The currents flowing through a transmission line produce a rotating magnetic field of vertical and horizontal components which are orthogonal in space and vary with time. Buried and aerial metallic pipelines that run parallel to or are placed in the vicinity of overhead AC high voltage transmission lines are affected by this field resulting in an induced voltage on the pipelines. Several related studies and safety standards dealing with this problem have been published. Nevertheless on a multi-circuit line, the issue of current phase shift variation has not been fully covered yet. This paper provides a detailed analysis of the effect of current phase shifts on the magnetic field distribution and polarization pattern around power lines using analytical approach from electromagnetic field theory. In this study, not only the variation of the filed distribution with phase arrangements and phase shifts is further established, but also the characteristic nature of the variation of the field distributions for six phase arrangements is examined in more detail. The results show that the magnetic field distribution at the ground level and the spatial distribution of the magnetic field polarization ratio vary significantly with the phase sequence arrangement as well as the current phase shifts between the two circuits. The field polarization differs at different locations. The information from the results can be useful for consideration in designing an effective AC mitigation technique and in placing pipelines in the utility corridor with power lines. Pipelines should be placed in a region of minimum field intensity within the right-of-way of the line, in order to have minimal induction on the pipeline in normal operating conditions of the line.

Point target detection in space-based infrared (IR) imaging system is an important task in many applications such as IR searching and tracking and remote sensing. Although it has attracted great interest and tremendous efforts during last decades, it remains a challenging problem due to the uncertain heterogeneous background and the limited processing resources on the onboard platform. Aiming at this problem, a novel background suppression method based on multi-direction filtering fusion is proposed in this paper. The process of background prediction for each pixel by this method can be divided into two steps. Firstly, eight predicted values are obtained by using linear filtering methods along eight different directions respectively. Then, Gaussian weighted sum of the eight predicted values is computed to generate the final result. We conduct several groups of experiments on different categories scenes with simulated targets, and the final experimental results demonstrate that our methods can not only obtain state-of-the-art performance on background suppression (especially for heterogeneous backgrounds), but also detect targets accurately with low false alarm rate and high speed in IR point target detection tasks.

In this paper, a CPW-fed circular patch UWB-extended bandwidth antenna is proposed which is fabricated and characterized on silicon. The proposed antenna covers fractional bandwidth of 132.08% with high rejection triple band-notch characteristics [WiMAX(3.30 GHz-3.80 GHz)/WLAN(IEEE802.11a/h/j/n 5.15 GHz-5.35 GHz, 5.25 GHz-5.35 GHz, 5.47 GHz-5.725 GHz, 5.725 GHz-5.825 GHz)/X-band downlink satellite communication system (7.25 GHz-7.75 GHz)]. Gain and efficiency of the proposed antenna in the entire bandwidth vary between 3.96 dBi-10.98 dBi and 84%-95%, respectively. Also, group delay in the entire operating band is ≤ 1.0 ns. Furthermore, the proposed antenna exhibits good dipole like radiation pattern in E-plane and omnidirectional pattern in H-plane with small dimension of 20×20×0.5 mm³.

Aimed at solving the problems of high initial cutoff frequency, small stopband range and poor inhibition in the current electromagnetic band gap (EBG) structure, an electromagnetic band gap structure designed on the basis of periodic Z-bridge EBG inserted by a double complementary slit ring resonator (DBCSRR) cell is proposed. Compared with the traditional EBG structure, the proposed EBG structure can achieve 270 MHz-20 GHz bandwidth in a reference of -30 dB, which is wide in range. The measured and simulated results indicate the wideband of noise suppression. In addition, the lower and upper cutoff frequencies are estimated by using equivalent circuit models, respectively. Moreover, the IR-Drop and dc resistance is accurately investigated through 3-D simulations. Finally, the transfer characteristics of single signal line are studied.

