Periodically Time-Varying Noise Cancellation for Filtering-by-Aliasing Receiver Front-Ends

Abstract

This paper presents a periodically time-varying (PTV) noise cancellation technique for filtering-by-aliasing (FA) receivers. The key to the proposed technique is the use of a time-varying transconductance (Gm) cell to sense the noise generated by the PTV resistor in an FA receiver while maintaining the sharp filtering offered by FA. A prototype IC fabricated in a 28-nm CMOS process improves the noise figure (NF) by about 3 dB while achieving over 67-dB stopband rejection with a transition bandwidth (BW) of only four times the RF BW. A minimum in-band NF of 3.2 dB and an average in-band NF of 4.2 dB are demonstrated. With an upfront N-path filter to further enhance the linearity, the measured out-of-band IIP3 is +18 dBm and the blocker 1-dB compression point is +9 dBm. The whole chip, including digital control circuitry, operates under a 0.9-V supply, while consuming 61-mW power at 500-MHz LO.