A multicarrier QAM-modulator for WCDMA basestation with on-chip D/A converter

A multicarrier QAM modulator for a wideband code division multiple access (WCDMA) basestation has been designed. The multicarrier modulator performs pulse shaping filtering for four baseband I and Q data streams. Input data is interpolated in four stages each interpolating by a factor two. Four independent carriers are generated and modulated with the CORDIC based numerically controlled oscillators (NCOs) and summed up to form a multicarrier WCDMA signal. SINC-attenuation effect of a D/A converter is canceled by an inverse-SINC predistortion filter. The multicarrier signal is converted to the analog domain with a 14-bit current steering D/A converter which is integrated on the same silicon chip. Process used in realization of the chip is a 0.35 μm BiCMOS process. However, only CMOS transistors are used