The fifth generation (5G) wireless communication systems are projected to work at millimeter wave (mm-wave) frequency bands that would bring new challenges with the implementation of antennas and safety level of electromagnetic field exposures. In this paper, a new design of 5G mmwave antenna for multi-frequency bands has been introduced. The antenna is small enough and has a form factor that can be easily fit into the current available mobile handset devices. The proposed antenna covers all the nominated frequency bands by the FCC for 5G communications and has good radiation performances at 28 GHz, 37 GHz, 39 GHz, and 64-71 GHz. The electromagnetic field exposure to the human head model has been studied by means of numerical simulation for all above frequency bands. The feature of our proposed antenna is that all the frequency bands for the 5th generation mobile handset will be available in a single and simple antenna structure; hence, analysis of EMF exposure in a wide range of frequency can be done on a single antenna design.
Partially coherent Lorentz beams have been introduced to describe the output of the diode laser, which have been investigated due to the special spreading properties. The analytical expressions of partially coherent Lorentz beam propagating in oceanic turbulence are derived. Using the derived equations, the average intensity distributions of partially coherent Lorentz beam are analyzed and discussed. It is shown that the partially coherent Lorentz beam with smaller coherence length will evolve into the Gaussian-like beam faster, and the beam propagation in oceanic turbulence will spread faster with increasing strength of oceanic turbulence. The results have potential application in underwater optical communications and sensing.
In this paper, an enhanced characteristic basis function method (ECBFM) is proposed to calculate the monostatic radar cross section (RCS) of electrical large targets efficiently. The enhanced characteristic basis functions (ECBFs) are defined by combining improved primary-characteristic basis functions (IP-CBFs) with the first level improved secondary-characteristic basis functions (IS-CBFs) for each block. IS-CBFs are obtained by substituting IP-CBFs for PCBFs in Foldy-Lax multiple scattering equation in which mutual coupling effects among all blocks can be included systematically. As a result, a small number of incident plane waves (PWs) is sufficient when dealing withlarge scale targets. The numerical results demonstrate that the computational efficiency in this paper is much higher than that of the improved primary-characteristic basis function method (IP-CBFM) without losing any accuracy.
This paper presents a P-OMP-IR algorithm for the hybrid precoding problem in millimeter wave (mm-Wave) multiple-input multiple-output (MIMO) systems. In the proposed approach, the digital precoding matrix is updated via the orthogonal matching pursuit (OMP) method, and the analog precoding matrix is refined column by column using the dominant singular value and corresponding singular vectors of a residual matrix successively. During the refining phase of the analog precoding matrix, an extended power method is designed to calculate the dominant singular value and the corresponding left and right singular vectors, which is able to reduce the computational complexity significantly. Simulation results show that the proposed algorithm can not only reduce the residual of the hybrid precoder effectively, but also improve the spectral efficiency consistently.
In this paper, an ultra-wideband standard transducer based on microstrip line is developed for the accurate measurement and metrology of UWB-SP. The transducer consists of a section of microstrip line and a section of coaxial line connected to microstrip line via an SMA connector. The beginning end of the transducer is chosen to receive the excitation signal, to expand the effective time window. Simulated results show that the waveform recovered by the transducer is almost coincident with the excited electric field waveform within the effective time window, and the upper frequency of the bandwidth is up to 3.5 GHz. The measured results show that the transducer can recover the waveform of the incident electric field very well, the sensitivity and time window can be calibrated readily and accurately by and the vector network analyzer as well as the UWB TEM cell. The experimental results are in agreement with the results from theoretical results and simulated results.
Due to urgent needs for exploring new energy resources, a novel approach is developed in this paper to integrate the functions of a photovoltaic (PV) panel with an ultra-wide band (UWB) antenna array as a unit for collecting solar energy and RF radiation power. The UWB antenna is printed on the front panel of the PV surface. The antenna structure is customized with minimum shadowing effects on the PV surface, by using eight monopoles connected to one SMA port as a single antenna array. Then, to ensure the bandwidth enhancement, each monopole is coupled to three Split Ring Resonators (SRR) structured in a single column as a matching circuit. Next, an experimental study is performed to investigate the amount of the harvested energy from both the PV and the antenna array. The antenna experimental measurements are conducted to realize the I-V characteristics for the PV and produced output voltage and efficiency from the RF radiation power at 900 MHz only. Numerically, the proposed antenna array performance is simulated by CST MWS and HFSS software packages. Finally, the antenna performance in terms of S11 and the radiation pattern at 900 MHz are measured and compared to the simulated results to end up with excellent agreements.
