Maximum Transmission Coefficient Research Articles

Tunable conversion of electromagnetically induced transparency to electromagnetically induced absorption based on vanadium dioxide metastructure

Metastructure analogs of electromagnetically induced transparency (EIT) show great potential in telecommunications, light storage, and slow light, owing to the unremitting research of our predecessors. Research on electromagnetically induced absorption (EIA) has also been accelerating in recent years. However, few researchers have studied the switch between the EIT and EIA. This paper proposes a tunable conversion of EIT to EIA in the terahertz (THz) band, by employing vanadium dioxide (VO2), a phase change material. With the incidence of the electromagnetic wave, the split-ring resonator is coupled with a double U-shaped resonator when VO2 is set in the dielectric state, and destructive interference appears, resulting in EIT. The cross-shaped resonator works when VO2 functions in the metallic state, which allows coherence enhancement, and the EIA phenomenon can be observed. Moreover, the value of the maximum transmission coefficient reaches 0.837 at 0.570 THz with maximum group delay reaching up to 4.45 ps through calculation, proving the slow light effect of EIT. In the metallic state of VO2, the maximum absorption value arrives at 0.826 at 0.571 THz. The consistency of the simulation results is further confirmed by verifying the dual spring vibration model.

Bifunctional metasurface with ultra-broadband electromagnetically induced transparency and perfect transmissive polarization conversion

This paper proposes a metasurface that can simultaneously realize the dual functions of ultra-broadband electromagnetic induced transparency (EIT) and perfect transmission linear polarization conversion (LPC). The metasurface can be regarded as two identical layers separated by air, and each layer is composed of two N-type copper resonators rotated 45° counterclockwise immediately on both sides of the F4B dielectric layer. The simulation results show that the rotating N-type resonator causes the destructive interference of the electric resonance unit’s near-field coupling magnetic resonance unit, resulting in an ultra-wideband EIT effect with a maximum transmission coefficient of 0.93 and a relative bandwidth of 40.03%. It was also found that a near-perfect transmission LPC with a polarization conversion ratio of 99.97% was obtained near the 9.06 GHz frequency. The physical mechanisms of the EIT phenomenon and LPC are analyzed using the surface current distribution and magnetic field, and the frequency dependence of some structural parameters is also analyzed to illustrate the spectral properties of the depression. The metasurface was fabricated and measured to verify its bifunctional performance. This simultaneous implementation of EIT and LPC on the metasurface provides a new approach for applications in communications, multifunctional device design, and antennas.

Determination of the Acoustic Wave Velocity and Attenuation in Liquids with Different Acoustic Impedances Using an Acoustic Interferometer

Theoretical and experimental features of using an acoustic interferometer for determining the velocity and attenuation of an acoustic wave in liquids with different acoustic impedances are studied. It is shown for the first time that the indicated impedance determines the ratio of the resonance values of the maximum and minimum transmission coefficient S12 for the same transmitter–receiver pair on the dependence of the transmission coefficient on the distance between the transducers. A methodology has been developed for determining the wave attenuation of a liquid free from the influence of “apparent” attenuation associated with the loss of part of the acoustic power to the transducers.

Transient and recyclable organic microwave resonator using nanocellulose for 5G and Internet of Things applications

The rapid development of electronics has caused the accumulation of electronic waste that is threatening the environment and human health. The deployment of the Internet of Things (IoT), enabled by 5G microwave communication technology, will involve an increasing number of electronic devices. Microwave communication devices consist of petroleum/ceramic-based substrates and metallic traces that are non-biodegradable. Here, we report a smart, flexible, and transient organic microwave resonator (TOMR) using cellulose nanofibrils (CNF) nanopaper as substrate and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as conducting trace. The device produced a resonant profile with the maximum transmission coefficient (S21) amplitude of −14.95 dB at a resonant frequency of 2.75 GHz under ambient conditions (20 °C, 30% relative humidity (RH)). The TOMR demonstrated sensing capabilities, wherein increasing the %RH modulated the device’s resonant amplitude (-29 mdB/%RH from 0% to 50% RH and −90 mdB/%RH from 50% to 90% RH) and resonant frequency (3600 kHz/%RH). Moreover, the PEDOT:PSS trace could be reclaimed, recycled, and redeposited on a CNF nanopaper, which enabled the fabrication of a TOMR that displayed a similar resonant profile. Hence, this study demonstrates the first transient organic microwave resonator embedded with sensing capabilities and introduces a framework to minimize the environmental impact of 5G microwave communication devices for the IoT.

