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Due to the fields in the near-field area of an electric dipole source which is sharply and rapidly varying with distance, a novel approach to introduce an underwater low-frequency excited source is proposed in this paper. The approach is built up to combine the theoretical solution for an electric dipole in a conductive medium with the total-field scattered-field boundary to reduce the error in modeling the source. The spatial distributions of the magnetic field amplitude at a distance of 1 km above the sea surface are discussed. The numerical results verified the accuracy and validity of the approach by comparing with the results of the Sommerfeld numerical integration method.

The characteristic frequency from the low-frequency scattered fields was discussed when a pulse source is adopted to irradiate an underwater target. The total-field scattered-field source finite-difference time-domain (TSS-FDTD) method is used to analyze the scattered fields from the underwater target. Numerical results illustrate the characteristic frequency from an underwater metallic spheroid.

The Sommerfeld numerical integral method (SNIM) is used to study the electromagnetic fields of an electric dipole under sea surface in this paper. The spatial distribution of electromagnetic field amplitude on the 1km plane away from the sea surface is discussed with a horizontal electric dipole of 100m below sea surface. Numerical results shows that the accuracy and validity of the approach are verified by comparing with the results of the Finite Difference-Time Domain (FDTD) method.

Micromotion characteristics of conical-shaped high-speed moving targets are presented using the Lorentz finite-difference time-domain (Lorentz-FDTD) method. This research discusses the transformation formulas of the space and time increments, the incident wave, the field components between the moving system, and the laboratory system in case of a micromotion target. The validity and accuracy of the proposed transformation formulas are verified by presenting the results for a moving cone and a hemisphere–cylinder combination target.

Traditional explicit and unconditionally stable FDTD uses electric iteration formula to get the change of electric and magnetic fields. In this work, we show that the change of magnetic field can be obtained by magnetic field iterative equation in 2-D unconditionally stable FDTD method. Numerical experiments have demonstrated the stability and efficiency of the proposed method.

Electrical impedance tomography is a non-invasive, safe, portable imaging technique that enables images of electrical impedance to be reconstructed from voltages measured with an array of electrodes placed on the boundary. Typically, an image data set is collected as a series of many impedance measurements designed to sample as much of the volume as possible. The method, as a typical method for geological studies, is applied for submarine target detection. A method based on complete electrode model and singular-value-decomposition method is applied to reconstruct the conductivity distribution of the DOI. Some numerical results are presented with detailed discussions.

This paper focuses on the characteristics of electromagnetic waves in dusty plasma. On the basis of verifying the feasibility of the propagation matrix method used in dusty plasma, we layered the plasma and then found the basic law of electron concentration which is one of the factors affecting transport properties of wave.

Early Access; International audience; Acousto-electric tomography (AET) involves three steps to retrieve the distribution ofconductivity in a domain of interest (DOI): measure the potential on the DOI boundary (usually with alimited number of electrodes set there), compute the power density from this potential, use it to retrieve thedistribution sought after. Almost all developed algorithms for AET assume that the power density is known,so their focus is mostly on the last step. A complete framework for AET is proposed herein to connectthe three steps, the complete electrode model (CEM) being used to simulate the voltages measured onelectrodes. The potential on the whole DOI boundary is reconstructed from such voltages. Then, the powerdensity is computed, and the conductivity distribution in the DOI retrieved. A method based on singularvalue decomposition (SVD) is proposed. This method and the iterative Levenberg-Marquardt method areused for numerical illustration. The SVD-based method yields the potential on the whole DOI boundary,and a gross map of the conductivity distribution is also obtained, to serve as initial guess of the Levenberg-Marquardt method to yield the conductivity contribution with higher accuracy.

To implement the Lorentz finite-difference time-domain (FDTD) method in a 3D case, this communication presents the transformation formulas of the spatial and time increments, the field components, and the incident plane wave between the moving system and the laboratory system. The radiated fields from a moving dipole source are shown to verify the accuracy and validity of the proposed transformation formulas. The relative errors are within an acceptable range. The scattered fields of a moving metallic sphere are also illustrated to verify the validity of the proposed method. And, the scattered fields from a complex pyramid-shaped target are discussed.