Based on metamaterials and compressive sensing theory, we design a single pixel millimeter-wave fast imaging system by a 1D aperture array. The aperture array is realized by a column of complementary electric-lc (cELC) units etched on amicrostrip transmission line. Each cELC unit resonates at a different frequency, where the energy is coupled from the aperture to free space. A sequence of random field patterns can be obtained by controlling geometric parameters of each cELCunit. We use the frequency as the index of measurement matrix which well satisfies the restricted isometry property (RIP) and is well suited for compressive sensing (CS). A prototype of CS imaging system operatingatKa-band (27-40 GHz) is fabricated which can detect a 5 cm * 5 cm object precisely at a distance of 50 cm.

An extremely wideband photonic crystal antenna is proposed with a very compact size of 16.6 x 26.6 x 0.9mm³. The double-layer materials of silicon and glass are selected as the antenna substrate. The band gap performance of photonic crystals can decrease electromagnetic wave absorption of silicon substrate, restrain surface wave loss of antenna, and increase electromagnetic wave space radiation. Hence the periodical photonic crystal with square lattices is applied in upper silicon substrate. The glass substrate not only decreases effective dielectric constant of antenna, but also supports silicon substrate with photonic crystal. MEMS processes are used to realize photonic crystal antenna with plenty tiny through-holes. The simulated and measured results demonstrate that photonic crystal can effectively expand the working bandwidth of base antenna.

This paper analyzes rectangular and circular patch antennas fabricated from meshed conductors and backed with solid ground planes. Because of the meshing, the antennas are rendered optically transparent, where the transparency is determined by the mesh geometry. It is found that although there is a compromise between the antenna's efficiency and the optical transparency of the meshed patch, it is possible to optimize the antenna by refining mesh lines to certain extent. The limiting factors for refining mesh lines include material handling and fabrication process as well as the increased line impedance when being refined, which accordingly causes loss in antenna's efficiency. A refined mesh with thin linewidth increases both antenna performance and transparency. Additionally, it is found that the reduction of certain mesh lines increases the optical transparency with minimal hindrance to the antenna's efficiency, leading to further enhancement to the see-through percentage. Although it is possible to refine mesh lines to improve the antenna's efficiency or gain, it is seen that there is a limit for such an optimization method. This limit is closer to the efficiency of a solid patch for a lower transparency, whereas it is lower for increased transparency. Cross polarization level was also examined, and there was no signifficant efft on such a parameter due to meshing.

This paper aims at designing a wideband planar inverted F antenna (PIFA). The design of a PIFA begins with an elementary step such as the etching of antenna element pattern in a metal trace. After the etching adherence is developed by incorporating bonding between it and a printed circuit board which is primarily an insulating dielectric substrate. A ground plane is developed by a prolonging metallic layer which is adhered to the opposite side of the substrate. The simulation is done using ANSYS HFSS full wave 3D simulation software. The proposed PIFA is very compact and also provides a gain of 2.86 dB. As a consequence of the exemplary feature like an omnidirectional radiation pattern, there is an exceptional improvement in coverage. Moreover, the frequency bands covered by the PIFA are for applications including USPCS, UMTS, ISM/Bluetooth and WLAN at (1.85 to 1.99) GHz, (1.90 to 2.20) GHz, (2.4 to 2.485) GHz and (5.1 to 5.90) GHz, respectively.

In this correspondence, the two-dimensional (2-D) direction-of-arrival (DOA) estimation problem for partially polarized (PP) signals is considered. In particular, we focus on an array geometry containing three identical uniform linear arrays (ULAs). Compared with existing methods, the proposed one has three main advantages. Firstly, the estimation accuracy is higher since it exploits the polarization information. Secondly, it can work effectively under the coexistence of both noncircular and circular signals. Finally, pair matching for 2-D DOA is not required which reduces the computational complexity. Simulation results are presented verifying the efficacy of the algorithm.

A compact directional MIMO antenna operating in 2.4 and 5 GHz wireless local area network (WLAN) bands is presented. The compactness of the proposed multiple-input multiple-output (MIMO) antenna can be attained through using miniaturized antenna elements and meanwhile employing an extremely narrow edge-to-edge inter-element space (3 mm). Two novel miniaturized planar inverted-F antenna (PIFA) elements which share a common ground are designed, and each element has a dimension of 31 mm × 17 mm and a profile of 4.2 mm. By etching three slots on the ground, the port isolation can be significantly enhanced, which can even reach a maximum of 54 dB at 2.45 GHz. A desirable directional radiation pattern is obtained, and the calculated envelope correlation coefficient is better than 0.01.

