Reconfigurable decoupling and matching network for a cognitive antenna

Cognitive radio applications require reconfigurable RF air interfaces. We present here the design of a reconfigurable decoupling and matching network (DMN) for a cognitive multi-band antenna array. The antenna array operates at three selected frequencies of GSM900, GSM1800 and IEEE 802.11b/g. The role of the DMN is to define radiation patterns at the input ports, decouple array elements, and improve return loss. In principle, each frequency would require its own DMN. However, our unified DMN combines three individual DMNs into a single circuit that can reconfigure the operational frequencies by changing the values of some elements. The antenna array is connected to the DMN by three switch elements providing the selection of proper array elements for a particular frequency.