An efficient method for improving the mutual coupling between two antipodal Fermi-based tapered slot antennas is presented. This is achieved by using metamaterial-based corrugations, acting as a ...metasurface shield, etched on edge side of the substrate. An array of split-ring resonator unit cells is incorporated into the design to suppress leakage from the side walls and to improve the isolation. The effect of metasurface corrugations results in a mutual coupling improvement of 12-15 dB over a frequency band from 27 to 32 GHz. Moreover, the radiation characteristic of the proposed antenna is not affected, leading to a higher gain and improved total efficiency with low mutual coupling. The proposed antenna is a suitable candidate for 28 GHz multiple-input-multiple-output (MIMO) systems. The measured isolation of the prototype antenna varies from -37.1 to -49.8 dB along with a measured gain of 16.13-17.92 dB over an operating frequency band from 27 to 32 GHz.
In this letter, a new frequency-selective absorber is presented that has wideband transmission/absorption/reflection reduction responses. The presented absorber is completed by lossy cross-dog-bone ...and lossless second-order frequency-selective surfaces. The modal interaction pole generated by the lossy array is employed to achieve a wideband transmission. Three absorption bands are combined to realize a continuous stopband with high absorptivity. Furthermore, the improved absorber structure is investigated to reduce the strong reflection between the absorption and transmission bands. The 10 dB reflection reduction is obtained with a fractional bandwidth of 126.4%. Meanwhile, the -3 dB fractional passband width is 41.3% with minimum insertion loss of 0.37 dB. The absorption bandwidth of 91.5% is provided with at least 90% absorptivity. The distance between the lossy and lossless layers is only 0.08 <inline-formula><tex-math notation="LaTeX">\lambda _{L}</tex-math></inline-formula> at the lowest operating frequency. Finally, the proposed design is validated by a good agreement between the numerical simulations and experimental measurements.
A new wideband and enhanced gain Fabry-Pérot cavity antenna is presented in this letter. The Fabry-Pérot cavity is established between a single-layer metamaterial-based partially reflective surface ...(PRS) and a simple feeding slot antenna. The unit cell of the PRS consists of printed and etched square rings on both sides of the superstrate. A 6 × 6 array of the unit cells is optimized to produce a positive reflection phase gradient required for the gain enhancement. Simulated results of the designed Ku-band antenna demonstrate an impedance bandwidth of 13.1-15.3 GHz (15.5%) with a gain enhancement up to 8.2 dB (i.e., 150% gain increase above the feeding antenna) and a 3 dB radiation bandwidth of 18.7%. Experimentally observed reflection and radiation responses of the fabricated prototype validate the simulated results.
In this letter, a dual-plane beam-sweeping dielectric resonator antenna (DRA) using cantilever enabled frequency selective surfaces (FSSs) is presented. The proposed antenna consists of a ...conventional cylindrical DRA and a hexagonally arranged active FSS operating at 30 GHz frequency band. Initially, the reconfigurable FSS using cantilever beams is designed and analyzed. Furthermore, a prototype of the proposed antenna with FSS is designed, fabricated, and measured. The beam sweeping is obtained in both azimuth and elevation planes of the antenna. The whole azimuth plane is covered by the switched beams in six steps of an angle of 60 <inline-formula> <tex-math notation="LaTeX">^\circ</tex-math></inline-formula>. In the elevation plane, two steps of angles are obtained at 90 <inline-formula><tex-math notation="LaTeX">^\circ</tex-math></inline-formula> and 30<inline-formula> <tex-math notation="LaTeX">^\circ</tex-math></inline-formula>. The measured antenna gain of 8.1 dB is obtained.
In this letter, a dual-polarized frequency-selective absorptive structure is presented with two wideband transmission windows. The transmission windows are achieved within a wide -10-dB reflection ...band. At the frequencies of the passbands, the out-of-phase currents are excited without flowing through the lossy elements. Therefore, the passbands can be obtained with high transmittance. Moreover, only four resistors are loaded on each unit cell to consume the out-of-band reflective wave. By combining lossy flower-shaped and lossless arrays together, the desired dual-band and low reflection performances can be realized. Within the operating band, the reflection is below -10 dB with the fractional bandwidth of 127%. Meanwhile, around 6.5 and 12 GHz, the passband widths are 39% and 40% and the corresponding insertion losses are 0.07 and 0.1 dB, respectively. Finally, the fabricated prototype is measured to demonstrate the feasibility of the presented method.
This letter presents a new design of tilted-beam antenna with gain enhancement based on the multilayer frequency selective surfaces (FSSs) for fifth-generation applications. A dual-sided printed FSS ...element with two C-shaped resonators at the top layer and a slotted circular patch at the bottom side, is proposed. The FSS element holds a size of 0.46λ × 0.46λ (at 28 GHz). A wideband Vivaldi antenna with an end-fire radiation is used to excite the elements of the FSS layers. The effects of different sizes, number, and the angular rotation of the FSS layers are employed to achieve the best antenna performance in terms of beam-tilting, realized gain, and reducing the sidelobe level (SLL). The best antenna performance is achieved when two unequal-sized FSS layers rotated to 45° and fixed under the Vivaldi. The proposed antenna is fabricated and measured. The obtained measured results show a maximum beam tilt angle of 38°, realized gain of 9 dBi, and SLL at -8 dB. The beam tilt angles are validated with the results obtained using the Snell's law in a multilayer environment and found a good agreement.
