A widely tunable active CMOS radio-frequency filter


There has always been a drive by industry to add as much functionality and flexibility to electronic devices as possible. Tunable circuits are among useful sub-blocks that facilitate achieving these goals. This thesis presents a fully integrated radio-frequency filter whose centre frequency and bandwidth are tunable. Radio-frequency filters are essential components in transceivers. However, due to the poor quality factor and large area of on-chip passive inductors, these blocks are typically implemented off-chip. The filter presented in this work uses active inductors, i.e., transistor-based structures that emulate the response of a passive inductor. Not only is the quality factor of an active inductor superior to that of its passive counterpart, but also its size is a relatively smaller fraction of the chip area. It should be noted that passive inductors have better performance in terms of noise, linearity, and power consumption as compared to their active counterparts. Special care has been taken to minimize the power, noise, and nonlinear distortions of the proposed filter. The filter is designed and fabricated in a 0.18pμm CMOS technology. Its centre frequency is tunable over the range of 580MHz to 3.3GHz and its quality factor can also be tuned, making it suitable for a variety of applications requiring different bandwidths. The fully differential filter, including the biasing circuitry and output buffers required to drive the 50Ω impedance of high-frequency measurement equipment, consumes between 12 to 26mW from a 1.8V supply and occupies a chip area of 115pμm x 70pμmApplied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat

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