With recent advance in CMOS processes, many essential building blocks for wireless transceivers, such as low-noise amplifier (LNA), mixer, frequency synthesizer, channel selection filter and digital-to-analog converter, have been demonstrated using CMOS technology. However, process variation and path mismatch limit the image rejection performance of these building blocks. Extra building blocks are necessary to enhance the image rejection performance which is not desirable....[ Read more ]

With recent advance in CMOS processes, many essential building blocks for wireless transceivers, such as low-noise amplifier (LNA), mixer, frequency synthesizer, channel selection filter and digital-to-analog converter, have been demonstrated using CMOS technology. However, process variation and path mismatch limit the image rejection performance of these building blocks. Extra building blocks are necessary to enhance the image rejection performance which is not desirable.

In this thesis, the design considerations of a CMOS image reject mixer using Switched-Capacitor Hilbert Transformer are detailed. The Hilbert Transformer as the 90 degree phase shifter was implemented in Switched-Capacitor circuitry. Simulation results show more than 60dB image rejection can be achieved using the proposed image reject mixer. Such image rejection mixer can replace the conventional image rejection mixer without using the image rejection filter to provide further attenuation of the image signal. This can not only reduce the complexity of the system, but also relax the requirement of other building blocks. The designed mixer performs 18dB noise figure and 8dBm IIP₃ referring to 50Ω. The mixer achieves 67dB image rejection which more than the required 60dB for the whole system.