Calculating the RCS (Radar Cross Section) of two 3D scatterers needs to numerically solve a set of integral equations involving numerous unknowns. Such a 3D problem can not be solved easily with a conventional Method of Moments (MoM) by using a direct LU inversion. Thus, a hybridization between the Extended Propagation-Inside-Layer Expansion (E-PILE) and the Physical Optics approximation (PO) reduces signicantly the memory requirements and CPU time. The resulting method called E-PILE+PO. In this work, we take advantage of the rank-decient nature of the coupling matrices, corresponding to scatterer 1 (the object) and scatterer 2 (the rough surface) interactions, to further reduce the complexity of the method by using the Adaptive Cross Approximation (ACA).

In this paper, a K-band right hand circularly polarized (RHCP) antenna array with 4×4 elements is designed, fabricated, measured and analyzed. The RHCP pattern is obtained from the helical antenna elements, with a unit cell of every four elements, sequentially counterclockwise by 90 deg. To decrease the profile of the vertical interconnection between the helical antenna and its feeding network, the integration of this RHCP antenna and its feeding networkis realized by low temperature co-fired ceramic (LTCC) technology. The antenna's feeding network consists of eight directional couplers, four circulators, and one power divider. In the feeding network, different RF channels' isolations are improved by the shield structures which are realized by metal filled via holes. For the operating frequency, the measured axial ratio (AR) is better than 1.25 dB. The proposed antenna is small in size, andit is a very good candidate for mobile satellite communications.

The analytical propagation equation of a four-petal Lorentz-Gauss (FPLG) beam propagating through atmospheric turbulence is derived, and the spreading of average intensity is analyzed by using numerical examples. It is found that the FPLG beam propagating through atmospheric turbulence will evolve into Gaussian beam due to the influences of atmospheric turbulence, and the atmospheric turbulence will accelerate the spreading of FPLG beam as the propagation distance increases. It is also found that the FPLG beam with different N or Lorentz widths propagating through atmospheric turbulence will have the same beam spot when the FPLG beam evolves into the Gaussian beam at the same propagation distance.

In the applications such as induction motor efficiency optimization and electric vehicle speed control, the influence of the iron loss cannot be ignored in order to improve the running efficiency of induction motor, the ordinary differential equations (ODE) and difference equations (DE) of induction motors considering iron loss have been established. The results show that the proposed refined ordinary differential equations and difference equations of induction motors considering iron loss and its simulation models are believable, and simulated and experiment results have demonstrated that the models perform well.

The plane wave diffraction by an acute-angled wedge located on a perfect electric conducting plane is studied in the frequency and time domains. Only a TMz polarization is explicitly considered in the manuscript since the case of a TEz polarization can be solved in a similar way. At first, the uniform asymptotic physical optics approach is used to obtain the diffraction coefficients in the framework of the uniform geometrical theory of diffraction. The analytical procedure allows one to obtain closed form expressions that are easy to handle and provide reliable results from the engineering viewpoint. The time domain diffraction coefficients are successively determined by applying the inverse Laplace transform to the frequency domain counterparts. The effectiveness of the proposed solutions is proved by means of numerical tests and comparisons with full-wave numerical techniques.

Recursive convolution FDTD method is employed to study the bistatic radar cross section (RCS) of a conductive plate covered with an inhomogeneous magnetized plasma shroud. The results of numerical simulations reveal that for a plasma of number density 5×10¹⁷ m^-3 and collision frequency of 1 GHz, RCS reduction (RCSR) is improved i.e., its maximum reduction, bandwidth, and angular width are enhanced, when a perpendicular magnetic field of intensity B=0.25 T is applied. However, increase of the magnetic field to 0.4 T leads to a much lower RCSR specially for the backscattered wave. As the collision frequency is increased to 10 GHz, the RCSR is enhanced both in the presence and absence of the magnetic field. However, with further increase of collision frequency to 60 GHz, the RCSR is significantly reduced and the problem is more severe in the backward direction. The resonant absorption is dominant at low to moderate collision frequencies, for magnetic field intensity above 0.1 T, but becomes almost inefficient when the collision frequency is increased to 60 GHz. The RCSR is considerably weakened when the plasma number density is reduced and the effect is prominent for small angles. A plasma inhomogeneity length scale of 5 cm provides the maximum RCSR in the presence of the magnetic field. With increase of the length scale, the maximum RCSR, the corresponding wave frequency, and bandwidth all are reduced. Therefore, it is conclude that a plasma with number density of 5×10¹⁷ m^-3, collision frequency of 10 GHz, and length scale of 5 cm, with a perpendicular magnetic field of 0.25 T is the best choice for optimum RCSR of a conductive plate.