Investigation of backscattering enhancement of waves propagation in random medium is a crucial factor in remote sensing. Medium effects on waves backscattering are important to measure the error rate in radar detection of targets with a finite size. In this paper, we present numerical results for the backscattering enhancement factor assuming different medium parameters and target configuration. Convex illumination region of partially convex surface is assumed. We consider targets to take large sizes of about five wavelengths and a plane wave incidence in the far field. Waves propagation and scattering from objects are calculated in free space and random medium while considering Epolarization of incident wave.
This paper provides the theoretical validation of the unconditional stability, using the Von Neumann method, for the radial point interpolation method (RPIM) and Crank-Nicolson (CN) scheme, in a three dimensional (3D) problem. Moreover, the matrix inversion process, typical of the CN implicit scheme, is circumvented and approximated by a finite series for a particular stability factor range. To validate numerically the efficiency of the CN-RPIM unconditional stability, the resonant frequency inside a 2D double ridged rectangular cavity is simulated. The numerical results confirm that the CN-RPIM is significantly efficient, since the simulation time is reduced by up to 90%, and the memory requirement is saved up to 81%, with a few loss of accuracy.
High power density and torque capability are distinguished features of slotted axial flux permanent magnet machine. However, due to alternate placement of slot and teeth, the airgap permeance and airgap magnetic energy vary with angular position. Even in absence of current excitation, the magnetic variation with position results in cogging torque. This torque produces several undesirable phenomena such as mechanical vibration, acoustic noise, torque ripples, voltage ripples and speed ripple in machine performance. The severity is high for low speed, light load, and direct drive applications. Various design modifications such as slot skewing, magnet skewing, axillary slots, optimization of pole pitch to pole arc ratio and many more are reported for cogging torque mitigation. Any of these design modifications adversely affects the machine performance in terms of no load magnetic field distribution, linkage flux, and induced emf. In this paper, the effect of magnet skewing is investigated for dual-rotor permanent magnet axial flux machine. The analytical model is developed for the determination of magnetic field distribution at no load. Three different types of open slots stators viz. type 1: trapezoidal Slot with trapezoidal teeth, type 2: Parallel slot with trapezoidal teeth, and type 3: trapezoidal slot with parallel teeth are used for the investigation of air-gap magnetic field density and cogging torque produced in machine. The analytically obtained results are compared with finite element analysis (FEA) for the validation.
A low phase noise reflection oscillator using a hexagonal substrate integrated waveguide (SIW) resonator is proposed in this paper. The hexagonal SIW resonator, which can combine flexibility of a rectangular cavity and performance of a circular cavity, is convenient for oscillator design. Since any of the six sides of a hexagonal resonator can be utilized for coupling, the oscillator configuration is flexible and adaptable. A simplified generalised phase noise condition and its optimization approach are proposed for the low-phase noise oscillator design. Furthermore, a 10.4 GHz oscillator prototype was designed, fabricated and measured to validate the proposed optimization approach. The measured results show that this oscillator provides 11.3 dBm output power and possesses low phase noise of -127.2 dBc/Hz at 1 MHz offset from 10.4 GHz carrier frequency, which is suitable for low-cost application in microwave and millimeter-wave band.
This paper presents a comprehensive analysis of a current-mode-logic frequency divider (CML FD) and the theoretical locking range of CML FD. The locking range of the CML divider is proportional to the injection ratio. By adding a resistive load, the locking range of the CML divider is not limited by the Q value of the LC resonant circuit. The minimum input power to drive the divider is achieved when the output frequency is equal to the self-oscillation frequency. To verify the properties of wideband and multi-phase outputs, the ÷4 octet-phase frequency divider based on a two-stage CML FD was implemented using a 0.18 μm CMOS process. It has a locking range of 1 GHz to 8 GHz with a 12.6 mW dc power consumption, and the phase deviation between the octet output signals is less than 4.7°. With an ultra-wide frequency bandwidth and accurate octet outputs, the proposed divider is suitable for multi-phase generator applications.
