EM Wave Propagation Research Articles

Use and Accuracy of Numerical Weather Predictions to Support EM Wave Propagation Experiments

In order to keep up with the demand for new services, future satellite-to-ground communications will operate at higher frequencies, notably in the 20–50 GHz bands. Consequently, new challenges arise for system designers as the attenuation of the signal crossing the troposphere increases with frequency. Propagation experiments, such as the on-going Alphasat campaign, provide direct measurements of the attenuation. However, other data sources, such as collocated radiometers, are needed to recover the attenuation in nonrainy conditions. This paper uses the Weather Research and Forecasting (WRF) software and investigates Numerical Weather Prediction (NWP) models as an alternative source of nonrainy attenuation time series. Four months of measured Alphasat and radiometric signals collected at Spino d’Adda serve as the reference to assess the accuracy of NWP-derived attenuation. The best agreement between the NWP-derived and the radiometric nonrainy attenuations is achieved with the Tiedtke cumulus scheme. Considering the limits in accuracy inherent to the propagation and radiometric data, the resulting total attenuation statistics are acceptable. The results are expected to improve further with NWP simulation domains closer to the state of the art.

Study of symmetric and asymmetric defect positions in a photonic crystal supercell

A 2D supercell photonic crystal consisting of dielectric cylindrical rods in air medium was used to study the effect of symmetry of the defects on the resonance modes. A single defect was introduced at every possible position in the crystal and the transmission properties were studied. When a defect is introduced on an axis which passes through the centre of the crystal and is perpendicular to the direction of propagation of EM wave, the mirror symmetry along an axis passing through the centre of the supercell (Soy axis) is preserved. When a defect is introduced on an axis that passes through the centre of the crystal and is parallel to the direction of propagation of EM wave, the mirror symmetry along the axis Sox passing through the centre of the supercell is preserved but the mirror symmetry along Soy is broken. However, when the defect is placed at the centre of the crystal, the mirror symmetries is preserved along both the axes defined in the supercell. It is seen that TM mode needs to see mirror symmetry in the direction of propagation within the supercell, (mirror symmetry of defects with respect to Soyaxis) in order to produce a strong resonance peak. However the presence of mirror symmetry along Sox seems to have little to no effect on the resonance peak. The single defects placed on the E∥ and E⊥ axes passing through the centre of the crystal and their respective supercell defect modes have been discussed in this paper.

Design of miniaturised meandered loop on‐chip antenna with enhanced gain using shorted partially shield layer for communication at 9.45 GHz

A significantly miniaturised meandered loop on-chip antenna (MeLOCA) for communication at 9.45 GHz has been proposed. First, a meandered loop antenna size is reduced and its gain is enhanced by introducing a partially shield layer (PSL). Then, the antenna size is further reduced with a shorted conical pin connecting the antenna and PSL. The PSL provides capacitive loading and shifts resonating frequency of the reference antenna from 23 to 11.07 GHz. Also, it reduces substrate loss by obstructing EM wave propagation towards the lossy Silicon substrate and offers gain enhancement. Moreover, shorting to PSL offers an enhanced electrical length and shifts resonating frequency at 9.45 GHz. Thus, combination of PSL and shorting pin leads to realise the optimally designed MeLOCA size of 2.1 × 2 mm2 with reduction up to λ 0/15.11. Simulated maximum gain and efficiency of −29 dB and 21.07%, respectively, make the antenna a suitable candidate for short range communication. Also, maximum of 16 and 20 dB and minimum of 3 and 5.6 dB isolations between co-polarisation and cross-polarisation components are achieved, respectively, in E and H planes. A prototype has been fabricated using 0.18 μm CMOS technology and good agreement between simulated and measured return loss characteristics is observed.

Simulation of subsurface imaging for remote sensing and buried object detection from airborne platforms

ABSTRACT This paper addresses the problem of efficient simulations of the signal backscattered from buried structures. The proposed modelling of subsurface soil structure is based on a geologically – and hydrologically-motivated approach by using of real geological database. Six different Soil Typological Units have been used to model the inhomogeneous and geological soil structures as well as for moisture profile simulation. We use the semi-empirical pedotransfer function to calculate the Complex Relative Effective Permittivity in frequency range of 0.3–1.3 GHz. The subsurface penetration capabilities have been analysed with the regard to attenuation along the propagation path in a layered structure. We use the backward-propagation matrix and ray-tracing method to compute the backscattered signals from five targets located at five different depths in order to analyse the defocusing effects due to EM wave propagation. The computation was performed for three different radar systems with various bandwidths and carrier frequencies.

