A compact ultra-wideband antenna is presented for detecting malignant cells in the breast. The dimension of the proposed circular resonator-based antenna is 20 mm x 30 mm x 1.6 mm. The antenna sensor operates within the 3.1 GHz to 6.8 GHz (105.71%) range with peak gain 4.8 dB, radiation efficiency 89.2%, and an omnidirectional radiation pattern. Three types of breast phantoms (i.e., phantom without tumor, a phantom with a single tumor, and phantom with two tumors) arealso fabricated. The electrical properties of the malignant cells differ from non-malignant breast cells. S-parameters have been measured with phantom, then with the help of Principal Component Analysis (PCA), and normal and malignant breast phantoms are identified. Further, the tumor's locations in the breast phantom are find out by using the specific absorption rate (SAR) values.
In this work we present near-field image transmission and error vector magnitude measurement in rich scattering environment in metal enclosure. We check the effect of loading metal enclosure on the performance of SDR based near-field communication link. We focus on the key communication receiver parameters to observe the effect of near-field link in presence of rich-scattering and in presence of loading with RF absorber cones. The near-field performance is measured by transmitting wideband OFDM-modulated packets containing image information. Our finding suggests that the performance of OFDM based wideband near-field communication improves when metal enclosure is loaded with RF absorbers. Near-field EVM improves when the enclosure is loaded with RF absorber cones. Loading of the metal enclosure has the effect of increased coherence bandwidth. Frequency selectivity was observed in an empty enclosure which suggests coherence bandwidth less than the signal bandwidth.
The direct control for the bearingless permanent magnet synchronous motor (BPMSM) has problems of large ripples of flux linkage, torque, and suspension force due to sampling time delay. To solve above problems, a predictive direct control method is proposed based on the traditional direct control by adding prediction model. Firstly, the generation principle of radial suspension forces of the BPMSM is introduced. Secondly, the models of the predictive direct control method are given based on the traditional direct control, and the time-delay compensation model is deduced. Thirdly, the predictive direct control system is constructed, and the simulations are carried out. Finally, the proposed control strategy is applied to a prototype, and the related experimental results are given and analyzed. The results of the simulations and experiments show that compared with the traditional direct control of the BPMSM, the predictive direct control strategy can effectively reduce the ripples of flux linkage, torque, and suspension forces, and improve the static and dynamic performance of the BPMSM.
A new numerical method is proposed for uncertainty quantification in the two-dimensional finite-difference frequency-domain (FDFD) method. The method is based on an intrusive polynomial chaos expansion (PCE) of the Helmholtz equation in terms of the material properties. The resulting PCE-FDFD method is validated against Monte-Carlo simulations for an electromagnetic scattering problem at 1.0 GHz. Good agreement is found between the statistics of the electric fields computed using the proposed method and the Monte-Carlo results, with a factor 15-120 reduction in the computational costs. The PCE-FDFD method is also applied to estimate the material properties from exterior measurements by formulating an objective function and applying constrained optimisation techniques. A maximum 1.7% error in the material properties was observed for a test geometry with six unknowns and 20 sample points.
The method of evaluating the resonant frequencies of a multilayered cylindrical resonator containing uniaxial anisotropic materials is presented. The detailed solution of Maxwell's equations for such a structure by means of the radial mode matching method is given. The results of calculations using developed and launched computer program are given, and they are compared with those obtained by other methods and with measurements. These results are in close agreement, which proves the correctness of the method. The developed solution and the software program can be used to measure the permittivity tensor of materials.
The traditional electromagnetic wave wireless communication in the underground environment has the problem of unstable channel path loss, large antenna size, high path loss, etc. To address these issues, the channel models of magnetic induction communication and magnetic induction waveguide communication based on quasi-static field coupling are proposed, and the characteristics of magnetic field strength, path loss, bandwidth, and channel capacity are analyzed in detail. The results show that the magnetic induction communication system channel is stable, compared with the ordinary induction communication, and the path loss of magnetic induction waveguide communication is reduced a lot, even in the case of high noise and transmission distance increased by more than 20 times. But the bandwidths of the two ways are small and similar. The path loss and bandwidth decide the system capacity, and system capacity is also affected by the number of turns, working frequency, coil resistance, and size.
The suppression of crosstalk by combining the defected microstrip structure (DMS) with step-shaped transmission lines is proposed to address the problem of crosstalk between microstrip lines of the printed circuit board. This method suppresses the crosstalk between the microstrip lines by constructing two step-shaped coupled microstrip lines and etching the designed G-shaped DMS on one of the microstrip lines. Simulation and actual measurement results show that the combination of G-shaped DMS and step-shaped transmission line can effectively suppress crosstalk and reduce the far-end crosstalk by approximately 20 dB in the frequency range of 4-5 GHz. The actual measurement results in the vector network analyzer coincide with the high-frequency structure simulator simulation results.
This paper presents a recent progress in a millimeter-wave imaging done with a potential 5G base-station phased-array antenna exhibiting frequency-diverse, non-focused beams. The presented imaging system operates in 24-32 GHz band and is the first realization where phased arrays primarily developed for 5G communications are utilized in a frequency-diverse imaging application. The image reconstruction method solves the linear inverse problem with an iterative algorithm, and several images have been reconstructed based on the measurement data. Currently, a metallic sphere can be successfully located in the target space. However, future work is still required, and the paper further discusses the possibilities and restrictions of the current imaging setup.