In this paper, the effect of corrosion on the magnetic behavior of a magnetic material used as a magnetic circuit in the induction machines is studied. With this objective, the magnetic properties of the samples with corrosion and without corrosion were evaluated by the study of hysteresis loops using a homemade vibrating sample magnetometer (VSM). The magnetic parameters extracted from the hysteresis loops such as saturation magnetization, coercive, remanent magnetization, squareness ratio, magnetic permeability, and hysteresis area were analyzed. It was shown that more energy is required to demagnetize the sample with corrosion than the sample without corrosion, and the hysteresis loss in the case of the sample with corrosion is more than the case of the sample without corrosion. These mean that when the corrosion is presented in the magnetic circuits of the induction machine, the hysteresis loss increases, consequentially reducing the machine efficiency.
In this paper, a compact dual-band MIMO antenna for WI-MAX and WLAN applications with improved isolation is proposed. The proposed design consists of two counter facing F shaped monopoles placed closely to each other with edge to edge spacing of 10 mm (0.1167λ0 at 3.5 GHz). Each monopole element operates over 3.5 and 5.8 GHz bands. The isolation over the operating dual bands is achieved by using an elliptical slot and a rectangular parasitic strip. S11 < -10 dB is achieved over 3.2-3.8 GHz and 5.7-6.2 GHz with S12 < -20 dB. The overall dimension of the proposed antenna is 30 × 26 mm2. The proposed antenna has correlation coefficient < 0.03, diversity gain > 9.8 dB with stable radiation pattern over the operating dual bands. The measured results are in good agreement with the simulated ones. The proposed antenna is a suitable candidate for MIMO applications.
As a kind of complex targets, the non-rigid vibration of an aircraft as well as its attitude change and the rotation of its rotating parts will induce complex nonlinear modulation on its echo from low-resolution radars. If these nonlinear modulation features which reflect the physical characteristics of an aircraft target can be extracted effectively, then they are helpful to target classification and recognition. However, the echo translational component and background clutter have a very adverse effect on the extraction of such features. On basis of introducing the ensemble empirical mode decomposition (EEMD) algorithm, the paper firstly performs the decomposition of real recorded aircraft echo data from a low-resolution radar by EEMD and distinguishes the false component, body translational component and micro-motion component by calculating waveform entropy in the Doppler domain. Secondly, it carries out characteristic analysis and feature extraction further on the echo micro-motion component separated and extracts three features of the micro-motion component, including Doppler domain waveform entropy Emc, normalized equivalent Doppler spectrum width BW0, and normalized frequency interval between the adjacent maximum spectral peaks on both sides of the spectrum center Δf0. The analysis results show that EEMD can be used to separate the body translational component and micromotion component of an aircraft echo effectively, and the proposed features (Emc, BW0 and Δf0) can be used as effective features for aircraft target classification and recognition.
The rapid quantification method of human serum glucose was established by using the Fourier transform infrared spectroscopy (FTIR) and attenuated total reflection (ATR). Based on the optimal predicting effect, a subtraction band model combining with optimal single continuous wave band was developed. The spectrum (1600-900 cm-1) was selected as the base band. Then, window subtracted partial least squares (WSPLS) based on the spectrum was carried out, and the optimal two continuous bands were found. The results show that the prediction effect of the base band model is obviously better than that of the whole spectral model, and WSPLS model is even better than base band model. Finally, an independent test set was tested for model verification. V-SEP and V-RP were 0.831 mmol/L and 0.882, respectively by the compensation model.
