Recent advancement in ultra-low-power electronics and radio communications has significantly contributed to the development of miniaturized biomedical sensors capable of capturing and transmitting wirelessly physiological data. The characterization of signal and power transmission inside the human body is of great importance. This paper investigates the case of an intra-body wireless communication in the UHF frequency band. An implanted antenna (bent dipole) is designed to operate efficiently in a biological tissue model. Predictions of the performances obtained by 3D electromagnetic simulations are compared to measurements in a realistic environment (pork meat in a box of 18x10x7 cm3). The antennas show return loss matching of -12 dB at 1,2 GHz, in the presence of the meat. Then a characterization of the transmission link between two antennas is performed both numerically and experimentally at 1,2 GHz. At this frequency, the measured |S21|2 is around -35 dB at 6 cm, and -40 dB at 8 cm. The simulation of the |S21|2 highlights the impact of the conductivity of the tissues, driving to values of -25 to -55 dB at 6 cm, and -30 to -65 dB at 8 cm. The characterization of the pork meat is evaluated experimentally around 2 S/m. During the process of characterization, this value may be over-estimated due to the pressure applied on the sample. The simulations results are compared with measurements results, and also with retro-simulations results. The latter are considered as a worst case due to the losses implied by the over-estimated conductivity value.
In this paper, a microstrip sensor based on a complementary split ring resonator (CSRR)-derived structure is proposed to characterize the permittivity and permeability of materials. By loading an etched meandered conductive ring and an interdigital capacitor structure, effective separation of the permittivity sensing area and permeability sensing area is realized, and the field strengths of the corresponding areas are improved. The relationship between the resonant response (resonant frequency and quality factor) of the sensor and the permittivity and permeability of the sample under test (SUT) is discussed, and the theoretical basis for measuring the material properties is given. By analyzing the measured resonant frequency and quality factor, the real and imaginary parts of the permittivity and permeability of the SUT can be determined. The sensor was fabricated on a Rogers 5880 substrate, and four standard dielectric and magnetodielectric (MD) samples were tested. The results show that the measured values of the real and imaginary parts of the permittivity and permeability are in good agreement with the reference data.
In order to realize the maximum torque output (MTO) in the field-weakening region for the bearingless induction motor (BIM) stator vector control, a flux feedforward control strategy was proposed. Firstly, based on the restrictions of the stator flux oriented control and the dynamic characteristics of the current in the BIM field-weakening region, the optimal distribution of the torque current and the excitation current and the dynamic model of the maximum torque output strategy are analyzed. Then the field-weakening region could be divided into two parts according to the change of slip, it can be proved that the BIM works under the voltage and current limitations in the field-weakening region I, and works under the voltage and torque limitations in the field-weakening region II. By this way, the optimal flux mathematical model of the motor can be obtained. Finally, the maximum torque output in the field-weakening region is proved. The simulation and experiment results show that the proposed flux feedforward control strategy in the field-weakening region can make the output torque and current tracking effect improve significantly when the BIM runs beyond the rated speed. At the same time, the suspended rotor has good suspension performance, and high efficiency and stability of the BIM is realized.
A novel active metasurface which is switchable to accomplish dual band gain enhancement is reported. The metasurface is used as a superstrate above the dual band patch antenna working at 2.4 GHz and 4.6 GHz. The gain of the antenna is enhanced by 3.5 dB at both frequencies. Switching between the frequencies is enabled by a p-i-n diode. When the p-i-n diode is in OFF state, gain is enhanced at 2.4 GHz, while gain is reduced at 4.6 GHz and when the p-i-n diode is in ON state, gain is enhanced at 4.6 GHz, but reduced at 2.4 GHz. The diode is controlled by biasing with a regulated DC source. The efficiency of the antenna is 70% at 2.4 GHz and 85% at 4.6 GHz. The simulated and measured results show good agreement. The distance between the antenna and the superstrate is 6 mm, which is 0.048λ at 2.4 GHz and 0.092λ at 4.6 GHz. This superstrate can be used in WLAN and Sub-6 GHz 5G applications.