A Dual-Band Differential Intraoral Antenna and System for Wireless Data and Radiative Near-Field Power Transfer

Intraoral tongue drive system (iTDS) is a promising assistive technology for rehabilitating disabled persons. This article proposes a radiative near field power transfer (RNF-PT) system comprising an intraoral differential rectenna (rectifying antenna) and external power transmitter (RNF-Tx). A dual-band compact differential intraoral antenna operating in the Industrial, Scientific and Medical (ISM) band (2.45 GHz) and midfield band (1.9 GHz) is proposed for the data and power transmission modes, respectively. The proposed differential antenna and rectifier were designed and fabricated individually using a Rogers RT/duroid 6010 substrate. The differential rectifier shows a simulated conversion efficiency of 89.3% for a radio frequency (RF) input power of 14.78 dBm at 1.9 GHz with a 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula> load. The maximum transmission coefficient of −25.95 and −24.93 dB was achieved at a separation of 22 mm for the closed and opened mouth conditions, respectively. The measured impedance bandwidths of the proposed antenna in both the closed and open mouth of the test subject are around 10% in the midfield band and around 9.5% in the ISM band, respectively. The measured peak gain in the minced pork and saline solution was −20.48 dBic, −18.25 dBic at the frequency of 1.9 GHz and −18.54 dBi, and −16.88 dBi at the frequency of 2.45 GHz, respectively. The specific absorption rate (SAR) values have also been analyzed through simulations for both data and power transmission modes and are found acceptable in the closed and open mouth placements. Based on these acceptable SAR values, the link margin was theoretically calculated where it could communicate over a reasonable distance. Thus, the proposed intraoral differential antenna with a rectifier is ideal for data and PT support in iTDS-based applications.

Influence of local deformation on valley transport properties in the line defect of graphene

The line defect of graphene has significant applications in valleytronics, which has received extensive attention in recent years. It is found experimentally that there exists local deformation around the line defect. Current studies generally believe that the influence of local deformation on the valley transport properties can be negligible, because the modifications to the nearest neighbour hopping energy is less than 5% under the small deformation. Based on the first-principles calculations and the non-equilibrium Green’s function method, we investigated the effect of local deformation on the valley transport properties of two different kinds of line defects, the 58 ring line defect and the 57 ring line defect. It is found that for the 58 ring line defect, the effect of local deformation on the valley transmission coefficient is not evident at lower energies. However, at higher energies, the impact of local deformation is obvious, and the maximum valley transmission coefficient does not decrease with increasing energy, but can be maintained 1 within a large energy range. In contrast, the influence of local deformation on the valley transmission coefficient of the 57 ring line defect indeed can be negligible, regardless of the level of energy. Further investigation indicates that the change of the C—C bond length connected to the two defect atoms in the 58 ring plays a key role in the transmission of the valley states across the line defect. If this part of the influence is not taken into account, the valley transmission coefficient is nearly unaffected by the local deformation. The valley state enters the right side of the line defect directly through the bond connected to the line defect, so the change in bond length connected to the line defect has a significant impact on the valley transmission. This special structure does not exist in the 57 ring, where the valley states will have to pass through a narrow region containing 57 ring to enter the right side of the line defect, resulting in different valley scattering phenomena. By constructing two parallel line defects, the 100% valley polarization can be achieved in a large angular range with the 58 ring line defect. The finding has important implications for the design of graphene line defect based valley filters.

Three-layer model with absorption for conservative estimation of the maximum acoustic transmission coefficient through the human skull for transcranial ultrasound stimulation

Transcranial ultrasound stimulation (TUS) has been shown to be a safe and effective technique for non-invasive superficial and deep brain stimulation. Safe and efficient translation to humans requires estimating the acoustic attenuation of the human skull. Nevertheless, there are no international guidelines for estimating the impact of the skull bone. A tissue independent, arbitrary derating was developed by the U.S. Food and Drug Administration to take into account tissue absorption (0.3 dB/cm-MHz) for diagnostic ultrasound. However, for the case of transcranial ultrasound imaging, the FDA model does not take into account the insertion loss induced by the skull bone, nor the absorption by brain tissue. Therefore, the estimated absorption is overly conservative which could potentially limit TUS applications if the same guidelines were to be adopted. Here we propose a three-layer model including bone absorption to calculate the maximum pressure transmission through the human skull for frequencies ranging between 100 kHz and 1.5 MHz. The calculated pressure transmission decreases with the frequency and the thickness of the bone, with peaks for each thickness corresponding to a multiple of half the wavelength. The 95th percentile maximum transmission was calculated over the accessible surface of 20 human skulls for 12 typical diameters of the ultrasound beam on the skull surface, and varies between 40% and 78%. To facilitate the safe adjustment of the acoustic pressure for short ultrasound pulses, such as transcranial imaging or transcranial ultrasound stimulation, a table summarizes the maximum pressure transmission for each ultrasound beam diameter and each frequency.

