A fully integrated 900 MHz CMOS double quadrature downconverter

This paper presents a fully-integrated CMOS quadrature downconverter for use in high quality low-IF receivers. It has <0.3/spl deg/ phase error without any tuning or trimming. The downconversion is performed with a double quadrature structure. In this structure both RF and LO signals are put in quadrature and mixed down with four CMOS HF multipliers of which the output signals are combined two by two. The cross-coupling and combination of the four mixing products suppress amplitude and phase errors. The mirror signal crosstalk due to the phase errors of the quadrature generators of this structure is the square of the value of conventional structures.