| Summary: | A dual-band directional antenna for Industrial, Scientific, and Medical (ISM) band application is proposed in this article. The antenna consists of two layers of substrates. The first layer contains the square loop loading with a meander stub to realize the dual band. The second layer is a frequency selective surface (FSS) structure, which is a periodic array with square loops. The phase shift from the FSS reflection and the distance between two layers are optimized to realize the field superposition, which could achieve gain enhancement and bandwidth improvement at two operating bands, simultaneously. The measured results indicate that within a 2.3–2.62 GHz range and a 4.9–6.45 GHz range, the |S<sub>11</sub>| of the antenna is less than −10 dB. The −10 dB impedance bandwidth is 13% and 27%, respectively. The gain of the antenna is 6.8 dB at 2.45 GHz and 9.0 dB at 5.8 GHz. Meanwhile, the antenna gain is over 8.5 dB from 5.0 GHz to 6.0 GHz. The working band of the antenna covers all bands of WLAN. The design has a good application prospect in the future.
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