The development of near-space hypersonic vehicles is confronted with the ``blackout'' problem of the plasma sheath. As electronic density on the leeward surface is lower than that on the windward surface during the reentry process, a low Earth orbit (LEO) satellite may be used to mitigate this problem. In this study, the Iridium system, as a low-orbit relay satellite system, is utilized to evaluate the feasibility of using a LEO satellite. First, the incident angle of the electromagnetic waves radiating from the vehicles to various potential relay satellites is calculated by the STK software. Second, the transmission coefficient of the electromagnetic wave in the plasma is obtained by using the equivalent wave impedance method to present the attenuation effect of the plasma sheath channel. Finally, the attenuation coefficients of each channel between the aircraft and the potential satellite are used as a parameter to select the best relay in the reentry process of the vehicles. Simulation results show that the use of LEO satellites for relay can significantly reduce the communication interruption time during the reentry process by 32.6% for typical scenarios.

This paper describes the design and experimental characterization of a circular polarized printed antenna for dual-band WiFi operation at 2.45 GHz and 5.10 GHz. The patch design is based on a combination of slits loading and gap-coupling applied to a disc patch in order to enhance the radiation performances in terms of polarization purity and bandwidth at the two operation frequencies. Experimental validations confirm a maximum gain around 6.0 dB for both 2.45 and 5.10 GHz, as well as an axial ratio as low as 0.5 dB and a return loss exceeding 15 dB on the operating frequencies. These characteristics are suitable for operationing in IEEE802.11x networks.

Wearable wireless technology has developed as an exciting topic over the last couple of years. With the extensive use of Wearable Wireless Devices (WWD) in greater proximity to the body for various wireless applications, the concern about biological effects due to the interaction of human tissues with the radiations is growing. In this research, we investigate the application of Infrared Thermography (IRT) to obtain temperature dynamics and reconstruct Specific Absorption Rate (SAR) to evaluate the exposure amenability of WWDs. A microstrip monopole antenna on a wearable substrate is used to determine the biological effects of the interaction of electromagnetic (EM) waves on the body. SAR is obtained using EM field simulations and by reconstruction from thermal measurements with the use of Bio-heat equationsfor a continuous exposure of 300 s. Validation of IRT to reconstruct SAR is demonstrated by comparison with EM computations. The maximum SAR was 32 mW/kg, for simulations and 35 mW/kg, from reconstruction after IRT experiments. The maximum temperature change in both cases was always less than 1˚C. The difference between the SAR obtained through IRT and simulation tools accounted for an average of 8.7%. Information acquired using IR temperature dynamics can yield SAR values which can assess radio frequency exposure compliance for WWD at frequencies used for modern wireless technologies, with reliability.

A semi-analytical method to analyze post-wall waveguides and circuits based on the model of two-dimensional photonic crystals formed by layered periodic arrays of circular cylinders is presented. The propagation constant of the fundamental TE mode, the attenuation constant due to the leakage loss and the effective width of an equivalent rectangular waveguide are calculated. Using the concept of the effective width, the original structure is replaced by an equivalent rectangular structure. When additional metallic posts are loaded in the rectangular waveguide, functional post-wall waveguide-based passive circuits are formed. The S-parameters of the post-wall circuits, which act as bandpass filters, are calculated using the image theory combined with the lattice sums technique.

This paper presents the development and design of flexible and conformal printed monopoles antennas. The main objective is to control the level of radiation in broadside antenna from zero to a maximum by changing the curvature of printed board. Two printed antennas types are considered: thin wire and disk monopole. Furthermore, with the curving radius R increasing, the classical null on the broadside radiation pattern disappears gradually for both wire and disk. Increasing the curvature radius of conformal flexible antenna, and keeping all other parameter's value, wire monopole antenna becomes mismatched while the disk monopole antenna remains matched for all radius of curvature. The simulated results of various monopoles are compared successfully with measurements.

