Design of small antennas for multi frequency bands operation

Three single-feed microstrip patch antennas for multi-band operation are proposed in this paper. The first one is a planar inverted-F antenna (PIFA) with an L-shaped slit combined with a parasitic patch in co-planar geometry. It exhibits two operating frequency bands, which cover ISM bands (2.45 and 5.8 GHz) and U-NII bands (5.1, 5.2 and 5.8 GHz). There are four shorting pins inserted into the antenna. The second proposed antenna is a PIFA with a tilted slit and a shorting pin. It provides an impedance bandwidth which is wide enough to cover both IMT-2000 and 2.45 GHz ISM bands. The third antenna is a tri-band PIFA consisting of a U-shaped slot, one shorting pin and one shorting wall. It is able to generate three resonances (0.9, 1.8 and 2.45 GHz). Simulation and experimental results are given to verify the proposed antenna designs.