A CMOS adaptive antenna-impedance-tuning IC operating in the 850MHz-to-2GHz band

Adaptive antenna-tuning units (AATUs) provide broadband dynamic tuning to widely-varying antenna impedances caused by the changes in operating frequencies and unpredictable environmental factors. AATUs are becoming a critical need in multimode transceivers, since they minimize the power reflection due to the impedance mismatch between PA/LNA and antenna at various frequencies. AATUs also enable low-cost, bandwidth-limited and low-profile antennas to be used in multiband radios. One of the fundamental requirements for AATUs is fast tuning speed to compensate for the frequent changes in operating environment and frequencies, while keeping the power consumption as low as possible. In state-of-the-art AATUs, the sensed mismatch signal is converted to the digital domain utilizing high-speed analog-to-digital converters (ADCs) to enable fast tuning [1–3]. These ADCs either consume high power or they are low resolution, which results in compromised tuning performance. In this paper, an AATU utilizing analog mismatch detection and mixed-signal matching-state search circuits operating in a frequency band from 850MHz to 2GHz is presented. The module is implemented in a 0.18µm CMOS process and runs on a search algorithm that guarantees the optimum matching condition between the antenna and front-end circuits.