A novel low-profile GNSS microstrip circular polarization antenna is proposed and analyzed. Circular polarization is realized by asymmetric structure patch, and arc structure loaded on the main radiator can keep two modes orthogonal over a wide-angle range, so that the antenna has an extremely wide 3 dB axial ratio beamwidth (ARBW). The far-field AR beamwidths obtained are 232° and 212° respectively in the main plane of φ=0° and φ=90°. In φ=45° and φ=135°, 3 dB AR beamwidths are 241° and 244°, far exceeding the 120° required for satellite applications. In the whole CP band, 78.95% of the beam width exceeds 180°. The profile is only 0.0156λ0, which is suitable, especially, for portable wireless systems or devices. The return loss bandwidth of -10 dB is 5.13% (1.52 GHz-1.6 GHz), which covers BeiDou Navigation System B1 (1.561 GHz). The axial ratio bandwidth is 1.28% (1.55 GHz-1.57 GHz), and the in-band peak gain is 4.09 dBi.
This paper presents a highly directive pattern reconfigurable antenna array capable of switching single or multiple beams of high directivity in multiple directions. Each element is individually capable of providing radiation pattern of directivity 12 dB and realized gain of 10.2 dB. Here, eight directive array elements are arranged in a circular fashion resembling a fan along with a switching arrangement to obtain beam switching in the horizontal plane. Two or more elements can be excited simultaneously to obtain patterns in multiple directions. In another configuration, the elements are arranged around a cylindrical support resembling an umbrella structure to obtain azimuthal switching at a desired tilt. The ability to reconfigure patterns in desired direction facilitates their usage as base station antennas providing desired angular coverage to intended users only, resulting in least signal interference.
A novel mid-infrared (MIR) biochemistry sensor using two suspended GaAs waveguides based on an asymmetric Mach-Zender Interferometer (MZI) is proposed. The propagation properties and refractive index (RI) sensing performances of MZI are investigated by the finite element method (FEM). The simulation results show that the maximum waveguide sensitivities (Swg) of the TE and TM modes in the suspended GaAs waveguide are ~1.2 and ~1.0. This design of the GaAs waveguide using the suspension structure is to enhance the interaction between the vanishing field and the measured material. The RI sensitivity of the asymmetric MZI structure increases with the length of the sensing arm, which can reach 854.5 nm/RIU with a Q of 208.2 after parameter optimization. The two arms of the MZI are designed as width-asymmetric structures to make the sensor more sensitive to the measured material. The asymmetric MZI sensing structure has high RI sensitivity and compact structure, which provides a feasible scheme for biochemical sensing.
The article presents a compact size and high isolation with 2×2 MIMO, double flare horn shaped antenna for K and Ka bands of mm-wave applications. The overall size of the MIMO antenna 0.19λ×0.19λ×0.01λ mm3 at a lower frequency has been designed, simulated, fabricated and tested. The proposed MIMO antenna components are arranged parallel with identical shaped to provide a high level of inter-element isolation and 50 W micro strip line feed. The antenna covers 18.61-20.01 GHz in the K-band (18-26.5 GHz) and 21.52-33.91 GHz in the Ka-band (26.5-40 GHz) with impedance bandwidths of 7.2% and 44.5% respectively at port-1 and port-2. Maximum peak gain of 6.5 dBi & 8.1 dBi respectively at port-1 and 6.5 dBi&7.9 dBi at port-2 is observed respectively. Diversity characteristics such as envelope correlation coefficient, diversity gain, total active reflection coefficient and channel capacity loss are determined to validate the considered MIMO antenna's work qualities. The isolation of more than 35 dB indicates that the proposed structure is suitable to use a dual-port MIMO antenna. The recommended structure's investigation revealed a steady performance and a high degree of agreement between simulated and measured findings.
