| The expansion of mobile communication market has been remarkable. From originally providing voice service, the wireless industry has gradually evolved to enable high bit-rate multi-media communications. Within the next generation (3G) framework, the WCDMA system has emerged as a standard.; There is enormous pressure to reduce the size, cost and power consumption of the cellular handsets. While digital circuits have experienced tremendous power saving and enhanced functionalities with the progress of deep sub-micron processes, the analog/RF sections remain the bottleneck. This dissertation focuses on the design of a highly-integrated low-power transmitter IC (TxIC) in a 0.25 mum SiGe BiCMOS technology for the WCDMA handset applications.; The TxIC employs an improved highly-integrated digital-IF architecture. Excellent EVM performance is achieved due to the inherently mismatch-free digital quadrature modulation. The architecture eliminates the external IF SAW filter by adopting an optimal frequency plan and a special-purpose D/A conversion scheme which produces high-order sin(x)/x rolloff. Spurious emission requirements are then met with no dedicated reconstruction filter circuits. As the D/A boundary is shifted closer to the antenna, the architecture will take full advantage of future CMOS technology scaling.; Smart-power circuit techniques are researched. A high-speed DAC is designed to drive a dominantly capacitive load employing very low bias current. The up-conversion mixer, by means of a translinear transconductor, will effectively scale down the power usage for gain control. The RF amplifier features an adaptive bias scheme based on a power detector circuit, so that high linearity can be simultaneously achieved with high efficiency.; To provide further linearity improvement without increasing the quiescent current consumption, a linearization technique based on envelope signal injection is proposed. It is analyzed rigorously using the Volterra method, and the theoretical predications match very well with the measured and simulated results.; Experimentations on the fabricated TxIC chip have confirmed its correct functionality in all aspects, with state-of-the-art performance that meets WCDMA transmission requirements. It also compares very favorably to other published work in terms of level of integration and power consumption. |
