A dual-mode analog baseband utilizing digital-assisted calibration for WCDMA/GSM receivers

Abstract

A dual-mode analog baseband with digital-assisted calibration for WCDMA/GSM receivers is presented. The calibration includes automatic DC-offset Calibration (DCOC) and Automatic Frequency Tuning (AFT). The calibration circuits adopt low-complexity and small-area Digital-to-Analog convertors (DAC) that can achieve less than 5mV residual output offset combined with Successive Approximation algorithm (SAR). Every Programmable Gain Amplifier (PGA) stage has small DC-offset after DCOC without performance penalty and the measured IIP 2 is more than 60dBm. The cutoff frequency of Low Pass Filter (LPF) can be tuned very close to targeted value of 200 kHz and 2.1 MHz for GSM and WCDMA, respectively. The chip is manufactured in 0.13 !.1m CMOS technology with power supply of 1.5 V and occupies 1.2mm 2 silicon area excluding pads.I.

An effective DC offset calibration method combined with analog and digital circuits for direct conversion receivers

“…I n ; I p are the compensation currents of the differential DAC. The output DC offset voltage V osout can be expressed as follows [22,27,28]:…”