CMOS gigahertz-band high-Q filters with automatic tuning circuitry for communication applications

Gigahertz-band CMOS front-end filters with high quality factors have been long considered as one of the most substantial and challenging building blocks in transceiver design. The filters have to satisfy stringent requirements for wireless standards, including gigahertz resonant frequency, high quality factor, low noise figure, high dynamic range, and excellent stability. Therefore, discrete components are usually utilized.; Considerable research has been conducted for two decades in developing high performance monolithic active filters to be implemented with other circuits onto the same chip. However, conventional Op-Amp based filters and state-of-the-art Gm-C filters cannot reach this goal because they are fundamentally frequency-limited implementation topologies; thus, only low hundred megahertz filters are reported to date. Furthermore, the characteristics of fully integrated analog filters usually deviate from the design specification due to process variation and temperature fluctuation, leading to performance errors. The master-and-slave scheme is a widely-used tuning circuitry for medium-Q video-band active filters. However, its tuning accuracy relies on the matching and tracking between both filters. Therefore, this tuning scheme is not suitable for gigahertz-band high-Q filters because parasitic capacitances cannot be matched well in such a high-frequency range.; To circumvent the aforementioned problems, we proposed three aggressive Gm filters and one RLC filter with Q-enhancement circuitry in this work, which essentially extend the filters' operation to gigahertz frequency range with reasonably high quality factors. A new image-reject filter is also demonstrated using this design technique. Based on tuning in the idle periods of the burst-mode transmissions and reception, a new synchronous rectification scheme is proposed to automatically correct the resonant frequency of filters. Since this scheme directly tunes the filters, it does not have matching and tracking problems. Furthermore, it consumes a smaller silicon area and little power. The proposed tuning scheme can also be utilized in lowpass, highpass, and notch filters.; A 1.15GHz high-Q RLC filter with a synchronous rectification tuning scheme has been designed, prototyped, and tested using 0.5um digital CMOS technology. The proposed filters indicated a great potential to be used in transceiver front-ends.