This article presents a dipole antenna using an I-shapes adding technique on both sides of the antenna's body. To increase the using frequency range to be wider, with horn waveguide for gain enhancement and harvest energy by matching circuit. Which is compatible with the voltage multiplier circuit at RF frequency (510-790 MHz) in a TV digital system. When taken to measure the effect of the antenna, it was found that the antenna operates at a frequency range of 60.24% (450-838 MHz), a 67.79% increase from the base dipole antenna, which has the gain enhancement of 10.23 dB from adding the horn waveguide 60.99%. By has a pattern of energy radiating in a specific direction, and when the antenna is used with an energy harvesting circuit to get energy or power from the front direction of the TV digital antenna at a distance of 10 km, capable of harvesting energy up to 7.33 uW.
Graphene has become one of the most essential materials in recent years due to its numerous advantages and benefits. Because of its features, graphene is becoming more widespread in a variety of applications, particularly in electrical devices. In this research, graphene thick film paste (GTP) has been used to fabricate a microstrip bandpass filter (BPF). To obtain graphene nanoparticle powder, graphene oxide (GO) was synthesized from nanoparticle graphite using the Improved Hummers Method (IHM). The graphene oxide (GO) was chemically reduced to reduced graphene oxide or graphene (rGO) using ascorbic acid as the reducing agent. The structural and morphological properties of three nanoparticle powders, G, GO, and rGO, were investigated. An X-ray Diffractometer (XRD) (Rigaku Miniflex) with a diffraction angle of 10˚ to 60˚ was used to differentiate and determine the structure of crystalline materials. Thermal stability of the samples was identified using thermogravimetric analysis (TGA). The synthesized rGO has been used to fabricate BPF circuit. The obtained nanoparticle rGO was mixed with an organic carrier composed of linseed oil, m-xylene, and α-terpineol to form GTP. The GTP was screen printed on RT duroid 5880 substrates to form BPF circuit. The BPF circuit that was created was tested for paste-to-substrate adhesion. Then, the fabricated BPF circuit was tested using vector network analyzer (VNA) and compared with conventional BPF to obtaine scattering parameter results which include return loss, insertion loss, and bandwidth. The graphene BPF circuit demonstrated a good performance with return loss and insertion loss at -27.481 dB and -0.725 dB, respectively, and a bandwidth of 1.5916 GHz while conventional return loss was -26.750 dB and insertion loss value the same as graphene which is -0.725 dB and bandwidth 0.7077 GHz. From the result graphene BPF showed better result than conventional BPF.
In this paper, the transport characteristics of gold/silver mixed chain nanostructures with different proportions of infinite length in the range of 270-810 nm are studied, and the corresponding band gap characteristics and other transport characteristics are analyzed. We introduced an analytical model to determine the complex dielectric constant of an arbitrary composition Au-Ag alloy, and combined this with the experimental data to study the propagation characteristics of the infinite-length gold-silver mixed-chain nanostructures with various compositions. As the gold content exceeds Au:Ag(1:2), the coupling coefficient between the forward and reverse waves becomes smaller, and the reverse wave cannot provide enough energy to transfer to the forward wave. The scattering ability of the scattering unit weakens, the frequency range of the propagation state widens, and it exhibits good propagation characteristics. By gradually increasing the proportion of metal in the alloy, we can explore the variation of the propagation characteristics of the alloy. At present, the change of metal propagation characteristics has not been studied from this point at home and abroad, so we found for the first time that frequency modulation can be realized through this method (regulating the attenuation or cutoff frequency range, namely the band gap range). We also studied a cylindrical finite array chain composed of 40 nanorods under five types of experimental data and discussed the wave guiding ability of the finite array chain under the excitation of a plane wave of a specific wavelength.