In this paper, a dual-band antenna in orthogonal polarization with stacked configuration is proposed. The proposed antenna introduces two layers of radiating patches to realize the dual frequency characteristic. A pair of novel 180˚ broadband microstrip baluns, printed on the backside of the bottom substrate, are utilized to feed the antenna. By employing wideband feeding mechanisms for the two input ports, high input port isolation and wide impedance bandwidth are successfully realized. The proposed antenna is fabricated and measured. It exhibits a characteristic of two resonant frequencies, from 2.75 to 4.01 GHz with a relative bandwidth of 37.3% and over 8.1 dBi gain at two ports, and the upper band f2 is from 4.4 to 5.21 GHz with a relative bandwidth of 16.9% and over 5.8 dBi gain at two ports. The port isolation is below -35 dB, and the cross-polarization level is below -20 dB at broadside across the whole band.
The main objective of the current work is to develop a Very Low Frequency (VLF) monitoring system for characterizing low layer ionosphere. Low layer ionosphere is important for communication, and some researchers stressed that lower layer ionosphere can be a precursor to earthquake event. The VLF monitoring system composed of a 1-m antenna, a preamplifier to amplify the signal, an ADC converter and a data acquisition system. The optimization of 1-m antenna received dual frequencies 19.2 kHz and 19.8 kHz from South Vijayanarayanam, India and North West Cape, Australia, respectively. Subsequently, a low pass filter was designed in the preamplifier to pass VLF signals from 0-30 kHz. The results revealed that the system was able to characterize diurnal variation: sunrise and sunset and detect changes in the lower layer ionosphere region due to Solar activity.
Compact size microstrip low-pass filters with sharp cutoff characteristics, narrow passband, low insertion loss, high attenuation in stopband, and low cost are highly required in modern wireless communication systems. They are used to suppress the unwanted harmonics and noise caused by Radio Frequency (RF) front ends. In this paper, a new design for compact microstrip LPF is proposed. It is based on utilization of Stepped Impedance Resonators (SIR), Defected Microstrip Structure (DMS), Dumbbell-shaped Defected Ground Structure (DB-DGS), and surface mount capacitor. The filter is realized on an F4B-2 substrate with εr=2.65, thickness h=0.5 mm and loss tangent δ=0.0013. The design is carried out using CST-Microwave Studio software. The equivalent circuit of the filter is analyzed and presented using ADS2006A software. The filter exhibits sharp cutoff frequency fc=1.7654 GHz, wide stopband from 1.7654 GHz to 7 GHz with |S21| less than -10 dB, insertion loss less than 0.15 dB in passband, and reduced size compared to the traditional LPF.
Inertial properties of the TE-waveguide modal fields are studied in time-domain making use of an analytical method, named as evolutionary approach to electrodynamics (EAE). To achieve inertial characteristics, electric field vector with dimension of volt per meter and magnetic field vector with dimension of ampere per meter in Maxwell's equations are factorized in SI units to obtain new electric and magnetic field vectors with their common dimensions of inverse meter. Having the fields with the common dimensions makes them summable. Using EAE, modal basis elements that depend on transverse coordinates and modal amplitudes that depend on time and longitudinal coordinate are obtained by solving the boundary eigenvalue problem. As a result of using the new electric and magnetic field vectors, the energetic properties are derived as real-valued functions of coordinates and time. Then, the inertial properties (that is, electromagnetic mass and momentum) of the TE-waveguide modes are obtained as the functions of time.
A 3-mm wave interferometer is designed and developed to measure the electron density online at the central chord of Aditya tokamak, unambiguously. The scheme used for this has the advantages in operating the interferometer without a source frequency modulation and easy data processing. The central chord of a 3-mm wave homodyne interferometer system is modified to make a quadrature circuit by using phase shifters and magic tees. This is used to produce the sine/cosine fringe signals. These outputs are amplified and converted into pulses and passed to wired logic up/down fringe counter. Digital synchronous logic circuit is implemented in a Complex Programmable Logic Device (CPLD), followed by digital to analog converter (DAC) and scaler which produces a voltage proportional to increase or decrease in plasma density in real time. The paper presents about this technique and test results of the fringe counter with artificial signals. The chord averaged plasma density ne = 0.9 × 1013 cm-3 is measured online at Aditya tokamak using this interferometer.