the at least two threshold values, the first cyclic shifting unit is configured to apply cyclic shift to the first time signal sequence according to the determined first amount of cyclic shift, and to produce a first cyclically shifted time signal sequence, and the first adder is configured to add the first cyclically shifted time signal sequence and a second time signal sequence of the N time signal sequences to output a first peak processed time signal sequence, wherein the first amount of cyclic shift is selected from plural amounts of cyclic shift to minimize an exceeding power level over the first threshold value in the first peak processed time signal sequence; a second peak reduction processing unit, including a second PAPR reduction control unit, a second cyclic shifting unit, and a second adder, wherein the second PAPR reduction control unit is configured to determine a second amount of cyclic shift to be applied to a third time signal sequence of the N time signal sequences based on a second one of the at least two threshold values, the second cyclic shifting unit is configured to apply cyclic shift to the third time signal sequence according to the determined second amount of cyclic shift, and to produce a second cyclically shifted time signal sequence, and the second adder is configured to add the second cyclically shifted time signal sequence and the first peak processed time signal sequence to output a second peak processed signal sequence, wherein the second amount of cyclic shift is selected from plural amounts of cyclic shift so as to minimize an exceeding power level over the second threshold value in the second peak processed time signal sequence; and a power amplifier configured to amplify the second peak processed time signal sequence, wherein, the at least two threshold values are equal to or smaller than a saturated power level of the power amplifier.