Due to the nonuniform Electromagnetic (EM) field distribution over the superstrate, a Fabry-Perot Resonant Antenna is normally with high directivity but relatively low aperture efficiency when its aperture size is electrically large. In this paper, a Fabry-Perot resonator cavity antenna (FPCA) with a nonuniform metamaterial superstrate is proposed. The nonuniform metamaterial superstrate is a nonuniform double-sided printed dielectric, in which the upper surface is used for wideband RCS reduction, and the bottom surface is the nonuniform partially reflective surface (PRS) of FPRA for wideband and high aperture efficiency performances. Wideband RCS reduction is realized by designing the phase differences 90˚ in turn among three adjacent frequency-selective surfaces. The wideband 3 dB gain bandwidth and high aperture efficiency performances are obtained by designing the PRS with a positive reflection phase gradient vs frequency and a negative transverse-reflection magnitude gradient, respectively. The measured results show that the gain of the proposed antenna is 11.5 dBi greater than that of the primary source antenna with a peak value 15.5 dBi at 9.2 GHz. The aperture efficiency is 73.3%. The 3-dB gain bandwidth is from 8.75 to 11.47 GHz (26.9%), and the RCS reduction can be obtained effectively from 8.2 to 20 GHz (83.7%).
We present experiments of contact electrocardiograms (ECG) recording using copper and e-textile-based flexible dry electrodes. In this work, dry electrodes with different shapes, sizes, and materials were designed and fabricated. In cardiac monitoring using these flexible dry electrodes, three different conditions were considered, which are sitting, standing, and walking. To evaluate the performances of the fabricated dry electrodes, average-to-variation ratios (AVR) of the recorded ECG signals measured using the flexible dry electrodes were calculated and compared with those measured using the commercially-available wet electrodes in all three conditions. The AVR results demonstrate that the dry electrodes have a similar performance as the commercially-available wet electrodes in the sitting and standing conditions and a better performance in the walking condition. These results suggest that it is possible to weave dry e-textile-based electrodes in normal clothing and use them for continuous monitoring of ECG signals in different conditions.
In this paper, we propose a laser monitor with a horizontally located observation area for studying laser initiation and combustion of thin layers of metal nanopowders. Three configurations of the optical scheme with different inputs of igniting laser radiation and different magnifications are considered. Visualization of combustion of a 0.4 mm layer of aluminum nanopowder demonstrated the possibility of studying the surface of a nanopowder thin layer during combustion using a laser monitor. The bright glowing of the sample and the bright radiation of the igniting laser do not interfere with the imaging of the surface. The proposed system allows us to study surface changes caused by the propagation of combustion waves. It is demonstrated that in the region of laser initiation, combustion proceeds in one-stage, and combustion products are formed during laser action. Outside the initiation area, combustion proceeds in two stages. The results reveal the prospects for designing a laser monitor for studying the combustion of thinner layers of metal nanopowders.
A band-pass filter using spoof surface plasmon polaritons (SSPPs) and half-mode substrate integrated waveguide (HMSIW) for Ka-band RADAR application is proposed. In order to achieve the band-pass response, an HMSIW structure with high pass response and SSPPs with band-stop response are combined. Moreover, to investigate effects of geometric dimensions on the frequency characteristics of the proposed band-pass filter are examined by parametric analysis. It has been observed that lower cut-off and upper frequencies can be individually controlled just by changing the structural parameters. High Frequency Structure Simulator (HFSS) software was utilized to simulate the proposed structure. HFSS is the simulation tool for complex 3-D geometries and uses the finite element method (FEM). To validate the functionality, the proposed band-pass filter is fabricated on the dielectric material RT duroid 5880 with the dielectric constant εr = 2.2, height h = 0.508 mm, and dissipation factor tanδ = 4 × 10-4. The measured result shows return loss better than -10 dB and insertion loss less than 1.25 dB with the 3 dB fractional bandwidth (FBW) of 44.02% at the center frequency of 7.95 GHz.
In a wireless magnetic induction communication system, the magnetic field distribution of the current-carrying coil affects the communication effect between the communication transceiver and receiver. In the study of magnetic field distribution, it was found that magnetic induction intensity and magnetic flux were important parameters to measure the effectiveness of communication. Aiming at the circular coils with rectangular cross-section of any turn numbers, this paper proposed an improved algorithm to calculate the magnetic induction intensity at any spatial position based on Biot-Savart law. At the same time, the calculation formula of the magnetic flux at the receiving point was also given. The coils were modeled and simulated with COMSOL software. The correctness of the improved algorithm was verified and compared with the traditional formula and simulation results, especially in the near field, which provided an important theoretical support for the further study of mutual inductance in the wireless magnetic induction communication system.
For replication concerns, this paper describes the work of the LAPLACE Electromagnetism Research Group to build NASA-like cavities in order to exploit the same electromagnetic configuration: the same resonant mode. These cavities are then implemented in our straightforward EMDrive experimental setup with a 0.1 mN sensitivity. Force measurement protocol is presented and discussed while more than 150 W of RF power is injected into the cavities. Results are compared to the NASA stated thrust to power ratio of 1.2±0.1 mN/kW.