A compact radio frequency identification tag antenna with loaded coupling rings for two‐side anti‐metal design

A compact ultra-high frequency radio frequency identification tag antenna loaded with a pair of rectangular coupling rings for two-side anti-metal performance is proposed. It evolves from a planar inverted-F antenna and has the same upper and lower structures. A pair of coupling rings is symmetrically loaded on the inner sides of the upper and lower substrates, and the tag's maximum power transmission coefficient can be achieved when either side of the antenna is placed on a metallic plate. The proposed tag antenna maintains a compact size of 34 mm × 28 mm × 5 mm. The measured results show that it has the lowest sensitivity of −14.8 dBm when the lower side is on a metallic plate and the lowest sensitivity of −14.2 dBm when the upper side is on a metallic plate. The proposed tag antenna is featured in a compact size, low sensitivities, and anti-metal performance on two sides. It may be used in the areas such as the industrial internet of things.

Investigation of optical phenomena in multispectral matrix photodetector based on silicon

A study is presented in the field of development and creation of modernized multi-layer color separation multispectral systems with increased color resolution. The types of structures of the developed patterns of matrix photodetectors based on multilayer silicon with working layers for use in the blue, green, red and infrared spectral ranges are considered. A method for calculating silicon layers in the form of optical films with specified characteristics is proposed. The silicon layers act as both a sensing element and a specific wavelength filter to highlight the blue, green, red and infrared ranges of the spectrum. The reflection and transmission coefficients were calculated for the selected wavelengths at various angles of incidence on the sensor. The Brewster angle for these wavelengths is also calculated. The possible presence of a microlens sensor surface is taken into account. Calculations are presented for cells with four-layer and two-layer structures for various combinations of layers. The dependences of the reflection and transmission coefficients for two-layer and four-layer structures of semiconductor sensors for p- and s-polarization, also for unpolarized light, are obtained. It is shown that the combination of layers in the red and infrared ranges of the spectra has the minimum reflection coefficient and the maximum transmission coefficient. The results obtained can be used in the development of multilayer multispectral systems with registration of infrared radiation. As a result, it is possible to use a pair of red and infrared spectra as the basis of a matrix photodetector pattern, and layers of blue and green spectra as auxiliary ones for building a full-color image.

Fabrication of a highly efficient multilayer microwaves insulator based on CuFe2O4/(Pb1−xLax)/(Zr1−yTiy)O3 (composite: 7/60/40) (0 ≤ x, y ≤ 1) and Cu-doped g-C3N4 nanograins

Nowadays, microwave pollution is a major concern around the world. Therefore, the construction of multilayer microwave absorbers with low thickness and wide bandwidth has been investigated. A novel multilayer broadband microwave insulator with high performance containing fillers comprised of copper ferrite spinel (CuFe2O4) nanograins (NGs), lead zirconium titanate ceramic (Pb1−xLax)(Zr1−yTiy)O3 (composite: 7/60/40) (0≤x,y ≤ 1) (PLZT) nanoparticles (NPs), and copper-doped carbon nitride graphitic (Cu-doped g-C3N4) nanosheets (NS) based on epoxy resin has been successfully prepared. The crystal structure and morphology of synthesized nanograins were specified using XRD, SEM, and EDX/mapping analysis. In addition, the microwave absorption properties of the resulting multilayer microwave insulator were evaluated using a vector network analyzer (VSM) in the frequency range of 8–12 GHz. Response surface methodology (RSM) was applied to the design of experiments to reduce the experimental time and cost, and obtain the optimal conditions. The weight percentage (wt.%) of CuFe2O4 magnetic nanograins, (Pb1−xLax)(Zr1−yTiy)O3 (0 ≤ x,y ≤ 1) dielectric NGs, Cu-doped g-C3N4 electric conductivity nanosheets, and thickness of the designed insulators were optimized using the RSM method to attain a multilayer microwave insulator with the optimal microwaves absorption efficiency. The minimum reflection loss (maximum absorption efficiency) was determined to be < –30 dB (absorption >99.9%) for the optimized multilayer microwaves insulator under the conditions of 3.0 wt% CuFe2O4 magnetic nanoparticles, 5 wt% (Pb1−xLax)(Zr1−yTiy)O3 (0≤x,y ≤ 1) dielectric NGs, 1.0 wt% Cu-doped g-C3N4 electric conductive nanosheets with 1 mm thickness in the microwave frequency range of 8–12 GHz (X-band). The highest attenuation coefficient (>500 dB/m) showed that the microwaves energy was weakened. In addition, the minimum reflection coefficient (maximum transmission coefficient) was calculated to be ∼0.01 (RL = −35 dB, AL = 99.99%). Finally, the obtained results show that these factors and their levels were correctly selected for the fabrication of high-performance multilayer microwave insulators.

