Broadband quadrature-modulator with parallel switchable quadrature-generation

A new polyphase filtering topology is proposed which uses parallel switchable RC networks for accurate broadband 90 (degree) phasing. A 0.13 (mu)m CMOS prototype IC using the proposed quadrature-generation network in a directconversion quadrature-modulator achieves a measured image rejection ratio of -39 dBc or better in 0.6-2.5 GHz.