Extremely compact dual-band PIFAs for MIMO application

A MIMO structure consisting of two extremely compact planar inverted-F antennas (PIFAs) (lambda/60 x lambda/20 x lambda/6) is proposed for GSM 900 MHz and 2.4 GHz wireless local area network applications. The miniaturisation of each antenna is achieved through a spiral-shaped PIFA and a capacitive load, forming a LC resonator. Both antennas have a good impedance bandwidth of 0.88-0.945 and 2.39-2.48 GHz for 0.9 and 2.4 GHz band, respectively. The two PIFA antennas are polarised orthogonally to each other, and isolation better than 228 dB is achieved in both bands without any structure etched on the ground. The predicted results are compared with the measured data and good agreement is found.