In this paper, an asymmetric compact multiband slot antenna is proposed for global positioning system (GPS), worldwide interoperability for microwave access (WiMAX), and wireless area network (WLAN) applications. The top plane, a ground is composed of a rectangular slot with a trapezoidal-like stub, an inverted U-shaped slot at the right side of the rectangular slot, an inverted L-shaped slot at the left side of the rectangular slot, and three stubs. The proposed antenna is fed by an asymmetric cross-parasitic strip on the bottom plane. By properly designing the slots and stubs, four resonant frequency bands are achieved with -10 dB reflection coefficient bandwidths of 50 MHz, 400 MHz, 390 MHz, and 830 MHz in the 1.57 GHz GPS band, 2.4 GHz WLAN band, 3.5 GHz WiMAX band, and 5.5 GHz WLAN bands, respectively. The antenna has a total compact size of 13 mm x 32 mm x 0.8 mm. Simulated and measured results indicate that the proposed antenna has sufficient bandwidth and good radiation performance in each band.

A variety of internal mobile phone antennas with a coupling feed are proposed. The antennas are suitable to be embedded in the mobile communication devices. At first, the coupling feed is incorporated to the conventional dual-band PIFA (planar inverted-F antenna) to achieve a dual-resonance excitation at about 900 MHz such that the obtained bandwidths can easily cover GSM850, GSM900, DCS and PCS operations. Then, the coupling feed is further applied to the PIFA with a single resonant path close to about one-eighth wavelength at 900 MHz. In this design, the large input impedance at 900 and 1900 MHz can be greatly decreased to allow the PIFA to generate two operating bands at about 900 and 1900 MHz to cover GSM900, DCS, PCS and UMTS operations. Finally, a compact quad-band folder-type mobile phone antenna with a coupling feed is proposed. The one-eighth wavelength mode can be excited, and the obtained bandwidths cover GSM850, GSM900, DCS and PCS operations.