A general theoetical framework for MIMO digital wireless communications is proposed for sending classical M-ary information over quantum states instead of classical electromagnetic waves. The basic theory of quantum MIMO architecture suitable for spatial diversity application is proposed and analyzed. The fundamental design equations are derived and shown to be equivalent to a special constrained nonlinear optimization problem. The main advantage of the MIMO architecture is that it provides new resources for the system designer since using multiple Tx quantum antennas coupled with judicious choice of optimum positions for the multiple Rx quantum measurement operators can enhance the ability to realize quantum communication systems. Therefore, additional degrees of freedom are expected to become available in the proposed quantum MIMO systems. The proposed system is expected to be best physically realized using electromagnetic process in second-quantized (photon) states, ideally coherent or squeezed radiation states.

This paper reports an electric field approximation model of the Coplanar Vivaldi antenna on the E-plane. The study is conducted in three stages, i.e., (i) evaluating the impact of various geometrical parameters to the Vivaldi's element performance at different frequencies, (ii) modeling the electric field patterns, and (iii) applying the model to evaluate the linear total array pattern. The examination of the Coplanar Vivaldi element with fractional bandwidth of 133% in the 2-10 GHz band shows the individual roles of the antenna width, the tapered slot length, the opening width and the slope of the tapered slot in determining the VSWR, resistance, reactance and E-Field performance. The Vivaldi element should be designed with element width more than 0.5λ and less than λ to reach better performance of VSWR and E-field. The longer the tapered slot (>λ) with the high value of opening rate of tapered slot, the smaller the E-field. The E-field increases with increasing opening width of the tapered slot. Knowledge of the influence of each geometry parameter is then used as a reference in developing the E-field pattern approximation model of the Vivaldi element. The derivation of the Vivaldi approximation model is started from the pattern of a horn antenna because both antennas share a similar feature, i.e., the enclosure of the E-field propagation within a tapered slot resulting in a directional radiation pattern. The result of Coplanar Vivaldi modeling is verified against the results of electromagnetic computational simulation and measurement. The Vivaldi element model is useful for total array pattern analysis to save computation time and to provide flexibility in the evaluation of array design.

In this letter, a space time synthesizer for the generation of monthly cloud free line of sight (CFLOS) statistics is presented. The proposed monthly time series generator is based on the synthesis of 3D cloud fields using Stochastic Differential Equations. Monthly Integrated Liquid Water Content (ILWC) statistics are used as inputs, and the temporal and spatial correlation of clouds is considered. The monthly variability of the cloud coverage is predicted, and the CFLOS is estimated taking into account the elevation angle of the slant path and the altitude of the station for high altitude optical ground stations. Finally, CFLOS numerical results are reported, and some significant conclusions are drawn.

