In this article, we present a solution of multi-access antenna with two ports, with operating frequency bands centered approximately on DCS and UMTS/ Wi-Fi standards. These two ports are isolated by using an original design method based on cavity approach. The innovation of the structure is from one hand, in its application in terms of flexibility, reconfigurability, portability for the future development of a unique system that allows cross services where telephony joined multimedia and online services. On the other hand, in the design method, i.e. the complete modal analysis of the antenna structure assumed as a cavity is exploited for designing such multi-access antenna. It is specifically extended here to different antenna topologies (considering either slots or short circuited configurations). The design method and the performances are validated through comparisons between simulations and measurements.