A N-Path Receiver With Harmonic Response Suppression

TL;DR

This paper introduces a downconversion receiver with an N-path filter that suppresses harmonic responses at the 3rd and 5th LO harmonics, improving performance by reducing harmonic mixing and noise.

Contribution

It presents a novel switch-based N-path filter integrated in a feedback loop with PWM-LO clocking to suppress harmonic responses and mitigate blocker effects.

Findings

Effective suppression of 3rd and 5th harmonic responses.

Reduced noise injection around LO harmonics.

Improved blocker handling and frequency shift compensation.

Abstract

A downconversion receiver employing a switch-based N-path filter with reduced harmonic response around the third- and fifth- LO harmonics is presented. The N-path filter is placed in a frequency-translation feedback loop that is effective at the 3rd and the 5th LO harmonics to mitigate harmonic downconversion. A pulse-width-modulated LO (PWM-LO) clocking scheme is used in the feedback upconverter to reduce the noise injected around the LO harmonic at the input of N-path downconverter. The compression resulting from blockers around the 3rd and the 5th LO harmonics is also suppressed as a result of reduced harmonic response. Compensation of peak frequency shift of the N-path response due to parasitic input capacitance is also described.