A New Fractal Based PIFA Antenna Design for MIMO Dual Band WLAN Applications

This paper introduces the design of a dual-band internal F-PIFA (Fractal Planar Inverted F-antenna) as a candidate for use in the dual band WLAN (wireless local area network) MIMO (multi-input multi-output) applications. At first, the 4th iteration Koch’s fractal geometry has been applied to the edges of the conventional rectangular patch structure to design a single compact antenna with a dual band resonant behavior. The radiating fractal based patch has been printed on a substrate with relative permittivity of 4.1 and thickness of 0.9 mm, and the antenna has been fed with 50 Ω probe. This antenna is located at the corner of a copper ground plane of 0.05 mm thickness and dimensions of 110×70mm2. It has been found that the resulting F-PIFA has the dimensions of about 21mm × 15mm × 6.2 mm, making it suitable for mobile terminal applications. Furthermore, the proposed antenna offers a dual band resonance with a frequency ratio of about 2.41; resulting in bandwidths, for return loss ≤ −10 dB, covering the two WLAN band standards. Modeling and performance evaluation of the proposed antenna have been carried out using the CST Microwave Studio. The modeled antenna has been applied to a 4 by 4 MIMO system suggested for use in dual band WLAN applications. Simulation results show that the suggested system offers ≤ −10 dB impedance bandwidths of about 300 MHz with an isolation of about 12 dB, for the lower band, and 570 MHz with an isolation of higher than 22 dB, for the upper band. This makes the proposed system suitable for use in MIMO dual band WLAN applications.