In this study, we propose a technique to improve the linearity of complementary metal-oxide semiconductor (CMOS) power amplifiers with a cascode structure. From the investigation of the influence of the impedance of an envelope signal on the linearity, we find that the load impedance of the envelope signal of the common-source transistor should be reduced. To obtain alow load impedance of the envelope signal, we reduce the value of the gate resistor of the common-gate transistor. After investigating the influences of the value of the resistance on the third-order intermodulation distortion (IMD3), we extract the optimum value of the resistance. We also consider the electrostatic discharge protection issue and the effects of the variations in the parasitic components of bond-wires, in the process of the extraction of the optimum value. To verify the feasibility of the optimization technique of the resistance ofthe bias circuit of the common-gate transistor of the amplifier, we design a power amplifier using a 180-nm RFCMOS process for wireless local area network (WLAN) 802.11n applications. We obtain the measured maximum linear output power of 22.2 dBm with a 26.7% power-added efficiency and a 3.72% error vector magnitude. We use an 802.11n modulated signal with 64-QAM (MCS7) at 65 Mb/s. From the measured results, we successfully verify the feasibility of the proposed optimization technique of the resistance of the bias circuit of the common-gate transistor.

In this study, we propose an asymmetrical input transformer for the input baluns in a differential RF CMOS power amplifier to minimize the loss induced by the input transformer. To reduce the loss caused by the magnetic coupling between the primary and secondary parts of a typical transformer, we modify the interconnection between the input transformer and the differential input of the driver stage. Unlike a typical transformer, the primary and secondary parts of the proposed transformer are directly connected to the input of the driver stage. As a result, the input signal in the primary part can reach one of the inputs of the differential driver stage, thereby reducing the loss caused by magnetic coupling. To verify the functionality of the proposed asymmetrical input transformer, we designed a 4.5-GHz differential CMOS power amplifier for IEEE 802.11n WLAN applications with 64-QAM, 9.6 dB PAPR, and a bandwidth of 20 MHz. The designed power amplifier is fabricated using the 180-nm SOI RF CMOS process. The measured maximum linear output power is 17.59 dBm with a gain of 29.23 dB.

The performance of magnetic bearing is determined by its electromagnetic parameters and mechanical parameters. In order to improve the performance of hybrid magnetic bearing (HMB) to better meet the engineering requirements, which needs to be optimized, a multi-objective optimization method based on genetic particle swarm optimization algorithm (GAPSO) is proposed in this paper to solve the problem that the optimization objectives are not coordinated during the optimization design. By introducing the working principle of HMB, a mathematical model of suspension force is established, and its rationality is verified by the finite-element method. By optimization, the suspension force of the HMB is increased by 18.5%, and the volume is reduced by 22%. The optimization results show that the multi-objective optimization algorithm based on GAPSO can effectively improve the performance of HMB.

Solar hydrogen line emission has been observed at the frequency of 1.42 GHz (21 cm wavelength) with 3 m radio telescope installed inside the University of Baghdad campus. Several measurements related to the sun have been conducted and computed from the radio telescope spectrometer. These measurements cover the solar brightness temperature, antenna temperature, solar radio flux, and the antenna gain of the radio telescope. The results demonstrate that the maximum antenna temperature, solar brightness temperature, and solar flux density are found to be 970 K, 49600 K, and 70 SFU respectively. These results show perfect correlation with recent published studies.

A novel, simple and inexpensive microstrip antenna is designed for vehicle communication and specifically for blind spot detection in this work. The proposed antenna is 20.2 mm x 24.1 mm x 1.6 mm in size. Since offset feeding technique is used, manufacturing is simple and cheap. ANSYS Electromagnetics Suite 17.2 simulates the antenna. To suppress mutual coupling, defected ground structure is employed. In addition, the Genetic Algorithm is used to optimize the ground plane width to obtain high gain and omnidirectional characteristics. The simulated results conceive that the `Dedicated Short Range Communication' (DSRC) band band is covered by using the antenna. Moreover, the antenna is fabricated, and the measured results are found to be consistent with the simulated ones.