Achieving polarization control by utilizing electromagnetically induced transparency based on metasurface

In this study, a design of transmissive linear-to-circular polarization conversion (LCPC) related to electromagnetically induced transparency (EIT) by arranging four sets of asymmetric resonators on a metasurface in a cross-shaped distribution is theoretically reported in the terahertz (THz) regime. It has numerically demonstrated that the bright modes and quasi-dark modes can also be mutually coupled when the x-polarized (TM) and y-polarized (TE) waves are incidents, resulting in a famous EIT phenomenon. Subsequently, when the direction of the electric fields of the electromagnetic (EM) waves are incident along the x-axis with an angle of 45°, the electric fields can be decomposed into the x- and y-directions. At this time, the corresponding amplitude and phase meet the conditions of the LCPC. Furthermore, for the TM and TE waves, the values of the maximum transmission coefficients respectively reach up to 0.910 at 1.384 THz and 0.890 at 1.277 THz. Correspondingly, two brand-new bright transparent windows are located in 1.276-1.454 THz for the TM waves and 1.206-1.373 THz for the TE waves. Concurrently, the band of the maximum 3 dB axial ratio is obtained from 1.308 THz to 1.343 THz with a relative bandwidth of 3%.

A compact four-peak MIM filter based on asymmetric distribution of resonators

We theoretically propose and numerically analyze a compact Metal-Insulator-Metal(MIM) filter based on an asymmetric structure which can produce four peaks in the spectrum. The filter can generate four transmission peaks while the maximum transmission coefficient of each peak is above 90%, and each transmission peak can be individually tuned by changing the coupling angle between the resonators and the waveguide. The structure consists of a pair of asymmetric cavities above and below the waveguide. By adjusting the coupling angle between the cavities and waveguide, each cavity can filter out light of a specific wavelength. The transmittance of the lowest transmission peak could be 3% and each transmission peak has a narrow frequency width. The quality factor (Q) of the resonances are 29.5, 42.9, 17.3 and 77.1, respectively. The sensitivities are 500nm/RIU, 588 nm/RIU, 659 nm/RIU and 827 nm/RIU. The FOMs are 26.3, 39.2, 15.3, 75.2. Multimode interference coupled-mode theory (MICMT) is used for numerical calculation and theoretical analysis. The structure is compact and easy to be fabricated and has potential applications in nano-optical communication.

Evaluation of Magnetic Properties of Ceramic Coated Soft Magnetic Composite and its Simulation for Microwave Devices

High frequency applications (in GHz) require soft magnetic materials with high resistivity, anisotropy and low losses above the ferromagnetic resonance. In this research work, fabrication of toroid cores of the magnesium compound coated soft magnetic composites (M-SMC) was carried out. High frequency magnetic properties (0.5–8 GHz) and microwave complex properties of the materials were determined using B-H analyzer and vector network analyzer. The reflection and transmission coefficients were calculated using the scattering parameters. Using Nicolson-Ross-Weir algorithm complex permeability and complex permittivity were calculated. Mathematical model for hysteresis based on Preisach Classical Model for hysteresis was developed to simulate the hysteresis of the material. By doing variation in thickness of the sample, a broad range of frequency spanning from 0.5 GHz to 7.5 GHz is covered. The optimum range for reflection coefficient i.e. 0.6–0.9 is in the frequency range of 3–5.5 GHz for samples of thickness in the ranges of 2–4 mm and 6–8 mm. The maximum transmission coefficient obtained was 0.6 in the frequency range of 0.5–1.5 GHz for samples of various thickness ranges viz. 2–5.5 mm and 6.5 to 8 mm. The transmission coefficient of 0.6 was also obtained in high frequency range of 3–5.5 GHz in case of samples of thickness 4–6 mm and above 7 GHz for samples of thickness above 6 mm.

