A digital quadrature modulator with on-chip D/A converter

A digital quadrature modulator is presented that can replace the first analog IF mixer stage of a base station transmitter. It interpolates orthogonal input carriers by 16 and performs digital quadrature modulation at carrier frequencies f/sub s//4, - f/sub s//4 and - f/sub s//2. A 12-bit D/A converter are integrated on-chip using segmented current source architecture and a proper switching technique to reduce spurious components and to enhance dynamic performance. The modulator is designed to fulfil the spectral, phase, and EVM specifications of GSM, EDGE and WCDMA base stations.