New predistortion method using phase modulation with envelope signal

A new predistortion method using phase modulation technique is proposed. The phase modulator is adopted for generating predistortion signal. The phase of input signal is modulated with the envelope signal from the envelope detector then the IMD components are generated. Each coefficient of the 3/sup rd/ and 5/sup th/ order intermodulation distortion (IMD) is optimized to improve the linearity of the power amplifier. The amplitude and phase of IMD components are controlled in RF carrier band. This makes it possible to overcome several drawbacks of the envelope control methods such as difficulties in controlling the phase of baseband signal, narrow bandwidth, and delay variation at the low frequency circuits. The experimental results show the sufficient improvements in two-tone and multi-carrier CDMA test over the broad dynamic range.