Wideband decoupling and tunable matching networks for multi-port antennas

Cognitive radio is a very promising technology but it poses many challenges for the antenna system design. Apart from bandwidth limitations of small antennas, additional requirements emerge from the goal to replace conventional frequency duplexers by tunable filters and high dynamic range RF front ends. In this paper, we present a systematic design procedure for matching and decoupling multi-port antennas with a focus of achieving the highest possible isolation between antenna ports. An important aspect of the approach is the introduction of pre-matching circuitry between the antenna and the decoupling network. The novelty resides in the wide frequency range over which the decoupling network is applicable in connection with low complexity electrical tuning circuitry.