Theoretical proposal of electromagnetically induced transparency with a transmissive polarization conversion based on metamaterials

The polarization of electromagnetic waves is a key feature in the research areas of modern optics and information science. How to efficiently convert the polarization directions of the EM waves remains to be a challenge in electromagnetically induced transparency (EIT). Here, we theoretically propose a double-layer metamaterial with four symmetric H-shaped resonators, which can achieve the EIT phenomenon and transmissive linear polarization conversion (LPC). The EIT effect is acquired depending on the destructive interference between the electric and magnetic resonances. It is demonstrated that electromagnetic coupling is realized by reducing the structural symmetry of the rotated H-shaped resonators. Furthermore, the value of the maximum transmission coefficient reaches up to 0.900 at 14.202 GHz. The values of the transmission dips are 0.094 at 9.913 GHz and 0.176 at 16.101 GHz, respectively. Moreover, a broad transparency window that is higher than 0.8 can be gained spanning from 11.913 GHz to 15.289 GHz, and the relative bandwidth is 24.8%. Meanwhile, the momentous capability of the LPC is also observed. The transmissive cross-polarization conversion is well observed at 9.913 GHz and 16.101 GHz, where the polarization conversion ratios respectively are 90.2% and 91.8%. In the transparent window, a slow-light effect is highlighted. The values of the maximum group delay and group index respectively approach 91 ns and 1925. The FDTD simulation had been employed to further verify the effectiveness of group delay. In particular, the surface current distributions of the H-shaped resonators are employed to explain the mechanisms of the EIT effect and the transmissive LPC. Surpassing the general EIT structures and polarization converters, the proposed metamaterial is synchronously equipped with the EIT behavior and LPC by one same structure, which has numerous potential applications in communication and antenna technologies.

Reflection and transmission of electromagnetic pulses at a planar dielectric interface: Theory and quantum lattice simulations

There is considerable interest in the application of quantum information science to advance computations in plasma physics. A particular point of curiosity is whether it is possible to take advantage of quantum computers to speed up numerical simulations relative to conventional computers. Many of the topics in fusion plasma physics are classical in nature. In order to implement them on quantum computers, it will require couching a classical problem in the language of quantum mechanics. Electromagnetic waves are routinely used in fusion experiments to heat a plasma or to generate currents in the plasma. The propagation of electromagnetic waves is described by Maxwell equations with an appropriate description of the plasma as a dielectric medium. Before advancing to the tensor dielectric of a magnetized plasma, this paper considers electromagnetic wave propagation in a one-dimensional inhomogeneous scalar dielectric. The classic theory of scattering of plane electromagnetic waves at a planar interface, separating two different dielectric media, leads to Fresnel equations for reflection and transmission coefficients. In contrast to plane waves, this paper is on the reflection and transmission of a spatially confined electromagnetic pulse. Following an analytical formulation for the scattering of a Gaussian pulse, it is deduced that the maximum transmission coefficient for a pulse is n2/n1 times that for a plane wave; the incident and transmitted pulses propagate in dielectric media with refractive indices n1 and n2, respectively. The analytical theory is complemented by numerical simulations using a quantum lattice algorithm for Maxwell equations. The algorithm, based on the Riemann–Silberstein–Weber representation of the electromagnetic fields and expressed in terms of qubits, is an interleaved sequence of entangling operators at each lattice site and unitary streaming operators, which transmit information from one site to an adjacent lattice site. Besides substantiating results from the theory for Gaussian pulses, numerical simulations show their validity for non-Gaussian pulses. Apart from their time-asymptotic forms, the simulations display an interplay between the incident, reflected, and transmitted pulses in the vicinity of the transition region between two dielectric media.

Сверхширокополосный полосно-пропускающий фильтр на основе многослойного полосково-щелевого перехода.

