A new Mismatch cancelation for Quadrature Delta Sigma Modulator

Abstract

This paper proposes a new mismatch cancelation technique for quadrature delta-sigma modulators (QDSM). In this approach, a high speed and simple structure dynamic element matching (DEM) based on homogenization and time-division (HTD) is designed. In addition, I and Q digital-to-analog converters (DACs) are merged into one complex DAC (C_DAC) for quadrature mismatch cancelation which leads to near-perfect I/Q balance. A third-order multi-bit continuous-time (CT) QDSM for a WCDMA LOW-IF receiver is designed and implemented in 180 nm CMOS technology to investigate the effects of the proposed DEM. The proposed DEM method and DWA algorithm are applied to the QDSM with 2% mismatch errors in DAC cells and compared two outputs PSD effects. Simulation results show that the modulator achieves a signal-to-noise ratio (SNR) of 74 dB and 74.2 dB for the proposed method and DWA, respectively, while the proposed method is simpler and faster than the data weighted averaging (DWA) algorithm.

Keywords

• mismatch shaping
• quadrature delta sigma modulator
• wcdma
• low-if receiver