Investigation into Low SAR PIFA Antenna and Design a Very Low SAR U-slot Antenna using Frequency Selective Surface for cell-phones and Wearable Applications

There are very important questions. “Do Electromagnetic waves have irreparable effects on human or not?” “Are there any relation between cancer and waves?” and finally “what should we do to be safe?”. In the present article, these questions will be answered simply and professionally. First of all, Specific Absorption rate (SAR) is define then L-Slot and U-slot antenna is designed and simulated using cell-phones and wearable applications, operating at  and  consist of GSM900 and GSM1800. Standard frequency band width for the first and second band is  and  for uplink and downlink and in the present research these numbers are obtained. The SAR of each antenna is measured and is compared with each other. Thanks to design of antenna, The SAR of U-Slot antenna is very low and it is almost stimulated  and this sentence means this antenna is anti-cancer. Finally, Some SRR unit-cells are designed and when they are used in structure, SAR will be more decrease. Last SAR value is  and  for each bands .In the last table, There are some comparison between different creditable references and present article SAR reduction is acceptable and it is near to  percentage

Study of hybrid and pure plasmonic terahertz antennas based on graphene guided-wave structures

Graphene is a unique material for the implementation of terahertz antennas due to extraordinary properties of the resulting devices, such as tunability and compactness. Existing graphene antennas are based on pure plasmonic structures, which are compact but show moderate to high losses. To achieve higher efficiency with low cost, one can apply the theory behind dielectric resonator antennas widely used in millimeter-wave systems. This paper presents the concept of hybridization of surface plasmon and dielectric wave modes. Then, via an analysis of one-dimensional structures, a comparison of the potential capabilities of pure and hybrid plasmonic antennas is performed from the perspectives of radiation efficiency, tunability, and miniaturization. Additionally, the impact of the quality of graphene upon the performance of the compared structures is evaluated. On the one hand, results show that hybrid structures deliver high gain with moderate miniaturization and tunability, rendering them suitable for applications requiring a delicate balance between the three aspects. On the other hand, pure plasmonic structures can provide higher miniaturization and tunability, yet with low efficiency, suggesting their use for application domains with high flexibility requirements or stringent physical constraints.Author's final draf

Dispersion curve engineering for automated topology design of a unit cell in spoof surface plasmon polaritons

Abstract In this paper, an automatic design method is proposed for unit cell in spoof surface plasmon polaritons (SSPP) with an almost arbitrary dispersion curve. In this method, the pixel configuration is considered for the unit cell and, by using the binary particle swarm optimization method, the proper topology of the unit cell is explored so as to reach the target dispersion curve. Unlike the traditional method of controlling the dispersion curve, which is performed based on changing the geometric parameters of the predetermined unit cell, in this method, there is no need to know the shape of the unit cell, and the dispersion curve of the modes of SSPP unit cell can be controlled independently with more freedom. Two unit cell samples are designed in order to show the efficiency of the procedure. In the first sample, the dispersion curve is designed to have the lowest asymptotic frequency; in the second sample, the dispersion curve of the second mode is controlled independently from the first mode and is changed arbitrarily. SSPP transmission lines which are related to the unit cells of the two samples are designed, and it is demonstrated that measurement and simulation results are greatly in line with each other

A two-dimensional grating surface made of quaternary Huygens elements excited by a real source

Abstract In this article, a new method to create an anomalous reflection in the desired direction is proposed. Two-dimensional grating surfaces consisting of four particles with the properties of a Huygens source are employed in each period. Then, this method is extended to the problem in which the grating surface is illuminated by a real source such as a horn. In this case, the designed grating surface has different periods in both directions to collimate the reflected wave and give an in-phase wavefront. Using our method, a high-efficiency reflectarray (RA) based on quaternary Huygens grating is designed. This RA is distinguished from common RAs due to its beam squint capability. This array offers more aperture efficiency and thus more gain in comparison to the leaky waves that inherently have low aperture efficiency. Therefore, our designed RA can compete with leaky wave antennas in many applications. The mentioned RA is designed to have the main beam in the direction of $$\left( {{\theta _0} = {{68}^{\circ }},{\varphi _0} = {{225}^{\circ }}} \right)$$ θ 0 = 68 ∘ , φ 0 = 225 ∘ , at the frequency of 12 GHz. The simulation results show the realized gain and SLL of this antenna are 24.8 dB and $$-15.5$$ - 15.5  dB, respectively. Also, by changing the frequency in the range of 12–15 GHz, the direction of the main beam varies from $$\left( {{{68}^{\circ }}, {{225}^{\circ }}} \right)$$ 68 ∘ , 225 ∘ to $$\left( {{{39}^{\circ }}, {{225}^{\circ }}} \right)$$ 39 ∘ , 225 ∘

