This doctoral thesis deals with monolithic active resonators and their use in high-frequency filters. The emphasis has been put on noise and distortion properties of active resonators, as these are crucial in potential applications. Two active resonator types are considered: passive LC resonators with active negative resistance compensation, and gyrator-based active inductor resonators.An introduction to the theory of passive resonators is given, and the basic quality factor and noise characteristics are discussed in detail. Filter structures based on parallel resonators are studied and techniques for frequency tuning briefly introduced.Based on a three-port equivalent, different negative resistor structures suitable for integration are categorized, and their fundamental small-signal and tuning properties derived. The noise properties of the topologies are analyzed and compared. The Volterra-series method is applied in the distortion estimations for each negative resistor type. Practical examples of integrated negative resistor are given with realistic measured data.High-Q active inductors based on integrated high-frequency gyrators are analyzed using the total loop phase shift as an essential parameter. Theoretical limitations of high-frequency performance and tuning are found. Noise and distortion properties are assessed in the same manner as with negative resistors to give grounds for direct comparisons. Practical issues of monolithic active inductor resonators are tackled and realized topologies with measured results are presented.Active resonator filters employing either of the resonator types are discussed. Their noise and distortion performance derived from the respective resonator results is calculated. Automated tuning techniques are briefly discussed. Exemplary designs are presented with measured data. The two realized active resonator filters with negative resistance resonators operate in the 3 – 4 GHz region with 1.1% and 12% relative bandwidths, 400-MHz tuning ranges, and 19-dB and 11-dB noise figures respectively. The DC power consumption is a low 15 mW per resonator. The active inductor filter has a center frequency of 2.4 GHz with almost 1-GHz tuning range. The noise figure is a high 30 dB as estimated by the theory.System considerations show that active filters cannot directly replace passive filters in traditional radio architectures due to their relatively poor performance, but as a new potential application, an LO signal generation system for direct-conversion transmitters with a monolithic band-pass filter is presented. Both GaAs and Si-BiCMOS realizations show the feasibility of the concept. With the comparable quality factors of 415 and 300 and approximately the same –1-dB output compression points of –20 dBm, the BiCMOS topology consumes only a fraction of DC power but still gives more than 80 dBc mirror rejection thanks to its dual-mixer topology.
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