A method to tilt the beam of a planar antenna in the E‐plane is demonstrated by implementing a metamaterial (MM) structure onto the antenna substrate at the fifth‐generation (5G) band of 3.5 GHz. The beam tilting is achieved due to the phase change that occurs when the electromagnetic (EM) wave traverses through two media with different refractive indices. A new adjacent square‐shaped resonator (ASSR) structure is proposed to achieve the beam tilting in a dipole antenna. This structure provides a very low loss of −0.2 dB at 3.17 GHz. The simulation and measurement results illustrate that the radiation beam of the dipole antenna is tilted by +25° and −24° depending on the position of the ASSR array onto the dipole antenna substrate. In addition, no degradation in the gain is observed as in the conventional beam‐tilting methods; in fact, gain enhancement values of 3 dB (positive deflection) and 2.7 dB (negative deflection) are obtained compared with that of a dipole antenna with no ASSR array. The reflection coefficient of the dipole antenna with ASSR array has a good agreement with that of the dipole antenna with no ASSR array. The measured results agree well with the simulated ones.

The incorporation of Electromagnetic Band Gap (EBG) unit cells, a type of metamaterials, with a dual band array antenna is proposed. By configuring the band gap of EBG cells accordingly, the pattern of the array antenna is successfully reconfigured at lower band of 2.4 GHz while maintaining the pattern at higher band of 5.8 GHz. Three pattern directions have been achieved: initial radiation pattern, 349-degree shift and 11-degree shift of the H-field. The array antenna is also frequency reconfigurable by suppressing the radiation pattern of the antenna in four different EBG cells configurations. In pattern shifting mode, the realized gain of the antenna is satisfactorily maintained and is comparable with the standalone of dual band array antenna with the range of gains from 5.08 dBi to 6.14 dBi and 7.83 dBi at 5.8 GHz.

Dual mode modified double square ring resonator (MDSRR) operating at 76 GHz millimeter‐wave has been simulated, and experimentally verified. MDSRR structure operates in two modes, metamaterial (MTM) mode and frequency selective surface (FSS) mode, depending on the direction of the electric field. The MDSRR in the MTM mode performs well at the desired frequency region by providing the highest insertion loss, S21, as reported in the literature with a loss of −0.5 dB. The electromagnetically induced transparency principle is applied to explain the loss reduction mechanism. The low losses MTM structure has the potential to enhance the performance of the radiating elements of the automotive radar systems. Conversely, in the FSS mode, the FSS characteristics of the proposed structure are numerically simulated and verified experimentally by changing the direction of the electric field along the x‐direction, in which the structure shows opposite behavior compared to the MTM performance. To demonstrate the validity of the FSS characteristics, the MDSRRs structure was tested using a waveguide measurement facility. The experiment results match well with that of the simulation, and wideband‐stop characteristics are introduced in the range of 74 GHz to 80.3 GHz.

This paper aims to produce a high data capacity and miniaturized flexible chipless RFID tag based on the frequency signature using the Modified Complementary Split Ring Resonator (MCSRR). The proposed 19 bits chipless RFID tag using the frequency shifting technique consists of five slotted overlaying MCSRR with Different Width (MCSRR with DW) structures and the dimension of 48 mm × 48 mm. The structure is designed by using a flexible (Polyethylene Terephthalate ) PET substrate with permittivity of 0.2. The operating frequency is between 0.9 GHz and 2.7 GHz. The advancement of slotted overlaying MCSRR with DW structures has successfully miniaturized the chipless RFID tag structure to about 107 mm 2 / bit, 0.02λ 2 mid /bit and 0.09 GHz/bit by maximizing the number of resonators in a limited space and minimizing the frequency separation between the resonators. The omnidirectional tag antenna is incorporated with the proposed MCSRR structure using the retransmission measurement method. The log-periodic antenna with a gain of 5-7 dBi is used for this measurement to improve the range distance between tag and reader system. Based on the retransmission measurement involving the antenna tag, the 19 bits chipless RFID tag which consists of five MCSRR with DW structures can be detected with a maximum range distance of 30 cm and a power transmitted level of 30 dBm.INDEX TERMS Flexible chipless RFID tag, metamaterial, split ring resonator (SRR), retransmission method and size miniaturization.

This paper presents a study of bending a metamaterial based absorber. The study of bending is important for textile material since it can be easily crumpled. The basic absorber that is simulated for the study is an annulled circle as the top patch, and metal ground plane that sandwich a textile-based substrate. The center frequency for the absorber is 10.525 GHz. The type of bending is divided into two parts, which is convex bending and concave bending. Through series of simulations, the effects of the bending on the absorptivity and the shifting of the resonant frequency is observed. Also, the study on the change of incident and polarization angle is also included to support the basis of flexible metamaterial absorber affected by the bending.

In this paper, a wideband multilayer transmitarray antenna is designed for Ku frequency band. The unit cell is designed at 12GHz using frequency selective surface structure. A new double square ring with center patch based multilayer unit cell has been designed and simulated. Then, the effect of substrate thickness variation on transmission coefficient magnitude and phase range is discussed. In the final design, the horn antenna designed at Xband is used as a feed source for transmitarray antenna. The simulation results show a wide impedance bandwidth from 10 to 13GHz. Besides, a wider gain bandwidth of 1.975GHz with a peak gain of 19dB is also achieved. All simulation results have been verified by the measurement. The proposed transmitarray design will find applications in high gain, directional and low profile antennas for X-band communication systems.

<p>This paper presented the bandstop Koch fractal hexagonal loop frequency selective surface (FSS) for the X-band application. The simulated transmission coefficient response (S_21) had been obtained by using CST software. The proposed Koch fractal hexagonal loop FSS structure is highly insensitive towards angular stability and also incident polarization up to 60 degree , with deviation of resonant frequency,  f_r below than 1%. The parametric analysis on the effect of the periodicity, width, and height of the fractal FSS structure on the S_21 has been illustrated and discussed thoroughly.</p>

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