Electromagnetic (EM) vortex wave carries orbital angular momentum (OAM), which has been proposed for improve anti-interference performance, spectral efficiency, and message capacity in radio communications. Multiple sub-channels of propagation are achieved by different twisting degrees of EM wave. In order to develop the theory and technique of the OAM, works must be done to study the generation of vortex wave. There exist several devices to generate vortex wave, such as phase plate, holographic diffraction gratings, spiral reflectors, and antenna arrays. In this paper, based on typical parabolic antenna, a new approach to generate vortex wave carrying OAM in radio frequency through coating specific controllable complex dielectric constant material on parabolic antenna is introduced. From the results of the proposed antenna, we conclude that parabolic antenna with materials arranged by a specific rule on the reflector has capacity of generating an EM wave with clockwise and anti-clockwise phase distributions around beam-axis. The new method generating OAM is simple and suitable to be well applied in wireless electronic technology.
The research on implantable ultrasonic coupling wireless power transmission systems has not been systematically analyzed from the sound field theory, and the influencing factors of implanted ultrasonic coupling wireless power transmission systems based on the far-field model are proposed in this paper. Firstly, the far-field model is constructed. On this basis, the main factors affecting the ultrasonic energy transmission in the system are discussed. The COMSOL finite element simulation software was used to simulate the ultrasonic coupling wireless energy transmission system in human tissue environment, and the directivity of the energy transmission system was verified. The system experiment platform is built to analyze the energy transmission under different distances, different sound source frequencies and different sound source excitations, and compare with the numerical simulation data. Finally, the influence of different factors on the energy transmission system is verified. It provides an effective reference for further research on implantable ultrasonic coupling wireless power transmission systems.
This paper is a design and fabrication of an UWB filter (band pass filter) with two notched (rejection) bands. Ultra-wideband (UWB) systems are systems with the electromagnetic spectrum from 3.1 GHz to 10.6 GHz. The designed filter removes WLAN and satellite signals which are 5.8 GHz and 8 GHz. For designing filter, we use a stepped-impedance stub-loaded resonator. To provide two notched bands, a radial stub loaded resonator with a defected microstrip structure (DMS) is used. The presented filter has more analytic relations and simpler structure than prior works. This filter is fabricated on an RO4003 substrate with dielectric constant of 3.55. The dimensions of the filter are 10*25 mm which are more compact than prior structures. The measurements have a good agreement with predicted results which verifies the feasibility of the UWB filter.
In this paper, a differentially fed, structurally simple, patch antenna, operating at 5.2 GHz is presented. The proposed antenna is particularly designed for a base station, Gallium Nitride (GaN) transmitter. The antenna is composed of an H-shaped patch, backed by a ground plane, with two differential feeds placed at the longitudinal edges. The size of the antenna is 0.55λ0 x 0.49λ0 x 0.27λ0 (where λ0 is the free space wavelength at the center frequency). A prototype of the stand-alone antenna is designed, fabricated, and measured. The antenna offers a voltage standing wave ratio (VSWR) bandwidth of 4% and a differential impedance of 100, which matches most of the differential integrated circuits. The measured gain and directivity of the proposed differential antenna are 5.3 dBi and 7 dB, respectively. From simulation it is observed that the proposed antenna possesses a front to back ratio of 15.69 dB and a 3 dB beamwidth of 84˚. The measured peak efficiencies of the antenna in the lower and higher bands are 84% and 59%, respectively. Details of the design and lumped model, along with the experimental and simulated results, are presented and discussed. The effect of scaling different design parameters for operation at different frequency bands is considered as well.