Planar 0.05–1.1 THz Laminate-Based Transition Designs for Integrating High-Frequency Photodiodes With Rectangular Waveguides

Compact planar laminate-based transitions for integrating high-frequency photodiodes (PDs) with rectangular waveguides (WRs) are presented for the WR15 to WR1 standard waveguide bands, i.e., from 0.05 THz up to 1.1 THz. The transitions couple the optically generated (e.g., via heterodyning) millimeter-wave or terahertz signals from the grounded coplanar waveguide (GCPW) output of the PD chip to the WR. To our knowledge, this is the first scalable integration concept that enables hermetic photodiode packaging up to the terahertz frequency range. For the WR15-WR6 bands, all transitions are designed on ultrathin microfiber reinforced PTFE composites (127-μm Rogers RT/duroid 5880 laminate). For the WR5-WR2.2 and the WR1.5-WR1 bands, liquid crystalline polymer ULTRALAM 3850 laminates are used with a thickness of 50 and 25 μm, respectively. The proposed GCPW-WR transition design is based on a double-slot antenna structure and enables the development of fully hermetic photonic packages, which is required to improve the durability of the PD chip. The transition designs are optimized by systematic EM-wave propagation modeling for achieving a wide operational bandwidth of up to 30% of the respective center frequency for each WR band. The optimized transitions exhibit an average insertion loss of about 1.5 dB and a return loss of about 10 dB for all waveguide bands (WR15-WR1). Based upon the systematic numerical modeling, generic guidelines are developed that allow designing a specific transition for any given waveguide band to 1.1 THz. In addition to the numerical analysis, GCPW-WR12 transitions for E-band (60-90 GHz) operation are fabricated and integrated with InP-based balanced-PD chips and GaAs HEMT MMIC medium power amplifiers in a fully hermetic package. Furthermore, hermetic WR12 coherent photonic mixer (CPX) modules are developed. The packaged WR12-type CPX allows direct optical-to-wireless conversion of optical baseband or IF-band signals, e.g., for radio-over-fiber fronthauling in mobile communications. The WR12-CPX module provides RF output power of up to +15 dB·m at 77.5 GHz.

Realistic Expectations for Deep Ground Penetrating Radar Performance

Ground penetrating radar (GPR) is unique amongst geophysical tools in terms of its imaging resolution and the diversity of its applications. Since its commercialisation four decades ago, GPR has also been distinguished because of the prevalence of some of its purveyors to oversell the method’s capabilities, relying largely on the end users’ lack of understanding of the underlying physics. Early adopters in the 1980s and 90s were dismayed to find that environments suitable for its purported ubiquitous deep penetration capabilities were rare and that it required resistivities well into the 1000s of Ohm m. Regardless of the advances made in electronics and antenna design in the intervening decades, the fundamental limitations have not changed.Misconceptions, “specsmanship” and hype have continued to abound in the GPR marketplace, particularly in recent years. Systems purporting to penetrate hundreds of metres using “megawatt” transmitters from the former Eastern Bloc have been promoted for mineral exploration, particularly in Australia and Africa. Other pseudo-radar concepts, such as the use of beam forming to achieve kilometres of penetration with centimetre accuracy, or THz laser scanners which can detect individual diamonds deep underground, have generally targeted junior exploration groups who lack in-house geophysical guidance.This work provides an overview of the fundamentals of non-dispersive EM wave propagation in the ground and an examination of the recent published performance claims of some GPR and pseudo-GPR systems within the context of accepted EM theory. The accepted methods for potentially increasing GPR performance, given the emerging technologies such as novel transmitter and receiver designs and new GPR antennas, are also discussed.

Enhancement of electromagnetic interference shielding effectiveness with alignment of spinnable multiwalled carbon nanotubes

This research develops a unique material to attenuate electromagnetic interference (EMI) by using spinnable multiwalled carbon nanotubes (MWNTs) combined with bio-polydimethylsiloxane (PDMS) that contains BaTiO3 (MBPBT). In particular, a plaid pattern, formed by the spinnable MWNTs, is very effective in attenuating the propagation of EM waves,which achieves over 20 dB at 8.2–12.4 GHz (X-band frequency range). This means that a filter type of the spinnable MWNTs is actively able to handle the directionality and movement of EMI propagation. In addition, the MBPBT is characterized by its strong mechanical advantage (bending radius 180°).