In this letter, a novel absorptive structure with a high-transmittance bandpass behavior is proposed based on the electromagnetically induced transparency-like effect. The desired response is ...achieved by employing cascaded lossy π-shaped and lossless dual-band reflective arrays. The lossy array consists of radiative and subradiant resonators. A resistor is loaded on the radiative resonator to consume the excited current within the stopband. The bright-dark mode coupling contributes to a transparency window with an insertion loss of 0.07 dB. By combining with the reflective array, two absorption bands are obtained at both sides of the passband, and the maximum absorptivity is above 98%. Meanwhile, the 10 dB reflection reduction behavior is realized within the operating band, and a good stealth performance is provided. The fabricated prototype is measured, and the simulation and experimental results are in a good agreement.
In this paper, a novel multiple input/multiple output (MIMO) antenna system with a graphene-based patch antenna array for THz communications channel capacity enhancement has been proposed and ...investigated. Systematic analysis has been conducted on the graphene load conductivity by determining the operating modes related to its chemical potential. Further, the projected MIMO antenna arrays have been designed with three different approaches such as homogeneous, photonic crystals, and optimized photonic crystals. The targeted MIMO antenna arrays have been compared with their radiation characteristics such as return loss, bandwidth, and gain. The obtained results in CST simulations of the proposed graphene-based 1×2 patch antenna array using the optimized photonic crystals substrate exhibited excellent performance improvements as compared to the homogeneous substrate and the photonic crystals substrate around 0.65 THz, which achieved a peak gain of 11.80 dB and broad bandwidth greater than 614 GHz. Next, The 2×2 MIMO system scenario was studied and analyzed using the mentioned targeted MIMO antenna arrays by calculating the total path loss and the channel capacity. The obtained results showed that the proposed 2×2 MIMO system with the MIMO antenna array based on the optimized photonic crystals substrate achieved the highest capacity and the lowest total loss compared to a simple MIMO antenna array based on a homogeneous substrate. The capacity was calculated as 23.64 bit/s/Hz, and this was a remarkable enhancement compared with previously reported studies. In addition, this capacity was investigated further for different system configurations and different spacings between the transmission and receiver antennas.
Recent advancements in communication systems require a high possible data rate and high gain to overcome the path losses. In this paper, a high gain novel microstrip patch antenna array design is ...proposed based on the photonic crystal in terahertz (THz), which can be employed for the next generation wireless communication technology and other interesting applications. The proposed antenna array is designed based on a thick silicon substrate having a high relative permittivity and embedded air cylinder holes, and then the radiation characteristics of this antenna array are compared to the one that is mounted on the homogeneous substrate. To validate the accuracy of the proposed antenna array, two different simulation techniques are used, CST Microwave Studio based on the finite integration technique and Ansys HFSS based on finite element technique which showed the convergence. For high radiation characteristics, the proposed antenna array resonated around 0.65 THz and showed remarkable enhancements. The projected design antenna array has obtained a minimal return loss of −53.66 dB, a larger bandwidth of 113.01 GHz and VSWR close to unity at a resonant frequency of 0.601 THz. The achieved gain and radiation efficiency were 11.60 dB and 86.75 %, respectively. Finally, the fabrication process to release the proposed antenna array structure is presented, furthermore, the link budget analysis is discussed by estimating the total loss.
Recent advancements in the next-generation wireless communication technologies require high gain and larger bandwidth. In this paper, a high gain novel 1 × 2 circular microstrip patch antenna array ...is proposed to operate around 0.65 THz based on different substrates. First, the proposed antenna array is designed based on air cylinders holes embedded in a thick polyimide substrate, and then by using air cuboids holes. The proposed antenna array model is compared with a homogeneous polyimide substrate. The simulation results showed that the performance of the proposed antenna array was enhanced especially by using air cuboids holes and achieved a minimal return loss of − 74.10 dB, a wide bandwidth greater than 290 GHz, a gain of 10.57 dB, and radiation efficiency of 82.96% at a resonance frequency of 0.65 THz. Next, the gain of the proposed antenna array is investigated further by using two different substrates with a modified non-periodic photonic crystal where the air cylinders holes and air cuboids holes are mixed at the same time and embedded in the substrate with different diameter values. The simulation showed an enhancement in the gain where the highest gain was achieved by antenna array 4 of 12.03 dB. The proposed antenna array can be useful in imaging, sensing, and next-generation wireless communication technologies. The simulation is carried out by using the CST Microwave Studio simulator.
