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A new triple band EBG unit cell with compact size has been designed, fabricated, and tested. The proposed EBG unit cell is based on a square mushroom-like EBG (M-EBG) structure with an interdigital coplanar waveguide (ICPW). With this technique, the size of the proposed ICPW-EBG structure has been reduced from λ/2 to λ/4 compared with the conventional M-EBG unit cell dimension, which is 18 × 18 mm2. The proposed unit cell was designed in order to respond for three frequency bands at 1.8 GHz, 2.45 GHz, and 3.7 GHz. An array of 10 × 10 unit cell was also designed as a reflector with an overall dimension of 181.8 × 181.8 mm2. The dipole antennas were implemented over the designed reflector with a short distance of λ/8 to radiate electromagnetic wave. The simulation results showed that the ICPW-EBG reflector can improve directivity of the dipole antenna to be 9.12 dB at 1.8 GHz, 9.02 dB at 2.45 GHz, and 8.40 dB at 3.7 GHz. The measurement directivities agreed well with simulation results including 8.72 dB at 1.8 GHz, 8.56 dB at 2.4 GHz, and 8.1 dB at 3.7 GHz. This is the first design of triple band EBG unit cell with 50% size reduction compared with the conventional structure at the same frequency. The designed ICPW-EBG reflector with dipole antenna results in the triple band operation, low-profile and high gain suitable for modern wireless communication systems.

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This research presents a metasurface reflector to support dual-band applications at 1.8 GHz and 5.5 GHz for LTE and WLAN, respectively. The proposed unit cell creating the metasurface has the property of an epsilon negative medium (ENG) that is one of the reflector requirements. The novel design of unit cells uses the ring resonator pattern associated with an interdigital capacitor to control resonant frequencies and relative permittivity. The epsilon negative medium can be controlled by using an interdigital capacitor that can create the electric field at the unit cell. Therefore, the size of the metasurface can be reduced from λ/2 to λ/4 which is much smaller than the conventional structure, resulting in a compact reflector when it works together with an antenna. The proposed unit cell was designed to obtain the dual-frequency operation with simulated bandwidth of 1.71 GHz -2.48 GHz at 1.8 GHz and 5.15 GHz -6.00 GHz at 5.5 GHz, respectively. The proposed metasurface was designed by using an array of 7×7 unit cells. The simulation and experimental results agree very well with the gains of 8.52 dB and 9.55 dB at 1.8 GHz and 5.5 GHz, respectively.