A 1.8-V CMOS direct-conversion tuner for mobile DTV applications

Abstract

A 1.8-V 0.18..m CMOS direct-conversion Tuner for UHF band mobile digital TV applications is presented. To meet the stringent requirements of Noise Figure (NF) and IIP3, a capacitor cross-coupled (CCC) common-gate LNA and a novel high-linearity, low-flicker noise Gilbert Mixer are adopted. The LNA achieves 26 dB variable gain by using digital controlled current-steering technique and a resistive attenuator. To overcome the gain roll-off at the high frequency channels, a current reuse self-biased post-LNA buffer is proposed as the interface between the VGLNA and Mixer. In addition, a fully integrated DC Offset Correction (DCOC) circuit with switchable high-pass corner frequency, is introduced to realize both low high-pass cutoff frequency and short settling time. A wideband integer-N synthesizer using an adaptive frequency calibration (AFC) of dichotomizing technique, settles less than 200 mus for LO generation. The tuner achieves 3.8 dB NF, 0dBm IIP3@20dB LNA gain attenuation, 92 dB gain dynamic range and occupies 3.45 mm times 3.4 mm silicon area, while drawing 59 mA from 1.8-V voltage supply.