Design methodology for image-reject low-power receivers for wireless communications

All receivers for wireless communications based on frequency down-conversion have to deal with the image band. The folding of image energy onto the carrier after down-conversion can significantly corrupt the signal-to-noise ratio of a receiver. Image-reject mixers remove the image energy providing performance in terms of gain, linearity and noise similar to a conventional mixer posing a better alternative to external/integrated image-reject band-pass filters. At present the image-injection-ratio (IRR) achievable with an IR mixer is approximately in the same order as the degree of rejection attained by an external band-pass filter. However, the stumbling block that prevents the widespread use of IR mixers as a feasible integrated alternative to external band-pass filtering is the higher power dissipation compared to a conventional mixer. The lack of a complete analysis in terms of IR receivers and their requirements in terms of IR on one side, and the lack of a design approach that optimizes the required IR and a minimal power consumption striking a balance between these two somewhat opposed parameters on the other side, have motivated this research work. This work contributes in the following three main topics: IR receiver architectures, CMOS mixers for operation in IR mixers and low-power CMOS IR mixers.