In this paper, a novel non-illuminated Graphical Electromagnetic Computing Method (NI-GRECO) based on GPU acceleration has been proposed. It has the advantages of high accuracy and efficiency compared to the traditional GRECO method, and does not suffer from the limitation in the illumination model anymore. In this NI-GRECO we also proposed a pixel subdivision technique, which can improve the display accuracy of the target model and then increase computing accuracy. In case of the data output, the method of data extraction by using the Frame Buffer Object (FBO) can also improve computing accuracy. In this way, the data output is no longer subject to color restriction. The extraction accuracy of the normal vector increased from 1/256 to 1/1000000. Additionally, the novel method has a significant speedup, which is up to 36 times than the original GRECO method for a sphere RCS simulation thanks to the parallel GPU processing.

An impulse plane wave is introduced in Lorentz finite-difference time domain for calculating the fields of high-speed moving dielectric. Applying the impulse plane wave and the fast Fourier transformation, we can directly read out the frequency shifts of the reflected and transmitted waves by one-time calculation. The proposed approach can greatly save run time and enhance the computation efficiency, especially in terms of considering a large number of incident frequencies. Two cases of moving canonical and noncanonical dielectric targets are considered to verify the accuracy and validity of the proposed method.

This paper extends the FDTD method to calculate the micro-motion characteristics of a moving cylinder by combining the Lorentz transformation and the central interpolation technique. The validity and accuracy of the proposed method are verified by the calculation results of the cylinder in a micro-motion state.

In this paper, the number of the wire grids and the length of the metallic plate in a bounded wave simulator are discussed. Five cases for the number of wire grids and three cases for the length of the metallic plate are simulated. By comparing the results of the all-plate model, the model with the length of 10m and the wire-grid number of 26 is almost equivalent to the original model with a little difference.

A voltage source is inserted into the surface of a metallic ship with the TSS-FDTD method to calculate the phase distribution of low-frequency surface current along the ship. The phase distribution of the surface current in f=10Hz is discussed with the proposed method. Numerical results show that the phase distribution is periodic round the voltage feed.

In this paper, a method for detecting the shape and position of object embeded in a conductive closed-domain with the acousto-electrical tomography is presented. Due to the difference of conductivity between the inclusion and the background material, we create a forward model to obtain the spatial potnetial distribution in the entire domain. Then, with the Levenberg-Marquardt algorithm the conductivity distribution is reconstructed by applying in the spatial potential distribution. A two-dimensional example is illustrated. Numerical results show that the shape and location of object in the domain can be clearly reconstructed.

In this paper, the different combinations of the numbers of wire grids in a bounded wave simulator are discussed. The wire grids are divided into five sections. These sections are provided with the same projection lengths and different numbers of wire grids. By comparing the simulated results of the all-plate model and the model of bounded wave simulator with 26 wires, the proposed model of bounded wave simulator with 26, 26, 14, 26, 18 wires for five sections, it is shown that the results of the proposed model are in more agreement to the all-plate model .

We apply the parallel TSS-FDTD method to obtain the spatial distributions of fields in air radiated from an underwater magnetic dipole source. The equivalent principle is used to calculate the far fields in a far zone by recording the tangential electromagnetic fields on a virtual surface above the air-sea surface. Numerical results show that the presence of sea surface affects the spatial distributions of electric field along the propagation direction.

In order to improve the computation efficiency for analyzing the underwater electromagnetic propagation at low frequency, a novel parallel total-field scattered-field source finite-difference time-domain (FDTD) method is presented in this letter. The accuracy and validity were verified by comparison to the analytical solution. Numerical results show that the parallel speedup of 13.68 and efficiency of 68.4% are obtained with 20 processors.

In order to precisely calculating the fields in air from an underwater magnetic dipole source, a novel method to introduce a low-frequency source is proposed. This method is built up by combining the analytical solution of the magnetic dipole source in the conductive medium with the total-field scattered-field boundary condition. Numerical results verified the validity and accuracy of the proposed method.

The scattered properties in the far-field region of an ellipsoid target., moving at high speed., are presented by a three-dimensional Lorentz Finite-Difference Time-Domain (FDTD) method. When the target is rest., the results are in good agreement with those by the MoM method and the conventional FDTD method. Numerical results show that the radar cross section (RCS) in the far-field region from the moving target is modulated by the moving speed.