Aiming at the problem of excessive torque ripple of switched reluctance motor (SRM), a three-interval PWM duty cycle adaptive control strategy is proposed in this paper. The method changes the PWM duty cycle to adjust the voltage across the windings according to the torque error, divides the interval according to the inductance linear model, and adapts to different PWM duty cycles in different intervals, different speeds, and different torque errors. And the optimal PWM duty cycle group under different rotation speeds is obtained by trial and error, and this duty cycle group is used as the control method to adapt the PWM duty cycle group. Finally, through Matlab/Simulink simulation and motor platform experiments, the three-interval fixed PWM duty cycle control strategy and the three-interval PWM duty cycle adaptive control strategy in this paper are compared. The results show that the three-interval PWM duty cycle adaptive control strategy proposed in this paper has a good torque ripple suppression effect in a wide speed and wide load range.
In this paper, a dual-band ultra-wideband conformal antenna for Wireless Capsule Endoscopy is proposed. The antenna uses polyimide as a substrate of side wall to achieve conformality, leaving space for other components of the Wireless Capsule Endoscopy. The feeding network of the conformal antenna utilizes the circuit characteristics of Complementary Split-Ring Resonator to achieve dual-band operation at 1.4 GHz and 4.0 GHz. Based on the principle of wideband characteristics of spiral antennas, the conformal antenna radiation structure is improved. A short-pin is loaded at an appropriate position to improve the impedance matching of the antenna and achieve ultra-wideband without changing the resonant points of the antenna. The operating bandwidth of the antenna can reach 30.3% (1.20~1.63 GHz) and 53.3% (3.33~5.75 GHz), respectively. In addition, the antenna is placed in different simulation models to verify the stability of its operation. Minced pork is used to verify effectiveness of the conformal antenna. The measured results show that the proposed antenna is suitable for capsule endoscopy.
Multi-carrier Phase Coded (MCPC) signal has the advantages of large time-bandwidth product, low intercept, anti-jamming, digitization, flexible waveform, and high spectral utilization, and has become a hotspot in radar waveform research. However, MCPC signal has high-distance sidelobes which are difficult to suppress, after pulse compression processing. Excessive sidelobes will mask the existence of small and weak targets, thus losing the target signal, which limits the practical application of MCPC signals. Therefore, it is of great significance and practical value to study the sidelobe suppression of MCPC signals. From the point of view of waveform design, a multi-carrier phase-encoded signal combining chaotic encoding and single encoding (MCPC-CS) is designed by using chaotic sequence as phase encoding of MCPC signal and optimizing it. In this paper, peak sidelobe level ratio (PSLR) is used as a evaluation factor of the autocorrelation function. The simulation results show that MCPC-CS signal has a good autocorrelation peak sidelobe level ratio, and the autocorrelation sidelobe is reduced by more than 3 dB compared with the normal MCPC signal.
In order to solve the nonlinear couplings among speed and the radial displacement of the outer rotor coreless bearingless permanent magnet synchronous motor (ORC-BPMSM), a decoupling control strategy based on the least square support vector machine (LS-SVM) generalized inverse is proposed. Firstly, the basic structure and working principle of the ORC-BPMSM are introduced, and the mathematical model of torque and suspension forces are established. Secondly, the ORC-BPMSM system is proved reversible by establishing mathematical models and reversibility analysis, then the pseudo-linear subsystems are formed by connecting the generalized inverse system, which is identified by the LS-SVM, with the original system. Furthermore, additional closed-loop controllers are designed to improve the stability and robustness of the pseudolinear subsystems. Finally, the proposed method based on LS-SVM generalized inverse is compared with traditional inverse system method by simulations and experiments. The simulation and experiment results show that the proposed control strategy has good performance of decoupling and stability.
