A Harmonic Rejecting N -Path Filter with Harmonic Gain Calibration Technique

In this paper, an improved harmonic rejecting N -path filter with a circuit-level structure is proposed. A different set of mixing functions is introduced to conventional N -path filters. Systematic analysis shows that the mixing functions have the benefits of harmonic rejection at the radio frequency node. An 8-path circuit-level structure is proposed, and a harmonic gain calibration technique is introduced to calibrate the errors due to the process variation and mismatch. The proposed 8-path filter is designed and simulated under the 65-nm CMOS technology and achieves 17– 29 dB gain with a 2nd harmonic rejection ratio of 24– 31 dB , 3rd – 6th harmonic rejection ratio of 35– 60 dB , a frequency range of 0.1– 1GHz , and a noise figure of 3.8– 4.9 dB.