A cascaded total-field scattered-field source finite-difference time-domain (TSS-FDTD) method is used to analyze the underwater propagation properties of a low-frequency electromagnetic wave. In order to obtain the long-distance electromagnetic fields, two or more steps FDTD calculations are included. The relationship between two times FDTD calculations is the field data exchange on the TSS boundary. The grid ratio of two times calculation spaces can be set to an arbitrary positive odd integer, for instance N=5. The numerical results verify the accuracy and validity of the proposed method.

The scattered properties of a three-dimensional almond-shaped target, moving at high speed, is analyzed by the Lorentz-FDTD method. Numerical results show that the amplitude and frequency of the scattered wave are modulated due to the moving speed of the target.

The scattered properties of a cone-sphere target, moving at high speed, are presented by a three-dimensional Lorentz-FDTD method. Numerical results show that the amplitudes of the scattered wave are modulated by the movement of target. Moreover, different operating frequencies cause different amplitudes of scattered wave for the same moving speed of target.

A lossy Drude dispersive medium is used to analyze the propagation properties of the low-frequency electromagnetic wave under the rough sea surface. Numerical results in f=150Hz are illustrated for two different rough sea surfaces. It is noted that the rough sea surface affects the phase and amplitude distributions of the low-frequency electromagnetic wave.

A novel three-dimensional total-field scattered-field source finite-difference time-domain (TSS-FDTD) method is presented to analyze the propagation properties of low-frequency electromagnetic wave in underwater. The proposed method includes two-step FDTD calculations. The first calculation space is meshed with a fine cell size. The second is meshed with a coarse cell size. In addition, the ratio of a coarse cell size to a fine cell size is set to an arbitrary positive integer, such as $N=11$ in this letter. Numerical results prove the accuracy and validity of the proposed method. An analysis of the results shows that the run time spent in TSS-FDTD accounts for 0.35% of that in the conventional FDTD, and the consumed memory is 3.9% of that spent in the conventional FDTD.

In order to reduce the consumed run time for analyzing the propagation properties of a low-frequency electromagnetic wave in air or seawater, a novel approach of modelling the sea and the air with a lossy Drude dispersive medium is proposed. The numerical results verify the accuracy and validity of the proposed approach. The run time consumed can be reduced by increasing the time interval in the proposed approach.

In order to reduce the calculation time step in low frequency, a novel approach of modelling mediums with a lossy Drude dispersive medium is proposed. Numerical example illustrates the scattering properties of underwater targets with different shapes in f=110Hz and f=150Hz.

With a novel three-dimensional Lorentz-FDTD method, we discuss the radiated fields of a moving dipole source at high speed. Different from the close-form solution, the Lorentz-FDTD method can be used to analyze the radiated fields of moving targets of complex structure. In this paper, we deduce the iterative formulas of Lorentz-FDTD in the three dimensional case. In a case of considering the radiating fields of a moving dipole source, a good agreement is achieved. The accuracy and validity are also verified.

Calibration is important to service robot, but the process of calibration is time consuming and laborious. With the popularity of service robot, an automatic and universal calibration system is urgent to be developed, therefore we propose a general batch-calibration framework, Motion Capture System is adopt as an external measurement device in virtual of it can provide realtime, accurate movement data of measured objects. We will show that the system is effective and promising with a case study of odometry calibration.

Nowadays there are a lot of kinds of cleaning robots which producted by different manufacturers come into people’s lives. But it is still a problem that how to evaluate each robot’s performance to check whether the quality is acceptable. In this paper, we make the first trial to evaluate the complete coverage path planning algorithm which is the core algorithm of a cleaning robot with Mocap system, and three simple metrics were proposed to evaluate overall performance of the algorithm. Lastly, the comparisons between different kinds of robots are presented.

Based on the conventional finite-difference time-domain (FDTD) method, a novel total- field scattered-field source FDTD method with a dual-meshed technique is presented to deal with the underwater detection problems in low frequency electromagnetic wave. A transformation surface connecting the coarse cell with the fine cell is implemented by applying a total-field scattered-field source (TSS) technique, which is carried out by two-step FDTD simulation. The ratio of a coarse cell size to a fine cell size can be set as an arbitrary integer, such as N = 10. Moreover, an analysis of numerical error illustrates that non-physical reflection fields from the TSS surface are avoided by introducing the TSS surface. We have derived, in detail, the update equations of fields on grids of the TSS surface. Three cases of dealing with different underwater electromagnetic problems are discussed. Numerical results show that by analyzing the magnitude and phase of scattered fields from obstacles underwater we can distinguish the category of the obstacles which belong to either a high resistivity body or a low resistivity body. Therefore, the proposed method provides us an effective tool for analyzing the electromagnetic response of materials underwater.

