An Analog Predistorter with the In-Phase Modulator

This paper proposes a predistortion linearizer using the in-phase modulator. The harmonic generator of the proposed predistorter extracts a second harmonic signal. These signals are divided in-phase and quadrature- phase signals, and then amplifying each signals using variable gain amplifier. An in-phase modulator, modulate fundamental signal with second harmonic signals, generates the predistortion intermodulation distortion (IMD) signals and controls amplitude and phase of them with modulation factors. As a result, this predistorter is suppressed IMD signals of power amplifier effectively. The test results show that IMD3 is cancelled more than 20 dB in case of CW 2-tone signals with Deltaf=1 MHz. Also, it's improved the adjacent channel power ratio (ACPR) more than 6 dB for IS-95 CDMA 4FA signals.