Compact patch antenna for 2.4 GHz WLAN applications

Abstract

The length of a conventional wall-shorted PIFA can be reduced from $~λ_0/4$ to $~λ_0/16$ by a folding operation, which results in a double stacked shorted patch structure with a resonant frequency that can be controlled by modifying the distance among the stacked (upper, middle and lower) patches. A theoretical analysis based on a simple transmission line model is presented and compared with simulation results. The physical insight of the variation of the resonant frequency for this reduced-size antenna can be understood by considering the antenna as a shorted patch loaded with a capacitor. To overcome the bandwidth problem, we increase total height as a whole with tuning process. An experimental verification is carried out for a 9 mm × 9 mm × 11 mm two folded shorted patch prototype designed for the 2.4 GHz ISM band that can achieve a 7.36 dB (VSWR < 2.5) return loss bandwidth of 4% and results in a nearly omni-directional radiation pattern.