A 1.25mW 75dB-SFDR CT filter with in-band noise reduction

Abstract

In a direct-conversion wireless receiver the baseband filter should be able to handle large blockers, resulting in a very challenging spurious free dynamic range (SFDR) requirement. In particular, the noise added in-band trades off with the linearity required to handle close out-of-band interferers [1]. Since the integrated noise generally is proportional to kT/C, once the noise floor for the filter is set, the amount of capacitance is roughly defined as well as a lower bound for area and power consumption. The solution presented in this paper aims to break this trade off by inserting an in-band zero in the output noise transfer function to improve the dynamic range.