CMOS Impedance Transforming Balun Filter with Improvement of Magnetic Coupling to Nearby Spiral Inductors

Abstract

This paper presents a novel balun filter in TSMC 0.18 mu m CMOS technology which can suppress the magnetic coupling with nearby on-chip spiral inductors. The proposed balun filter keeps major requirements of a traditional coupled spiral inductor balun used in the output stage of a PA (power amplifier) such as center tap for DC bias, controllable impedance transformation ratio, good out-of-phase performance, etc. This new structure can achieve a maximum of 18 dB suppression of magnetic coupling to the nearby spiral inductor.