Relationship between the velocity of hypersonic vehicles and the transmission efficiency of radio waves

ABSTRACTAnalyzing the flow field distributions around a near-space blunt-cone vehicle at different flight speeds, we observe that, when the flight speed exceeds a certain threshold, the relationship between the flow field density and the vehicle speed presents a characteristic opposite to that at the flight condition of the speed lower than the threshold. On this basis, the Runge–Kutta method is applied to solve the ray equations in non-uniform plasma, in which the electron density at any computing point is obtained by the Lagrange interpolation based on the discrete data of the flow field. Then the EM wave attenuation in the sheath is determined by the subsection integral method combining with the electromagnetic theory. The numerical results also show that when the flight velocity is lower than the threshold, the energy transfer efficiency of the EM waves decreases with the increase of the vehicle velocity. However, when the flight speed is greater than the threshold, the energy transfer efficiency increases as the vehicle speed increases. This conclusion will be helpful to further understand the EM wave propagation characteristics for hypersonic vehicles, and to provide a reference for the channel selection of antennas.

Channel characterization of EM waves propagation at MHz frequency through seawater

SummaryElectromagnetic (EM) communication is considered as a suitable physical layer choice for SeaWater. SeaWater EM communication presents advantages over acoustic and optical in shallow water and deep oceans.Theoretical analysis of EM wave propagation in SeaWater helps us to estimate maximum distance covered in SeaWater at multiple depth points up to 5500 m. Mathematics of EM propagation in SeaWater (conducting medium) shows dependence on f (Hz), ϵ (F/m), and σ(S/m) of transmission medium. This paper presents channel characteristics of EM waves propagation at 1 to 20 MHz frequency through SeaWater based on real time data of SeaWater T (C°) and S(ppt) for averaged decades from 1955 to 2012 up to 5500 m.We estimated SeaWater σ (S/m), ϵr (F/m) (using Stogryns model), α (Np/m) (using Helmholtz model), Z(ohms), fT(Hz), vp(m/second), τ(second), and Pr(dBm) (using Maxwell equations and Friis law). Analysis of these parameters against multiple depths of SeaWater and frequencies shows that we can not assume constant σ (S/m) (4), ϵr (F/m) (81), fT (Hz) (888 MHz),vp(m/second) (3.33∗107), and τ (second) (8.2∗10−12) for SeaWater. Estimated Pr(dBm) helped us to analyze that for lower transmission frequencies (means higher ) and for lower σ(S/m), Pr(dBm) decays linearly. While for higher frequencies (means lower ) and for higher σ(S/m), Pr(dBm) faces sudden exponential decay. That negates sudden exponential delay (in general) of Pr(dBm) in SeaWater; it was only possible by assuming constant SeaWater ϵr (F/m) and σ(S/m). Our paper illustrates radio frequency communication for SeaWater in 1 to 20 MHz range and also provides comprehensive performance analysis using MATLAB simulation tool.

Design and analysis of an ultrathin triple-band polarization independent metamaterial absorber

In this paper, an ultrathin triple-band polarization insensitive metamaterial (MTM) absorber has been presented for C-band applications. The proposed structure is explained as a combination of two absorbers, named as Absorber-I and Absorber-II. It exhibit 91%, 98.9% and 99.5% absorptivity at 4.2 GHz, 7 GHz and 7.4 GHz frequencies respectively. Absorber-I and Absorber-II are individually responsible for the origin of two separate frequency bands at 4.2 GHz and 7 GHz respectively. Further, mutual coupling between Absorber-I and Absorber-II is responsible to generate one more absorption band at the frequency of 7.4 GHz. The fourfold symmetric nature of the proposed unit cell provides polarization insensitivity phenomena. The absorbing mechanism of the designed absorber has been explained by two methods. One is by plotting input impedance of the absorber. Another one is by analyzing the EM wave propagation inside the structure. The proposed absorber has been fabricated and simulation results are experimentally verified.

A new method to analyze the EM wave propagation characteristics in the hypersonic sheath

A new method is proposed to study the characteristics of the electromagnetic wave propagation in inhomogeneous media, which is then applied to investigate the EM wave propagation characteristics in the hypersonic sheath. In the aspect of modeling, based on the spatial distribution features of the model data, the dimension reduction method is proposed, which can transform the processing of high-dimensional data into the processing of the one-dimensional data, greatly reducing the computational complexity and avoiding a large amount of data query. In the aspect of the EM algorithm, the electromagnetic ray equations in inhomogeneous medium are introduced into the analysis of the wave propagation characteristics in the hypersonic sheath; on this basis, combining the theory of EM wave propagation with numerical methods such as the Runge-Kutta method and the Lagrange interpolation method, and so forth, the ray equations in the sheath are solved numerically. Finally, according to different flight conditions, the characteristic of the EM wave propagation in the sheath is exhibited in detail. Compared with other methods, the method proposed in this paper has many advantages such as low computational complexity and high computational efficiency. Thus it will provide a reliable algorithm support for the related applications in engineering.

