Research And Implementation Of CMOS6-9GHz OFDM-UWB RF Transmitter

Ultra-wideband (UWB) targeting at the data rate up to1Gbps at2m with low power, high security and coexisting with other wireless systems is now in the ascendant of wireless communication technology for short distance. The multiband OFDM-UWB technology with flexible band configuration is expected as the market standard of UWB. This dissertation focuses on the design and implementation of CMOS6-9GHz OFDM-UWB RF transmitter as well as its integration in the transceiver.First, a nonlinear model with mismatches for OFDM-UWB transmitter is built. With this model, the output power spectrum of this transmitter can be calculated; the relationship between the spurs and the mismatches is revealed. Thus this model explains the basic principle of the RF transmitter and provides the rules of circuits design.By switching the resistor in the1st stage and the trans-conductors in each biquad of the LPF, a band-switching method is proposed to fulfill the requirement of dual-mode (MB-OFDM/DC-OFDM) operation. The measured cut-off frequency of the LPF (fc) is136MHz/272MHz at132-/264-MHz band respectively, the error is within3%. Meanwhile a MLL-based AFT is embedded to deal with the effects of the band-switching and the process variation on fc. The measurements show that the AFT can lock from90MHz to400MHz with an error less than5%, which indicates that the tolerance of fc variation is±40%.A current-mode transmitter is proposed to meet the requirement of integration the transmitter into monolithic SoC transceiver. It uses a current-mode LPF to replace the traditional voltage-mode one as the interface of the transmitter and DACs. The measurements validate the feasibility of the current-mode transmitter.Finally, a calibration method based on a self-mixing power detector with RSS1is proposed to reduce the power of the image and LO leakage.