A dual-band omnidirectional circularly polarized (CP) patch antenna with conical radiation patterns is presented in this paper. The antenna consists of a patch with inclined slots, a ground plane with L-shaped slots and a coaxial probe. In addition, by loading shorting vias between the patch and the ground plane, the vertical polarizations of the proposed antenna at TM₀₁ and TM₀₂ modes can be obtained. Two sets of slots etched on the ground and the patch contribute to the horizontal polarizations for the two modes, respectively. Omnidirectional CP fields can be achieved at both resonant modes when the two orthogonal polarizations are equal in amplitude and different in phase by 90°. To verify the design, a prototype operating at 2.4 GHz WLAN and 3.5 GHz WiMAX bands has been fabricated and measured. The measured average axial ratios (ARs) at two resonant modes in the azimuth plane are 1.1 and 1.5 dB, respectively. Experimental results show good agreement with the simulated data.

This paper extends the parabolic integral equation method, which is very effective for forward scattering from one-dimensional rough surfaces, to include backscatter. This is done by applying left-right splitting to a modied two-way governing integral operator, to express the solution as a series of Volterra operators; this series describes successively higher-order surface interactions between forward and backward going components, and allows highly efficient numerical evaluation. This and equivalent methods such as ordered multiple interactions have been developed for the full Helmholtz integral equations, but not previously applied to the parabolic Green's function. Equations are derived for both Dirichlet and Neumann boundary conditions (TE and TM).

Effective permittivity and permeability of a medium consisting of an infinite number of ferromagnetic microwires are evaluated in this paper. Analysis is carried out with the help of local and average fields inside a unit cell. In the literature, effective permittivity of the microwire grid is obtained by assuming the grid as an impedance loaded surface. The analysis is applicable only for the case of TM_z polarized normally incident wave. Proposed analysis enable us to evaluate all the three diagonal components of effective permittivity and permeability for arbitrarily incident uniform plane wave having arbitrary polarization angle. Numerical results are obtained through MATLAB, and a comparison is done with the results available in the literature for validation. Numerical results have shown a DNG like behaviour of the medium for a TM_z polarized incident wave.

A low-profile, wideband dual-polarized antenna with unidirectional radiation patterns is the design goal of this paper. To obtain such antenna characteristics, the design is divided into two steps. First, a coax-feed wideband antenna element with a simple geometry is proposed. The antenna element consists mainly of a quasi-square patch-dipole, a coupling E-shaped feeding structure and a shorting pin. The electromagnetic coupling between the feeding structure and the non-contact quasi-square patch can be flexibly controlled by a pair of fan-shaped stubs. Secondly, two pairs of the proposed antenna elements are selected to construct a dual-polarized antenna. To further reduce the profile of the antenna, two techniques are utilized. One is the mutual coupling distributing among the elements while the other is to add four rectangular stubs within the inner region. A prototype of the dual-polarized antenna is fabricated and measured. Measurement results demonstrate that the prototype antenna obtains an overlapped fractional bandwidth of 38.9% from 1.7 to 2.52 GHz with a good isolation higher than 32 dB. Both unidirectional radiation patterns with front-to-back ratios better than 20 dB across the whole frequency band and cross polarization levels lower than -22 dB in most operating frequency band are obtained. Additionally, the dual-polarized antenna achieves average gains about 9.9 dBi and 10.1 dBi for Port 1 and Port 2, respectively.

A novel design of a compact microstrip patch antenna using meandering technique is proposed in this paper where the designed antenna seems to behave as a microstrip patch loaded with conducting strips. A rectangular microstrip patch antenna with addition of conducting strip radiates at much lower frequency than a conventional rectangular microstrip antenna, due to increase of resonant length, but it also causes the increase in total size of the antenna. In this article, the resonant frequency has been lowered significantly by loading a regular rectangular microstrip patch antenna with rectangular slot in a proper position in such a way that the whole structure looks like a strip loaded radiator. About 86.5% size reduction has been achieved experimentally with very good agreement of simulated and measured results. The equivalent circuit and approximate resonant frequency calculation have been discussed in this paper.