This paper presents a novel metamaterial based on Jerusalem cross structure with interdigital technique to be applied for dual-band systems. The proposed structure can operate at resonant frequencies of 1.8 and 5.5 GHz for LTE and WLAN bands, respectively. The interdigital structure was added to connect at the end of the Jerusalem cross structure in order to control the resonant frequencies and to promote for permittivity adjustment. The proposed metamaterial unit cell was designed to achieve the simulated dual-band operation with bandwidths of 1.70 ~ 1.95 GHz at 1.8 GHz and 5.06 ~ 6.04 GHz at 5.5 GHz, respectively. The unit cell size is reduced from λ/2 to λ/4 which is much smaller than the conventional structure. The 5×5 unit cells of metamaterials were implemented as a reflector for a dipole antenna resulting in dual-band operation with bandwidths of 1.58 ~ 1.88 GHz at 1.8 band and 5.05 ~ 5.68 GHz at 5.5 band, respectively. Besides, the dipole antenna with the proposed metamaterial reflector has measured gains up to 8.23 dBi at 1.8 GHz and 8.30 dBi at 5.5 GHz, respectively. Moreover, the shape of metamaterial structure is symmetrical, so it can be used for dual linear polarization. Also, the antenna with the proposed reflector has low profile with the distance of λ/8 between radiator and reflector. Therefore, the proposed metamaterial can be applied for any antenna applicable for LTE and WLAN applications.

Creating a Gain Enhancement Technique for a Conical Horn Antenna by Adding a Wire Medium Structure at the Aperture Conical Horn Antenna;Metamaterial;Wire Medium Structure; This paper proposes a technique for improving the conventional conical horn antenna for the X-band frequency using metamaterial on a wire medium structure. The main idea of this research is the application of the wire medium metamaterial to the conical horn's aperture for the enhancement of the horn's gain; this is done without changing the antenna's dimensions. The results show that the wire medium structure can increase the gain of a conventional conical horn antenna from approximately 17.7 dB to 20.9 dB (an increase of approximately 3.2 dB). A prototype antenna was fabricated, and its fundamental parameters including its reflection coefficient ($S_{11}$), radiation patterns, and directive gain were measured. The simulated and measured results were very good. The wire medium structure of the proposed antenna improved the radiation pattern, enhanced the directivity, increased the gain, and reduced the side lobe level using a simple integrated wire medium structure.

This paper proposes a frequency reconfigurable antenna system designed for cognitive radio applications. The antenna structure consists of a sensing antenna and a frequency reconfigurable antenna system. The sensing antenna scans the channel to discover frequency bands while the reconfigurable section is tuning to communicate within these bands. A reconfigurable antenna consists of five different patches and there frequencies cover from 2.1 GHz to 10.6 GHz. The frequency agility is achieved via a rotational motion of the patch antennas. The rotation is controlled by a stepping motor mounted on the back of the antenna structure and the motor's rotational motion is controlled by MEMS switch connected to a microcontroller. A frequency reconfigurable antenna offers many advantages such as easy fabrication, suitability for installation and coverage spectrum UWB (Ultra Wideband).

This research paper proposes a multi-band frequency selective surface (FSS) director using the aperture interdigital technique. The FSS unit cell has been designed based on a basic bandpass filter (BPF) connected with an interdigital structure. With the proposed structure, the FSS unit cell size can be reduced from $\lambda $ /2 to $\lambda $ /8 caused by the slow-wave effect of interdigital capacitance loaded at the end of the transmission line in the unit cell structure. Moreover, the capacitance loaded at the end of the transmission line can control the second and the third resonance frequencies to resonate as required. The unit cell has been designed at the fundamental frequency of 1.8 GHz and the controlled second and third resonance frequencies of 3.7 GHz and 5.2 GHz, respectively. The operating frequencies of the proposed FSS unit cell cover LTE band (0-1.9 GHz), Wi-MAX band (3.22GHz-4.7GHz), and WLAN band (5.15 GHz-5.95 GHz). The size of the unit cell is very compact which is 11.53 mm $\times10.77$ mm. The designed unit cells are then connected as an array of $8\times 8$ , resulting in an overall size of 92.31 mm $\times86.16$ mm. This array has been used as a director for dipole antennas designed at the frequencies of 1.8 GHz, 2.45 GHz, 3.7 GHz, and 5.2 GHz. From the simulation, the dipole antennas with the proposed FSS director have directional gains of 4.52 dB at 1.8 GHz, 3.83 dB at 3.7 GHz, and 3.29 dB at 5.2 GHz, respectively. Measurement results show the directional gains of 3.67 dB at 1.8 GHz, 3.16 at 3.7 GHz, and 3.42 dB at 5.2 GHz, respectively. The proposed FSS director has properties of multi-band operation with a compact size that can be developed for antenna covers and radomes of multi-band wireless communications.

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.

This paper presents dual-band multiple U-slotted microstrip patch antenna and a design of multiple frequency selective surface (FSS). It is screens with dissimilar periodicities for bandwidth enhancement, which are regulated by IEEE 802.11b/g and IEEE 802.16a for WLAN and WiMAX applications, respectively. The maximum gain at the resonant frequency of 2.45 GHz and 3.5 GHz are 9.3 dB and 7.3 dB, respectively. After implanting the FSS in the U-slot patch antenna it is found that the bandwidths have been improved from 6.12% to 7.35 % and 3.7% to 5.7% at resonant frequencies 2.45 GHz and 3.5 GHz, respectively.