Variable Phase Shifter Design for Analog Predistortion Power Amplifier Linearization System

This paper presents a variable phase shifter (VPS) designed and fabricated for an analog predistortion (APD) power amplifier (P A) linearization system. In this system, there are special demands on the VPS, which haven't been typical concerns in conventional VPS design. In our study, we focused on developing a VPS customized for APD linearization systems. This VPS has been fabricated in IBM 5P AE 0.35-mu m SiGe BiCMOS process, and its area is 0.594 x 0.240 mm(2). Measured results show that it has 90 degrees of total phase control from 0.7 GHz to 2.7 GHz, and shows a phase control curve with error less than +/- 1 degrees over a minimum 55.54 degrees tuning range. Also, the maximum frequency of phase control signal that can be modulated on an RF signal is 115 MHz, enabling a correction bandwidth up to 115 MHz in APD linearization systems.