In this s ummary, we focus on the effect of mutual coupling between antennas in modelling MIMO in-door channel, for WLAN 5.4 GHz applications. Mutual coupling is derived from the rigorous electromagnetic analysis taking into account the specific dimensions and material constituting the antennas. Implementation of coupled antenna model is carried out within the Advanced Design System (ADS) of Agilent Electronic Design Automation (EDA) software. It enables one to analyse the effect of mutual coupling on the modulated s ignal flowing through the in-door MIMO channel under consideration. 1 INTRODUCTION Because of some compromise between performances and cost, processing and hardware have to be optimised. Hence, modelling accurately the overall communication path in modern wireless systems has become a strategic challenge. Electronic Design Automation (EDA) frameworks offer to designers more and more powerful software tools for achieving such goals. They provide mixed simulation of digital data and analogue signals up to the radio frequency. However, during the modelling stage, a designer has to implement the appropriate model to include all relevant effects. Different modelling levels may have some great impact on the simulation time and accuracy. In Multiple Input Multiple Output (MIMO) wireless systems, with the use of multiple antennas, the performance and the capacity of wireless systems are substantially improved. This is based on the assumption that the parallel subchannels are independent or uncorrelated. However, the physical limitations in portable devices imposes that multiple antennas to be closely spaced. This generates some considerable amount of mutual coupling between antenna elements. The mutual coupling i s significant and it may increase or decrease the correlation between individual subchannels, thus degrade or improve the MIMO system performances [1-4]. As a result, antennas should be carefully modelled in order to include these significant effects when considering the MIMO radio propagation channel. The present paper focuses on modelling the mutual coupling between antennas in a MIMO 2X2 in-door configuration.