Polynomial 2.1 GHz RF predistorter IC with envelope injection output
This paper presents the structure, test setup and measured results of a polynomial RF predistorter IC fabricated in a 0.35 mu m SiGe BiCMOS process. The predistorter is designed for the base station WCDMA band at 2.1 GHz. The predistortion signal is generated by a 5th-degree complex polynomial. Also a squared envelope is generated that can be used as a baseband injection signal to cancel 2nd-order distortion that typically causes memory effects. The performance of the predistorter was measured by driving a three-stage discrete power amplifier chain by a 2-tone test and a 3.84 MHz wide 3GPP WCDMA modulated signal. The 2-tone test showed more than 20 dB IM3 cancellation and the WCDMA signal's ACPR was improved by 8 dB.
envelope injection polynomial rf predistortion memory effects linearization