Sparsity‐based SFCW‐GPR autofocusing imaging method under EM wave velocity uncertainty

To tackle the problem of the uncertainty of EM wave propagation velocity in the subsurface medium, a novel sparsity-based autofocusing imaging method for stepped frequency continuous wave ground penetrating radar system is proposed. On the basis of the parametric sparse recovery method, the proposed imaging method exploits the sequential L 0 and L 2 norms minimisation strategy to simultaneously retrieve the EM wave propagation velocity information and the high-quality focused image. Experimental results demonstrate the validity and effectiveness of the proposed imaging method.

Interaction of plasma and electromagnetic waves in warm motional plasma: Local approximation method

The behavior of short-wavelength electromagnetic waves passing through a warm motional plasma is studied. The velocity and the self-magnetic field of the plasma particles are directed transversely to the direction of wave propagation. Using local approximation method, dielectric tensor and dispersion relation of perpendicular waves are derived employing the Fluid-Maxwell model. The role of temperature in propagation of EM waves, and as a result, in the instability caused by interaction between extraordinary EM waves and modified electron plasma waves is demonstrated. Moreover, the effects of self-magnetic field strength on the instability are illustrated.

Recent Advances in Numerical Simulation of Propagation of EM Waves in the Earth's Ionosphere

EM wave propagation in the magnetoactive terrestrial ionosphere was investigated by numerical methods, and associated software was developed. Two principal functions were realized: ray tracing and ionogram synthesis. For the first time, reference-standard models, including the International Reference Ionosphere (IRI) 2012, World Magnetic Model 2010, and World Geodetic System 1984, have been globally implemented for every component of the propagation medium, and fully manipulatable 3-D visualization was enabled in a study utilizing the bicharacteristic method. An assimilation model of the ionosphere was also used along with IRI. The focus was on the unveiling of multiskip long-range propagation effects. Effective numerical algorithms for solving the bicharacteristic system that allow rapid insight into an extremely large-scale EM problem and enable quasi-real-time operation were discussed. The simulation in the presence of abnormal locally increased or decreased electron density in the ionosphere of natural or artificial occurrence was considered. Experimental ionograms obtained by an ionosonde were compared to numerically synthesized ones.

Modeling and Synthesis of 3-D Water Vapor Fields for EM Wave Propagation Applications

Stochastic model of water vapor (SMOV), a methodology to generate realistic 3-D spatially correlated water vapor fields, is presented, which is devised by investigating remote sensing observations acquired by the MODIS sensor (Aqua satellite). Synthetic water vapor fields are $200~\text {km} \times 200$ km, with $1~\text {km} \times 1$ km horizontal spatial resolution, while the water vapor content $v$ extends up to 20 km with a vertical sampling of 100 m. The field synthesis relies on the stochastic approach proposed by Bell and requires as input the average integrated water vapor content provided with coarse spatial and temporal resolution by numerical weather prediction (NWP) products. The vertical profile of $v$ is modeled as a simple exponential function decreasing with height, as observed from typical radiosonde observations and NWP data. Tests on the model’s accuracy show that both first-order (complementary cumulative distribution function) and second-order (spatial distribution) statistics of the integrated water vapor content are closely reproduced in several European sites. Results corroborate the use of SMOV as part of a comprehensive simulator of atmospheric impairments, which aims at taking into account all the constituents affecting the propagation of millimeter waves in different scenarios, including applications involving very low elevation links such as unmanned aerial vehicles and low Earth orbit satellites.

