Design of a high-gain N-path filter with harmonic rejection

Abstract

This paper presents an enhanced N-path filter architecture addressing the fundamental limitations of conventional designs in wireless communication systems. The proposed solution tackles two critical challenges: insufficient harmonic rejection and signal loss. By integrating a high-gain low-noise amplifier (LNA) at the input stage and implementing a novel transconductance amplifier-based weighted sinusoidal signal fitting technique, the filter achieves superior performance metrics. Implemented in SMIC 180 nm CMOS technology, the design demonstrates frequency tunability from 800 MHz to 1.2 GHz. Simulation results show third and fifth harmonic rejection ratios of 61 dB and 67 dB, respectively. The filter exhibits a gain of 21 dB with a noise figure of 8–9 dB and an IIP3 of \(-\)6.2 dBm. These results represent a significant advancement over traditional N-path filter implementations, offering promising prospects for practical wireless applications.