In this paper, a gain and front-to-back ratio (FTBR) enhanced vertically polarized 1 × 3 series-fed linear array for Airborne SAR-X application has been presented. The proposed antenna prototype is designed at 9.65 GHz X-band. The proposed antenna design consists of a square radiating patch, substrate, quarter wave transformer 50 Ω matched transformer, and series feed line (SFL). The simulated antenna prototype is fabricated and successfully measured. The final antenna prototype has a dimension of 80 × 50 × 1.587 mm3 or 2.574 × 1.6087 × 0.051λ03 (Free space wavelength) or 3.256 × 2.035 × 0.0645λg3 (Guided wavelength) at 9.65 GHz. The results indicate that the proposed antenna prototype yields an impedance bandwidth >140 MHz (from 9.591 to 9.712 GHz) defined by S11<-10 dB. The low profile/cost antenna prototype has a fully directional radiation pattern with measured gain up to 12.2 dBi and estimated radiation efficiency of 89%, respectively. A brass plate with 0.8 mm thickness has been fabricated to attach to the antenna ground plane for improving FTBR of more than 30 dB. All these features make the proposed antenna array have good potential applications in X-band system, especially in 9.65\,GHz Airborne SAR systems. The aperture of the antenna is 80 mm x 50 mm, which equals 31 wavelengths at 9.65 GHz.
In order to solve the problem of strong coupling between torque and suspension force of bearingless switching motor and the strong chattering of sliding mode control, a direct suspension force control method for hybrid stator bearingless switched reluctance motor based on 1uasi-continuous third-order sliding mode is proposed. According to the special structure of hybrid stator bearingless switched reluctance motor, the direct decoupling of torque and suspension force is realized. The suspension force control system adopts the direct suspension force control of the third-order sliding mode. By comparing with the second-order sliding mode control system under the condition of interference source and non-interference source, the results show that the designed control strategy has high precision, strong robustness, fast convergence speed, and it can effectively decrease vibration.
In order to improve the efficiency of the quasi-optical mode converter, two methods to design mirror systems for a 170 GHz gyrotron operating in TE32,9 mode are presented in this paper. The first method is to use Katsenelenbaum-Semenov Algorithm (KSA) to design the structure of the mirror. The second method to design the mirror system depends on the phase difference on the mirrors, so we name it PD method. The mirror system consists of three mirrors, and the mirror center position and mirror size are the same for both methods. For the first method, the scalar and vector correlation coefficients obtained at the window are 99.45% and 98.12%, respectively, and the mirror system has been designed with a transmission efficiency of 97.25%. The scalar and vector correlation coefficients and mirror system transmission efficiency are 99.73%, 98.85%, and 97.67% respectively for the second method. Simulation results of the two methods are compared and analyzed, which provide a reference for the design of gyrotron quasi-optical mode converter mirror system.
Artificial noise (AN) aided method in mmWave is hard to realize due to large transmit antennas and also requires additional power. This paper proposes coding matrix secure transmission based on quadrature spatial modulation (QSM) utilizing a frequency modulated diverse retrospective array (FMD-RDA). Specifically, we adopt coding matrix for frequency increment with QSM symbols to form part of FMD-RDA angular-range array factor. Consequently, low probability of detection (LPD) is created during the QSM transmission without additional power. The desired receiver should know the particular coding matrix a priori. Importantly, the system has automatic user tracking ability with no channel state information (CSI) needed at the desired receiver and can handle receivers with highly correlated channels. Further, secrecy outage probability (SOP), asymptotic lower bound on eavesdropper's (Eve's) detecting error probability and average data leakage rate are analyzed without Eve's CSI. Simulation results show that increasing the coding matrix, satisfactory secrecy is attained for the proposed scheme. Moreover, through the results certain essential secrecy information has been highlighted that is not captured by the classical SOP making the proposed scheme an attractive technique for QSM applications.
In this paper, a spectral domain implementation of the fast multipole method is presented. It is shown that the aggregation, translation, and disaggregation stages of the fast multipole method (FMM) can be performed using spectral domain (SD) analysis. The spectral domain fast multipole method (SD-FMM) has the advantage of eliminating the near field/far field classification used in conventional FMM formulation. The goal of this study is to investigate the similarities and differences between the spectral domain analysis and conventional FMM formulation. The benefit of the spectral domain analysis such as transforming the convolutional form of the Green's function to a multiplicative form is incorporated in the SD-FMM method. The study focuses on the application of SD-FMM to one-, two-, and three-dimensional electric field integral equation (EFIE). The cases of perfectly electric conducting (PEC) strips, circular perfectly conducting cylinders, and perfectly conductor spheres are analyzed. The results from the SD-FMM method are compared with the results from the conventional FMM and the direct application of Method of Moments (MoM). The SD-FMM results agree well with results from the direct application of MoM.
