A 3 V GSM baseband transmitter

A dual-channel baseband transmitter has been designed for GSM cellular phone application. It has been fabricated in a 0.35 /spl mu/m digital CMOS process as part of a single-chip solution for baseband processing. Each channel consists of a switched-capacitor DAC, a switched-capacitor filter, a class AB buffer, and an active RC filter. The lack of on-chip precision capacitors and resistors poses a major challenge in designing these analog building blocks. The current consumption is 8.8 mA and the total active area is 5.1 mm/sup 2/. The channel response meets the GMSK spectral mask, and a real GSM call has been made with this transmitter.