A LUT-free DC offset calibration method for removing the PGA-gain-correlated offset residue

Abstract

This paper presents a novel DC offset calibration method for the zero-IF (intermediate frequency) receiver that removes the PGA-gain-correlated offset residue. The conventional calibration method is usually based on the classic input/output referred offset model, in which the receiver IF programmable gain amplifiers (PGAs) have offset sources that varies a lot with different gain settings. Consequently, the conventional calibration method needs to generate the calibration code at each gain step and requires a huge look up table (LUT) to store the calibration values. This paper presents a new DC offset model which is gain non-correlated, by analyzing two types of commonly-used PGA. Based on the new model, a LUT-free single-step DC offset calibration method in together with the implementation circuit is designed. The proposed method has been verified on a practical zero-IF receiver circuit in a standard 0.18 μm CMOS technology through the Monte Carlo (MC) simulation. The simulation results show that the receiver IF output offset residue after calibration using the proposed method is reduced to below 12 mV, which is comparable to the LUT-based conventional calibration.