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An X-band reflectarray, which consists of double square loop loaded by spiral stubs (DSL-SS) unit, is investigated in this communication. The DSL-SS unit is composed of a modified double square loop loaded by four spiral stubs and is analyzed by a simple circuit approach, which can analyze the complex multiple resonance structure and guide the design, to reveal its characteristic. The reflectarray is designed according to a detailed design procedure and is then fabricated on a single-layer FR-4 substrate, which covers an area of 192×192 mm 2 . The proposed reflectarray has a wider gain bandwidth and lower cross-polarization when compared with the conventional single-layer reflectarrays, and its measured gain, the aperture efficiency and 1-dB gain bandwidth are 24.4 dBi, 53.5% at the center 10 GHz, and about 38% (9.4~13.2 GHz), respectively. This new reflectarray antenna is especially useful for low-cost broadband communication applications. Index Terms-Broadband antennas, reflectarray, resonance.0018-926X (c)

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A mechanically pattern reconfigurable dual‐band antenna with an omnidirectional radiation pattern or a directional pattern for 2.4/5GHz dual‐band WLAN application is presented. By manually rotating the top substrate, the antenna can operate at patch state or monopole state, respectively. A novel U‐gap structure consisting of an outer patch, an inner patch and a U‐shaped gap is introduced to achieve the dual band feature at both operation states. The measured overlapped bands of the two states are 2.4–2.56 GHz and 5.22–6 GHz, covering the 2.4–2.48 GHz and most of the 5.15–5.85 GHz WLAN band. The measured peak gain is 2.4 dBi at 2.5GHz, 6.2 dBi at 5.5 GHz for monopole state, and 5.8 dBi at 2.5 GHz, 7.2 dBi at 5.5 GHz for patch state.

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