Bilayer miniature broadband microstrip patch antenna with Minkowski fractal

A novel broadband microstrip patch antenna is proposed and studied. The antenna achieves broadband through adopting bilayer patch for coupling and what´s more, a capacitive metal-wafer is introduced on the top of feeding probe to counteract the inductance caused by the probe. In addition, Minkowski fractal-patch structure is applied in antenna design to realize its miniaturization. The antenna performance has been simulated and analyzed on condition that antenna patches are in first-order fractal. Finally, a miniature bilayer microstrip patch antenna operating at 3.5 GHz is designed and its prototype has been manufactured and measured in anechoic chamber. Both the simulated and measured results show that the proposed antenna can synchronously achieve miniaturization and wideband. The side length of the larger patch is 28% of free space wavelength of the lowest operating frequency. Reflection coefficient is lower than -10 dB in 3.33-4.0 GHz and the impedance bandwidth is 18.3%. Moreover, antenna gain is stable and higher than 6.5 dBi during the band. Therefore, the antenna characteristics can well satisfy the requirements of WiMAX systems.