Abstarct: Over the past decades, the mextamaterials have attracted considerable attention in optics, physics and microwave engineering. These artificial structures, with simultaneous negative permittivity and permeability, possess unusual features such as supporting backward-wave propagation. Most mextamaterials suffer from important drawbacks such as a narrow frequency band of operation and lack the ability to control the electromagnetic properties. In this thesis, a magnetically tunable leaky-wave antenna consisting of composite right/left-handed unit-cells is presented. The structure is designed for beam-steering in forward and backward region for X-band applications. The tuning nature of the proposed structure is due to the dispersive permeability of the ferrite laxyer. Changing the external DC magnetic field changes the effective permeability of the ferrite and consequently the phase constant and the beam direction of the antenna. In most conventional structures of LWAs, the phase constant has only frequency dependence. This leads to challenges for RF sources and limits antennas usage in communication systems which require fixed frequency of operation. The proposed LWA is capable of both fixed-bias frequency scanning and fixed-frequency bias scanning.