ANALYTICAL METHOD FOR DESIGNING FSS-BACKED REFLECTARRAY ANTENNA USING TRANSMISSION LINE APPROACH

Abstract The main purpose of this paper is introducing a new method based on the transmission line approach for designing FSS-backed reflecarray antennas. For this reason a dual band reflectarray antenna is designed. This antenna contains a conventional single layer RA and a FSS backed double layer RA with 54% and 50% efficiency operating at X band and K band, respectively. A double layer FSS is used between RAs to isolate them. K band cell element is designed and analyzed using transmission line method and consideration of equivalent circuit for elements of each layer. Then the results obtained using this technique is compared to those found by CST and ADS. The comparison shows a good agreement. Jerusalem cross dipole with variable size is employed as radiation element in both bands. The most important properties of our suggested array are low cross polarization and high efficiency

Dual-band X/Ku Reflectarray Antenna Using a Novel FSS-Backed Unit-Cell with Quasi-Spiral Phase Delay Line

Abstract A novel FSS-Backed reflectarray unit cell is introduced to design a dual-band X/Ku Reflectarray Antenna (RA). A Ku-band RA based on this FSS-Backed cell element is designed and located on the top of a conventional X-band RA. Actually, the band-stop Frequency Selective Surface (FSS) property is applied to a wideband element to create isolation between X and Ku band RAs which utilizing the same radiating element. A wideband cell element with attached quasi-spiral phase delay line is employed for phase compensation in both bands. As a FSS-backed cell element, the remarkable feature of the proposed dual band unit cell compared to previous works is its possibility of operation in closer frequency bands in comparison with other dual band FSS-backed RAs. Two reflectarrays with aperture size of 7.65λ×7.65λ and 7.35λ×7.35λ are designed, fabricated and measured for X band and Ku band, respectively. Measured results show 1-dB gain bandwidth of 12% for X band and 11% for Ku band which demonstrate wideband operation of this dual-band reflectarray antenna

Surveying of pure and hybrid plasmonic structures based on graphene for Terahertz Antenna

Graphene is a unique material for the implementation of terahertz antennas due to extraordinary properties of the resulting devices, such as tunability and compactness. Existing graphene antennas are based on pure plasmonic structures, which are compact but show moderate to high losses. To achieve higher efficiency with low cost, one can apply the theory behind dielectric resonator antennas widely used in millimeter-wave systems. This paper presents the concept of hybridization of surface plasmon and dielectric wave modes. Radiation efficiency, reconfigurability, and miniaturization of antennas built upon this principle are qualitatively discussed and compared with those of pure plasmonic antennas. To this end, a quantitative study of pure and hybrid plas-monic one-dimensional guided-wave structures is performed. The results show that hybrid structures can be employed to design terahertz antennas with high radiation efficiency and gain, moderate miniaturization, and tunability, while terahertz antennas based on pure plasmonic structures can provide high miniaturization and tunability yet with low radiation efficiency and gain.Peer ReviewedPostprint (published version

Surveying of pure and hybrid plasmonic structures based on graphene for Terahertz Antenna

Graphene is a unique material for the implementation of terahertz antennas due to extraordinary properties of the resulting devices, such as tunability and compactness. Existing graphene antennas are based on pure plasmonic structures, which are compact but show moderate to high losses. To achieve higher efficiency with low cost, one can apply the theory behind dielectric resonator antennas widely used in millimeter-wave systems. This paper presents the concept of hybridization of surface plasmon and dielectric wave modes. Radiation efficiency, reconfigurability, and miniaturization of antennas built upon this principle are qualitatively discussed and compared with those of pure plasmonic antennas. To this end, a quantitative study of pure and hybrid plas-monic one-dimensional guided-wave structures is performed. The results show that hybrid structures can be employed to design terahertz antennas with high radiation efficiency and gain, moderate miniaturization, and tunability, while terahertz antennas based on pure plasmonic structures can provide high miniaturization and tunability yet with low radiation efficiency and gain.Peer Reviewe

Study of hybrid and pure plasmonic terahertz antennas based on graphene guided-wave structures

Graphene is a unique material for the implementation of terahertz antennas due to extraordinary properties of the resulting devices, such as tunability and compactness. Existing graphene antennas are based on pure plasmonic structures, which are compact but show moderate to high losses. To achieve higher efficiency with low cost, one can apply the theory behind dielectric resonator antennas widely used in millimeter-wave systems. This paper presents the concept of hybridization of surface plasmon and dielectric wave modes. Then, via an analysis of one-dimensional structures, a comparison of the potential capabilities of pure and hybrid plasmonic antennas is performed from the perspectives of radiation efficiency, tunability, and miniaturization. Additionally, the impact of the quality of graphene upon the performance of the compared structures is evaluated. On the one hand, results show that hybrid structures deliver high gain with moderate miniaturization and tunability, rendering them suitable for applications requiring a delicate balance between the three aspects. On the other hand, pure plasmonic structures can provide higher miniaturization and tunability, yet with low efficiency, suggesting their use for application domains with high flexibility requirements or stringent physical constraints