Novel compact antenna designs for WiMAX (Worldwide interoperability for microwave access) operation in the mobile phone are presented in this thesis. In the first design, the antenna is integrated at one corner of system circuit board of the mobile phone and consists of two radiating portions; the monopole slot is formed by integrating the two portions. In the second design, two different antenna structures are used to achieve all WiMAX operating bands. Finally, in the third design, the chip antenna comprises a resonant monopole patch, a resonant shorter slot and a matching longer slot. The latter two slots are embedded within the monopole patch to achieve a compact integration. Detailed antenna designs and experimental results are presented and discussed.