Temperature induced in the testicular and related tissues due to electromagnetic fields exposure at 900 MHz and 1800 MHz

Increased testicular temperature adversely affects the reproductive system in the male. Environmental conditions, namely high ambient temperature and electromagnetic fields (EMFs), influence the temperature increase in the human body. This study considers the computationally determined specific absorption rate (SAR) and the heat transfer in a piecewise-homogeneous human model of the male reproductive organs and upper thigh exposed to an electric dipole antenna. The study focuses on increases in testicular temperature due to EMF absorption. Much attention is paid to the effects of the operating frequency and exposure time on the SAR and temperature increases induced by exposure to a near-field EMF. The electric field, SAR and temperature distributions in various tissues during exposure to EMFs are obtained by numerical simulation of EM wave propagation and an unsteady bioheat transfer model. This study indicated that when the model is exposed to EMFs at the frequencies of 900 and 1800MHz, the highest SAR values are obtained in the scrotum. In the testis, which is the most sensitive part of the male reproductive system, the SAR value of the 900MHz frequency is significantly higher than that of 1800MHz, while there are no significant differences in the temperature increases between the two operating frequencies. The obtained results may be of assistance in determining exposure limits for the power output of wireless transmitters, and their operating frequency for use with humans. Significant of this workThe study focuses on increases in testicular temperature due to EMF absorption. Much attention is paid to the effects of the operating frequency and exposure time on the SAR and temperature increases induced by exposure to a near-field EMF. The electric field, SAR and temperature distributions in various tissues during exposure to EMFs are obtained by numerical simulation of EM wave propagation and an unsteady bioheat transfer model. The obtained results may be of assistance in determining exposure limits for the power output of wireless transmitters, and their operating frequency for use with humans.

Design of split ring antennas for WLAN and WiMAX applications

ABSTRACTThis paper compares the design of two compact monopole antennas based on metamaterial inspired split ring structures. The effect of orientation of split axis to the direction of an incident EM wave is discussed. When the axis of the split is parallel to the direction of EM wave propagation, it results in a narrow band creation and when it is perpendicular, it leads to a notch frequency. Antenna 1 is intended for WLAN (2.4/5.2/5.8 GHz) application whereas antenna 2 operates on both WLAN and WiMAX (3.5 GHz) frequency bands. Both the antennas are printed on a 30 × 30 × 0.8 mm3 FR‐4 substrate with a partial ground plane and is fed by a microstrip line. The structures mainly differ in their split positions. Analysis of the split ring structures is also discussed. Prototype of the proposed structures are fabricated and the measured results comply greatly with the simulated results. The antenna has consistent radiation pattern over all the working region. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2117–2122, 2016

Evaluation of transformer core contribution to partial discharge electromagnetic waves propagation

Accurate Partial Discharge (PD) measurement requires the expansion of the measurement frequency range to Ultra High Frequency (UHF) band. For this it is needed to implement modern techniques when monitoring an important element of power system, such as power transformer. Different kind of experimental models, such as insulation defect models, and the complete transformer windings models are used to simulate the partial insulation failure situations which occur in a real transformer. However, since in these models, some kind of simplifications are employed which may result in an electromagnetic waves (EM) propagation pattern different from what exists in a real transformer and encounter errors in its PD measurement results. In this paper, the transformer core effects on PD EM wave propagation are investigated. To address this concern, different core designs are simulated. Finite Integration Time (FIT) method is used for electric field calculation through application of Microsoft CST microwave studio Software. The probes recorded electric fields are analyzed using wavelet transform (WT). A new approach based on energy scale coefficient (for each decomposition level) is used for mother wavelet selection. Results of these simulations demonstrate how existence of core and its design affect the characteristics of measured PD signal.

Applicability of Ground Penetrating Radar on desert archaeological sites: a case study from the Saqqara necropolis in Egypt

Abstract This paper presents the preliminary results of ground penetrating radar sounding applied at the desert archaeological site in Saqqara (Egypt). The survey was carried out in 2012 within a project realized by Institute of Archaeology, Cardinal Stefan Wyszyński University in Warsaw and the Faculty of Geology, University of Warsaw. One of the key aims of the research was testing the application of ground penetrating radar to non-invasive surveys of desert archaeological sites. Radargrams obtained for area of so called the Dry Moat channel surrounding the Step Pyramid complex have shown the geological structure of its filling. It comprises among others debris-sand conglomerate of diluval origin characterized by a significant content of the clay fraction and clay minerals. Such lithological content strongly attenuate the propagation of EM waves, restricting the depth range of the GPR survey. The conducted geophysical prospection west to the Step Pyramid in Saqqara has confirmed the high applicability of the GPR method in non-invasive studies of vast architectural structures, such as the monumental ditch surrounding the Step Pyramid known as the Dry Moat. It should summarised that high horizontal resolution obtained during GPR survey is a result of local geological structure of the searched area, i.e. strong lithological contrast of the sediments filling the Dry Moat, which, depending on their mineralogical composition

EM Wave Propagation in Non-uniform Soil

EM Wave Propagation in Non-uniform Soil