Wireless applications have grown significantly in recent years. The proliferation of their standards (LTE, 3G, WiFi, Bluetooth, GPS) is driving research toward yet more miniaturized circuits and reconfigurable architectures. The main goals are to reduce size, energy consumption and costs. In this context, our work presents a theoretical and experimental exploration of several technics to achieve this aim. On the one hand, the use of metamaterials allows the miniaturization of RF devices. On the other, the introduction of RF MEMS or ferroelectric materials enables the frequency agility at circuit level. After a theoretical review of metamaterials, planar structures in PCB technology have been experimentally studied in order to highlight the properties of the dispersion diagram. The results of design of a bandpass filter for space applications are then presented; the use of metamaterials has reduced its size by about 90% compared to a conventional quarter-wavelength stub filter. By using silicon technology, we are interested in the optimization of a cell based on the CRLH approach to increase its degree of freedom. In this work the adding of a capacitive stub, has been complemented by the introduction of RF MEMS to provide agility to this structure. The experimental results have demonstrated a tunability in the range of 80%. Similarly, another tuning technic based on the use of ferroelectric materials has been explored; thin BST films deposited on different substrates were used to extract the electromagnetic characteristics. Experimental work exhibited tunability of up to 67%. This study was finally completed by the realization of tunable metamaterial structures using BST.