| In this thesis, two 70MHz, Q of 350 monolithic Gm-C bandpass filters (BPF) with low power consumption are presented. The integrated BPFs are intended to replace the bulky and expensive surface-acoustic-wave (SAW) filter in many high-performance wireless applications such as GSM heterodyne receivers for channel selection purpose. A structure using a simple low-Q bandpass network in the positive feedback loop for Q-enhancement is proposed and analyzed as a promising method to realize high-frequency, high-Q, low-power bandpass filters. The basic concept of this structure is to use a positive feedback with a gain of less than 1 to enhance Q. In this structure, there are two methods to realize high-order Q-enhance filters: first, cascading the 2nd-order Q-enhanced stages; second, cascading the low-Q bandpass networks in the feedback loop. Comparing these two high-order realizations, the first one has better attenuation to the blockers while the second one has better Q-enhancement efficiency, noise, linearity, and dynamic range (DR). Two filters with center frequency of 70MHz and Q of 350 are designed by using these two high-order realizations, respectively. The filters are fabricated in 0.25mum CMOS technology for verification and comparison among the calculated, simulated, and experimental performance. |
