In this thesis, two novel broadband slot mobile phone antenna designs respectively for penta-band WWAN operation and eight-band LTE/WWAN operation are presented. The antennas are suitable to be mounted near the bottom edge of the system ground plane of the mobile phone. Good radiation characteristics for the antennas are obtained, and the two antennas respectively occupy a small printed area of 50 ¡Ñ 4 mm2 and 53 ¡Ñ 4 mm2. The first design uses a C-shaped strip connected to the bottom edge of the system ground plane to make the structure of the system ground plane close to a symmetric shorted dipole antenna. This makes it promising to excite a chassis mode to enhance the operating bandwidth of the antenna. The second one uses a microstrip feedline having a chip-inductor-loaded branch. The novel microstrip feedline can lead to more uniform distribution of the electric fields excited in the slot such that enhanced bandwidth of the antenna¡¦s lower band is obtained. Further, since the chip inductor performs like a low-pass filter, the original bandwidth of the antenna¡¦s upper band is not affected. Additionaly, the impedance matching of the lower frequencies of the upper band can be improved, which enhances the upper-band bandwidth of the antenna. Effects of the user¡¦s head and hand on the proposed antenna are also studied, and the simulated SAR and HAC issues are also analyzed in this thesis.