Abstract-In this paper, periodic structures are investigated in antenna design for wireless applications. These antennas were compared with CRLH miniaturization method. Three different models of patch antenna with coaxial feed on EBG ground, metamaterial substrate or EBG/AMC structure have been presented here. Also two compact dual-band antennas have been designed and fabricated based on CRLH techniques for wireless and GSM applications. The first antenna has directional pattern and operates at 1760, 2550 and 3850 MHz (three-band antenna) with gain 2.1, −3.9 and 2.5 dBi, and it is dual polarized. The size of prototype patch antenna is 20 × 20 mm 2 which is reduced about 47% in comparison to conventional patch antenna at 2.5 GHz. The second antenna is designed by the use of interdigital capacitor and spiral inductor. Dimensions of antenna are 15.5×12 mm 2 , so the size is reduced about 69% in comparison to conventional microstrip patch antennas at 1.8 GHz. The second tri-band antenna operates at 1060 MHz, 1800 MHz and 2500 MHz in which two frequencies (1.8 and 2.5 GHz) are suitable for GMS and WLAN applications. Both structures have been designed and fabricated on FR4 low cost substrate with ε r = 4.4 and thickness of 1.6 mm. All simulations are done with CST and HFSS. Equivalent circuit and experimental results are also presented and compared.

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Abstract-A novel fork monopole antenna is presented using metamaterial structures. The prototype monopole antenna consists of split-ring-resonators (SRR) as an electric-LC resonator and small ground. To prove the concept, the prototype antenna is designed and fabricated for wireless communication systems. The monopole structure makes ultra wideband (UWB) impedance bandwidth condition for 2-12 GHz. On the other hand, the prototype antenna shows dual notch band characteristics at 3.5-4.5 GHz and 5.3-6 GHz for WiMAX and WLAN rejection. The prototype antenna radiates omnidirectionally and has a gain altered between −4.5 and 6.2 dBi in 2.5-12 GHz, with an average gain of 4.2 dBi. The metamaterial model is suggested for the CRLH (ELC) resonator, and in addition, the parametric study for CRLH (ELC) resonator is presented for clarification of its manner on resonance controlling. Here, the final model antenna is fabricated on an FR-4, and experimental results are compared with simulations.

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The metamaterial elements and structures have been noticed for obtaining circular polarization (CP) while developing various procedures. In this paper, we have mentioned some of these cases and compared the metamaterial loads effect on antenna current distribution. We have classified them into four categories. The first case covers patch antenna based on composite right/left‐handed method, where the metamaterial has been used for changing the current distribution in the loop form. The second case has been achieved by radome and metasurface. In the third model, the interaction between feed and metamaterial load has been considered and the last case has been made by the metamaterial load with truncated structure. The metamaterial loading has been modeled based on Nicolson‐Ross or transmission/reflection techniques for extracting the permittivity and permeability. While the microstrip slot antennas are attractive for wider bandwidth, the truncated structure can change the current for achieving CP. Here, we have studied the antenna for wireless and WiMAX applications.

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