The paper presents the results of theoretical and experimental researches of an ultra-wideband bandpass filter (UWB BPF) based on a multilayer strip-slot transition. Theoretical results are obtained in two ways: 1) by designing an equivalent circuit of the UWB BPF where each element is presented in the form of a two-port network with the corresponding matrix of A-parameters and 2) by numerical simulation in a rigorous formulation of the electrodynamics problem. Experimental results were obtained on a sample of the UWB BPF using a vector network analyzer. The results of theoretical and experimental researches are in good qualitative and numerical agreement. The investigated UWB BPF has a relative pass band at a level of -3 dB relative to the maximum transmission coefficient equal to 49,2% according to experimental research and 51% according to theoretical research.

Electrically tunable terahertz switch based on superconducting subwavelength hole arrays.

We experimentally demonstrate an electrically tunable superconducting device capable of switching the extraordinary terahertz (THz) transmission. The planar device consists of subwavelength hole arrays with real-time control capability. The maximum transmission coefficient at 0.33 THz is 0.98 and decreases to 0.17 when the applied voltage only increases to 1.3 V. A relative intensity modulation of 82.7% is observed, making this device an efficient THz switch. Additionally, this device exhibits good narrow-bandpass characteristics within 2 THz, which can be used as a frequency-selective component. This study offers an ideal tuning method and delivers a promising approach for designing active and miniaturized devices in THz cryogenic systems.

Transmittance on combinatorial structures of triple potential barriers

Semiconductor materials used as potential barriers in the study are GaAs, GaSb, and AlAs. These materials will be arranged in certain combinations to form triple potential barrier structures and the effect of combinations will be analysed against transmission coefficient values. In this study, the maximum energy of the electron is 1 eV and the matrix propagation method is used where the effect of the combinations structure on transmission coefficient values is numerically analysed using a computational program. The results showed that the structuring potential barrier affects the value of the transmission coefficient. In the uniform barriers arrangements, the value of the transmission coefficient decreases with increasing potential barrier energy. Whereas in the arrangement of different barrier combinations, two opposing combination arrangements have the same transmission coefficient values. Thus, from six combination arrangements, there are three kinds of transmission coefficient values. The maximum transmission coefficient value is 1.000 in the triple potential barrier of GaSb at 0.49 eV. Research on the tunnel effect contributed to the development of electronic and optoelectronic devices such as transistors and lasers.

The Analysis of Light Intensity Transmission Coefficient Through Plastic Fibers for the Design of Closed Room Lighting without Electricity

The phenomenon of total internal reflection can be used to guide the light to be transmitted from one place to another, it is applied to the guiding principle of light in fiber optics. A fiber rope made of clear plastic material with a uniform refractive index, when one end fired a beam of light then the light will be forwarded along the strap so that out at the other end. This principle can be applied as a lighting source in a closed room by passing light from the outdoors by using plastic fiber, so it doesn’t need the electricity. In this study, theoretical analysis of the percentage of the intensity of light transmitted by the fiber plastic succeed as a function of the refractive index and determine the transmission coefficient for some plastic seeds are eligible to be used as a plastic fiber light successor. From the results of deriving the equation, the light transmission coefficient of plastic is and the terms of plastic seeds that can be used as a plastic fiber are having a refractive index . Based on refractive index data from profesionalplastics, the maximum transmission coefficient value for Ethylene Tetrafluoro Ethylene Copolymer is 82.23% and the minimum transmission value of Fluorinated Ethylene Propylene Copolymer is 55.99%.

TRANSMISSION COEFFICIENT OF POWER DENSITY INTO SKIN TISSUE BETWEEN 6 AND 300 GHZ.

The latest electromagnetic safety guidelines define transmitted or epithelial power density as the basic restriction above 6GHz. In this note, we derive an approximation for a conservative transmission coefficient for quasi plane wave incidence as a function of the frequency for the normal component of the Poynting vector with respect to the evaluation plane or tissue surface |Sz inc| and for its modulus ||Sinc||. The maximum transmission coefficient for the normal component of the Poynting vector ${\boldsymbol{T}}_{\mathbf{z}}^{\mathbf{max}}$ is 1 independent of tissue composition and frequency. Approximations of ${\boldsymbol{T}}_{\mathbf{total}}^{\mathbf{max}}$ normalized to ||Sinc|| for thin and thick stratum corneum are provided allowing higher exposures. These approximations allow to conservatively demonstrate compliance with basic restrictions when quasi plane-wave conditions are locally satisfied and enhancement effects of standing waves between source and body can be neglected. The reported results are important to regulators and standardization bodies regarding revisions of compliance requirements and safety guidelines.