Adaptive impedance matching and antenna tuning for green software-defined and cognitive radio
Impedance matching between the power amplifier and antenna is crucial for efficient power transfer in a green transmitter. A single antenna with a software-configurable tuning unit can serve the functions of multiple antennas which are otherwise required by multistandard wireless communications. Impedance matching and tuning must be adaptive and in real time for fast varying frequencies and surroundings of mobile communications. Small size and low power consumption must also be met in such tuning systems for mobile phones and terminals. This paper overviews automatic antenna tuning for modern and future generation mobile communications. Recent advances in impedance monitoring methods, fast tuning algorithms and programmable matching systems are discussed. Latest effort in integrating automatic impedance tuning systems on a silicon chip is also introduced.