In this paper, a monolayer metasurface that can simultaneously generate multi-mode vortex waves in ultra-wideband is proposed. Smooth phase variation is obtained by properly assigning the arm lengths of arrow-shaped metal on the top of the reflective metasurface unit cell. Different reflective cells are arranged in different sectors to form a phase-shifted surface that can convert a linearly polarized plane wave into a vortex wave. The full-wave simulations show that the designed reflective metasurface can generate vortex wave with multi-mode in ultra-wideband from 18 GHz to 42 GHz, which is in good agreement with the theoretical analysis. The proposed reflective metasurface paves an effective approach to generate vortex wave with multi-mode in ultra-wideband for OAM-based systems. Compared to the traditional ways of generating vortex waves, our design has the advantage of wide bandwidth.
In this paper, magnetic fluids based on iron oxide Fe3O4 and 5BDSR alloy were obtained. Magnetic particles were obtained by nanosecond pulsed laser ablation. The preparation of the magnetic fluid was carried out by mechanical and ultrasonic stirring in a solution of polymethylphenylsiloxane. It is shown that under the influence of an external magnetic field, the spectral properties of the magnetic fluid of the 5BDSR alloy correspond to characteristics that can be used to create a magnetic gate.
In this paper, a compact reconfigurable tri-band bandstop filter (BSF) with sharp-rejection and high selectivity is presented. The proposed filter is based on a 50\,Ohms microstrip feed line, six hexagonal metamaterial cells (HMCs) with different sizes and switches. The structure of the filter has seven different modes of operation characterized. A good agreement between the simulated and measured results is obtained. The results indicate that the proposed filter design, with overall size of 0.28λgx0.17λg, is a good candidate for multiservice radios applications.
In this paper, the detection of through the wall multiple human subjects is proposed using the Doppler radar with the help of Hilbert vibrational decomposition (HVD). The proposed Doppler radar can detect the multiple human subjects behind the wall by respiration rate estimation of human subjects. With different breathing conditions resembling to the real life scenario, the respiration signals of human subjects are extracted. The algorithm works in every real life situation to detect the respiration rate of human subjects and finds application in the earthquakes, building collapses and security applications.
This work involves designing an antenna that meets the requirements of radar systems. The associated technology, which was for a long time reserved for the military field, is now available in the civil field, as well as in the biomedical sector for the development of ``monitoring'' systems allowing to monitor the state of health of a patient in a non-invasive way. The goal of this article is to design a wearable textile antenna to detect cancerous tumors of a patient without direct contact with the skin, taking into account the electromagnetic waves directed towards the human body due to the difference between the dielectric constants of healthy and unhealthy tissues. Here we present a miniature AMC antenna of rectangular shape that satisfies the UWB characteristics in terms of bandwidth and reflection coefficient. The proposed AMC antenna operates in X-frequency band, (8-12 GHz). Using a model of dielectric artificial skin, we have simulated the specific absorption rate on the human body in order to better respect the FCC standards allowed 1.6 W/kg averaged to 1g of human tissue.
In view of the dynamic wireless energy charging of electric vehicles, because of the different types or dynamic changes of carrying capacity, the distance between receiving coil at the chassis of electric vehicles and transmitting coil under the road will change dynamically. The unsuitable distance may make the system keep an under-coupling state and reduce the output power of energy transmission system. To improve the system output power, and a relay coil can be added between transmitting coil and receiving coil. But the system charging state may change from under-coupling state to over-coupling state directly because of the introduction of relay coil, and at the same time, the system may show frequency splitting phenomenon. These problems can be solved by adjusting the position of relay coil, the rotating angle of relay coil, and the load value. The experiment shows that the system output power can be improved obviously by increasing relay coil and suppressing frequency splitting. In order to obtain the optimal parameters about the position, rotation angle of relay coil, and load resistance, a genetic algorithm is introduced to improve the output power. At last, using the optimal system parameters, a magnetic coupling resonant wireless power transmission (MCRWPT) system is designed and manufactured, by which the effectiveness and advantage of this approach are verified by experiments.
