An individual order predistorter based on diode series feedback using controlling bias voltages

In this paper, a third- and fifth-order analog predistorter using series feedback constituted individual predistorter of common-emitter amplifiers and schottky diodes has been developed. The individual order predistorters of the proposed circuit have shown the gain and phase control characteristics in order to compensate nonlinearity of amplifier with wide dynamic range. The individual predistorters with improvement of AM/AM and AM/PM is controlled the optimum condition of third- and fifth-IMD by the diode bias. The proposed circuit consists of the individual predistorters, power splitter and divider. The test results show that the third- and fifth-IMD of power amplifier is cancelled maximum 13.5 dB and 13.4 dB for two-tone signals, respectively. Also, it´s improved the adjacent channel leakage ratio (ACLR) approximate 2.5 dB and 3 dB each other for CDMA 2FA signals at 1.23 MHz and 1.98 MHz offset points. The proposed predistorter provides moderate distortion improvement and control individual-orders at little extra cost. It also is realized with advantages of miniaturized size, low complexity, and stable operation.