This paper presents a dual-polarized crossed-dipole antenna with high isolation and wide-beam radiation. The antenna comprises two orthogonal printed dipoles with single-ended and differential feeds, which are collocated on a square ground plane. The single-ended feed dipole is built on the peripheral sides of a two-layer substrate, and it is fed by a Г-shaped stripline sandwiched between the substrate layers. The differential-feed dipole is built on a single-layer substrate, i.e., the differential feed with a Π-shaped microstrip-line, and the dipole arms are printed on the top-side and back-side of the substrate, respectively. The high isolation feature is achieved by exploiting the symmetry of the design with one pair of differential feeds. The beamwidth is significantly broadened by incorporating parasitic monopole elements while keeping the design symmetrical. A realization of the design concept for the 5G NR n78 band (3.3-3.8 GHz) has been optimized, fabricated, and tested. The measured results demonstrate an impedance bandwidth of 28.6% (3.0-4.0 GHz) and port-to-port isolation of > 40 dB. Furthermore, the antenna achieves a peak half-power beamwidth of 150°/168° in the E/H planes, and a cross-polarization level of < -30 dB at the broadside direction. These features make the proposed antenna a good candidate for the 5G and in-band full-duplex applications.
In this paper, we propose a quadruple band-notched ultra-wideband (UWB) antenna with a novel virus-mimicking structure. The proposed antenna is fed by coplanar waveguide in the FR4 material. It has a compact size of 27 × 29 × 0.8 mm3. In order to reject narrowband signal interference in ultra-wideband communication, the desired notches in WiMAX (3.3-3.6 GHz), WLAN (5.1-5.8 GHz), downlink X satellite communication system (7.25-7.75 GHz), and ITU 8GHz band (8.025-8.4 GHz) are realized. Except for these, impedance bandwidth of the designed antenna is less than -10 dB from 2.5 GHz to 15 GHz, with average gain of 3 dBi. At the same time, it basically meets the omnidirectional requirement. With low profile and compact structure, the proposed antenna can be integrated into the ultra-wideband system, which can meet the requirements of ultra-wideband communication and improve the anti-interference ability of ultra-wideband communication.
This paper proposes a hybrid excited permanent magnet vernier motor for low-speed and high torque applications in electrical drive. Traditional PM vernier motors are with PM excitation field, and the air-gap magnetic field density is hard to adjust, which limit the wide speed range of PM motor. The hybrid excitation method is proposed in the PM vernier with excitation windings set in the region between modulation pole pieces. With the finite analysis method, the basic structure and the working principle of the proposed motor are introduced, and the low-speed and high-torque characteristics with wide speed range are revealed. Then, the drive control system of the motor is designed and applied with the prototype motor. Finally, the experimental results verify the reliability and effectiveness of the design theory and simulation results.
A small ring antenna working at 2.45 GHz was designed in this paper, a small disk-coupled structure was applied to feed an inner-hole-biased ring patch, contributing to not only improving the impedance characteristics of the antenna but also reducing the size. The simulation results show that the designed patch area is only 70.7% of that of the traditional circular microstrip antenna on the premise of ensuring good bandwidth and gain performance; the -10 dB bandwidth of S11 parameter is 62 MHz; the gain of the maximum direction is 7.11 dB; and the circular polarization of the antenna is also realized. This design has also been compared with several conventional designs, It is proved that the antenna has good comprehensive performance, and the antenna feed structure is simple, easy to process, very conducive to engineering applications. Finally, the feasibility of this technology was verified by contrasting the measured data with the simulation data.
In this work we demonstrate the extended and generalized methodology for the design of Quad-Furcated Profiled Horns (Q-FPHs). Based on a design case of a 4λ0×4λ0 Q-FPH, we extract the Generalized Scattering Matrix (GSM) of the enlarged quad-furcated discontinuity and provide analytical expressions for its multimode feeding. Next, the four feeding and the upper common waveguide sections are optimized accordingly through Mode-Matching (MM). The high aperture efficiency levels delivered by the methodology are verified by full-wave simulations of the optimized design case and compared to the state-of-the-art which is thereby redefined.
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