We present an extension of Large Time Step (LTS) method to electromagnetic wave propagation involving multilayered homogeneous media. The LTS method proposed by LeVeque is an extension of Godunov's method for the numerical solution of hyperbolic conservation laws. In this method, very large time steps are allowed by an increase in the numerical domain of dependence compared to conventional explicit methods constrained by the Courant-Friedrichs-Lewy stability criteria. This can lead to additional complexities when being applied to multilayered homogeneous media due to presence of material interfaces. Appropriate treatment of material interface boundaries is proposed in the present work in the context of finite volume time-domain method with LTS. Numerical examples are presented involving solution of time-domain Maxwell's equations in a layered dielectric medium using LTS approach.
This paper presents the design of an ultra-wideband (UWB) antipodal Vivaldi antenna (APVA) for radar and microwave imaging applications. A slotted APVA design is introduced to improve the low-end bandwidth limitation frequencies as well as to enhance the gain and directivity of the antenna. The optimizations of the design offer good results by using a cost-effective substrate, fiberglass reinforced grade 4 (FR4) material. The regular APVA antenna design only presents average results of gain (4-6 dBi) and directivity (4-7 dB). However, the addition of slots on the edges of antenna is able to increase the peak value of gain and directivity up to 73.65% with 7.64 dBi and 8.92 dB, respectively. Besides, the radiation pattern of the antenna is also improved by using the slotted design where the main lobe level is larger than regular APVA design. Both antennas presented in this paper are designed in compact size of 42.8 mm x 57.3 mm. The antennas are also designed to operate within the frequency range of 3.6 GHz to 10 GHz frequency.
With the progress of technologies though the years, the extent of electromagnetic radiations has increased in our environment, so there are increased concerns about health for wireless device users. It has become a necessity to use devices with low Specific Absorption Rate (SAR) to reduce human exposure to the effects of Electromagnetic Fields (EM fields). In this article, the design of a circular microstrip antenna (CMSA) with and without an electromagnetic band gap (EBG) structure is proposed. It is evident from simulated results that CMSA with EBG gives low SAR as compared to CMSA without EBG for the proposed prototype. M-shaped unit cell structure of EBG is designed for 1812 MHz resonance frequency, and a bandwidth of 244 MHz is achieved using CMSA with EBG for LTE Band 3. SAR is reduced by 76.25% when CMSA is used with EBG in comparison to CMSA without EBG.
GBSAR has been widely used in landslides monitoring for its high precision in deformation monitoring and portable characteristic in natural environments. When monitor slides in mountainous areas, GBSAR cannot only work in positive mode, and its antennas may be directed to the target with a large squint angle. Unfortunately, normal range doppler imaging algorithm is not used well in such applications. Thus, a correction method of RD algorithm for SAR imaging with a squint angle has been proposed in the paper. Because the monitoring target may be far away from the view center of the GBSAR, echo of the target may be side lobe resided, when it is received by the radar's sensor. Simultaneously, distance between the sensor and imaging target changes with the azimuth time. Therefore, target in the SAR image would not be focused in one range bin if no range correction method was used. Thus, phase correction methods were used in the paper. The phase error was corrected in range domain and azimuth domain, respectively. It avoids 2D FFT processing. Thus, it may use few time and work. In this way, the GBSAR would have real time processing ability in the future. In the paper, a GBSAR was designed and used in slide monitoring applications in western mountains of Beijing. The experiment result shows that the system can measure target's micro deformation in mm levels with a high precision.
In this paper, a novel high-gain repeater antenna integrating a dual-feed network is proposed to receive and transmit RF signals separately by two ports. The proposed array antenna has four linearly polarized microstrip antenna elements, two feed networks, and one planar magic-T. The distance between the elements of the array antenna is matched to obtain the minimum sidelobe level and maximum half-power beamwidth for transmitting and receiving purpose. The planar magic-T is effectively used to meet two different bi-directional radiation patterns with a simple structure. Performances of the array antenna are experimentally confirmed, and the gain of the antenna for each port is better than 10.3 dBi. The measured 10-dB impedance bandwidth of the antenna is wider than 580 MHz (10%).