In this paper, the coefficients of reflection and transmission of high-speed dielectric target is discussed by Lorentz-FDTD method. In this method, two coordinate systems are defined, one is the laboratory coordinate system, marked by K; another is the moving coordinate system, marked by K'. The Lorentz transformation and interpolation are used to connect the laboratory coordinate system and the moving coordinate system. The electromagnetic reflection and transmission coefficients of high-speed dielectric target are calculated. By comparing the simulation result and the analytical result, it is shown that there are a good agreement between the simulation results and the analytical results.

In order to further detect underwater targets, such as oil, gas, and shipboard equipment and so on, we discuss the underwater radiation fields of a magnetic dipole array with 3×3 elements in the TSS-FDTD method. Numerical results show that the H z and E z amplitude and phase snapshots are symmetrical related to the z axis in the yoz plane in the working frequency f=180Hz. By analyzing the radiated fields, it is more readily to distinguish if there is an abnormal underwater target or not.

To analyze scattering fields from moving conducting bodies, a novel Lorentz finite-difference time-domain (FDTD) method is proposed in this paper. The transformation formulas of electromagnetic field parts, space parts, and time variable are gained by using Lorentz transformation between the rest and the moving reference frame. To calculate the scattering fields from moving conducting bodies, the total-field–scattered-field boundary condition is set up to introduce an incident plane wave in the moving reference frame. Using the interpolation method, the relation between electromagnetic fields in the moving reference frame and that of the related grids in the rest is estimated. Using the proposed Lorentz-FDTD method analyze the scattering fields from one-dimensional moving conducting surface. Thus, variations of the amplitude and frequency of scattering fields with the moving conducting surface speed are considered. Caused by the moving conducting surface, the amplitude and frequency of incident plane wave...

A chip antenna for Bluetooth applications is proposed. This antenna has three symmetric metallic layers implemented by low-temperature co-fired ceramic (LTCC) technique. Because of the symmetric structure, there is no need to mark the polarity of the antenna. No vias are required in the antenna, which leads to significant simplification of fabrication process. This is achieved by connecting the metallic layers using electrodes at two ends. The antenna behaves as a quarter-wave monopole loaded with inductors and the radiating area is the whole straight metallic strip in the middle layer, so the radiation pattern is omni-directional. The size of the antenna is only 9 × 2 × 1 mm3 at 2.45 GHz. The proposed antenna design is assessed by comparing the related simulated and measured results. The measured results show that the bandwidth of the antenna is 100 MHz (corresponding to 6 dB return loss) and the gain is 1.3 dBi. Measured results validate the novel design of the proposed antenna. In addition, the paramet...

A novel single layer planar gain-enhanced antenna radome is presented to overcome the low gain disadvantage of microstrip antenna. Seven same microstrip complex structures were arranged as a planar centrosymmetric honeycombed shape and accordingly etched on the surface of FR4 substrate. By extracting the constitutive parameters of unit cell of the proposed antenna radome, the value of effective permittivity of unit cell turned out to be near zero at frequency f = 4.25 GHz. The proposed radome design is assessed by comparing the related simulation and measurement results. Gain of the antenna with the new radome design is enhanced with a growing range of 2.5 dB. Results offered in this paper validate the novel design of the proposed antenna radome.

The conventional perfectly matched layer (PML) absorbing boundary condition is shown to be unstable when it is extended to truncate the boundary of the double negative (DNG) medium. It is a consequence of the reverse directions of the Poynting and phase-velocity vectors of plane waves propagating in such material. In this paper, a modifled uniaxial PML (UPML) which is stable for the DNG medium is derived. The auxiliary difierential equation technique is introduced to derive the discrete fleld-update equations of DNG-UPML. Numerical results demonstrate the efiectiveness and stability of the new UPML for the DNG medium.

In order to extend the reach of a conventional FDTD simulation without using extraordinary computer resources, a large scale of fine to coarse cell transformation for 3D FDTD Simulation is presented in this paper. With the proposed method, numerical results are discussed in the three-dimensional case. It proved that the proposed method is of accuracy and high efficiency by comparing with analytic solution and conventional FDTD.