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Abstract
CPW-fed planar inverted-F antennas (PIFAs) with small ground plane for dual-band performance are proposed. The lower band and upper band can be selected independently: PIFA is for the lower band, and capacitively coupling slot is for the upper band. Moreover, the frequency ratio of upper band to lower band can be obtained from 1 to 3.1. The proposed antenna with wider frequency ratio will enable antenna engineer to design dual-band antenna easily. The radiation patterns for the lower band are decided by the PIFA with the quarter-wavelength electric L-shaped monopole patterns, and those for the upper band are dominant over the coupling slot with the half-wavelength magnetic dipole patterns. Hence, both patterns in the dual-band are near omni-directional. An antenna example is given for WLAN dual-band applications. Simulated data are consistent with the measured ones. Measured impedance bandwidth for 2.4 GHz band is 1090 MHz (47.9%), and that for 5 GHz band is 1180 MHz (20.6%). Additionally, through a suitable adjustment in antenna parameters, a wider bandwidth of 1970 MHz (51.2%) can be obtained with center frequency at 3.845 GHz. The radiation patterns and gains are also studied and analyzed.