In this paper, a low-profile, dual-band, unidirectional, tag antennais proposed for ultra-high frequency band (UHF) radio frequency identification (RFID) applications. The antenna consists of a compact printed dipole, a metasurface of 4 × 4 periodic metallic plates, and a metallic reflector. The dipole antenna is fed by a modified T-matching network for a conjugate impedance matching with the UCODE G2XM chip. The metasurface is designed to work as an artificial magnetic conductor surface, which allows low-profile configuration and unidirectional radiation. More interestingly, the finite-sized metasurface generates extra resonance for the antenna system, which is combined with the dipole resonance for the dual-band operation. For an easy realization and low cost, the dipole and metasurface are built on the top and bottom sides of a thin FR-4 substrate, respectively. The final design with overall size of 190 mm × 190 mm × 15.8 mm (0.532λ × 0.532λ × 0.044λ at 840 MHz) yields a simulated |S₁₁| < -10 dB bandwidth of 840-855 MHz and 916-932 MHz and a unidirectional radiation with a directivity of 7.0 dB and 5.8 dB at 925 MHz and 845 MHz, respectively. The antenna has been fabricated and tested. The measured readable range agrees rather closely with the predicted values. The measurements result in the maximum readable range of 6-m and 4.4-m at standard frequency bands of FCC (902-928 MHz) for North America and IN (840-845 MHz) for India, respectively.

This paper introduces a novel MIMO UWB antenna with dual notches. The proposed antenna is based on Quasi Self Complementary (QSC) method to give wide impedance bandwidth from 2.4 GHz to more than 12 GHz. The proposed antenna consists of a semi-elliptical patch that is fed by a tapered microstrip line. The antenna is designed on an FR-4 substrate with compact size 20 mm × 15 mm × 1.5 mm. The dual notched bands are achieved by using a square ring printed on the bottom of the substrate to reject WiMAX at 3.6 GHz. Also, a C-shaped slot is etched in the radiating patch to reject interference with the WLAN band at 5.8 GHz. In the proposed MIMO antenna, the isolation reduction is achieved utilizing diversity technique to minimize the mutual coupling between the antennas. The isolation between MIMO elements is more than 20 dB. The envelope correlation coefficient (ECC), diversity gain (DG), total active reflection coefficient (TARC), furthermore, channel capacity loss (CCL) are measured and calculated. The proposed antenna is designed, simulated, and measured. A good agreement is shown between the experimental and simulated results.

Statistical characteristics of scattered electromagnetic waves in the turbulent magnetized plasma caused by electron density fluctuations are calculated using complex geometrical optics approximation taking into account both diffraction effects and polarization coefficients. Scintillation level normalized on the variance of the phase fluctuations is analyzed analytically and numerically for small-scale plasma irregularities using the experimental data. New properties of the electromagnetic wave scintillations have been revealed. It is shown that splashes arise in the ionosphere leading to the turbulence and generation of new oscillations (waves and/or Pc pulsations) propagating in space and the terrestrial atmosphere. Turbulence extending in the lower atmospheric layers can influence on the meteorological parameters leading to climate change.

This paper introduces new compact microstrip line fed dual-band printed MIMO antennas resonating at 28 GHz and 38 GHz which are appropriate for 5G mobile communications. The first design in this work is a two-element conventional rectangular microstrip patch antenna with inset feed intended for 28 GHz and 38 GHz bands. The second design is symmetric dual-band two-element MIMO slotted-rectangular patches via microstrip inset fed lines. The dual-band response is attained from inverted I-shaped slots inserted in main patches. The third design is symmetric dual-band four-element MIMO antenna with inverted I-shaped slotted rectangular patches. A slot formed DGS is inserted in the partial rectangular ground plane. The substrate size is 55 x 110 mm², while the introduced antennas have very modest planar configurations and inhabit an insignificant area which make them fit easier within handset devices for the forthcoming 5G mobile communications. Better return losses and larger bandwidths are realized. The MIMO antennas have low mutual coupling without using any added constructions. The antenna systems offer appropriate values of directivity, gain, and radiation efficiency with anticipated reflection and correlation coefficient characteristics which are seemly for 5G mobile applications. The antenna systems are fabricated by a photolithography process that uses optic-radiation to copy the mask on a silicon slab by the aid of photoresist layers and measured using Vector Network Analyzer ZVA 67 (measures up to 67 GHz frequency) with a port impedance of 50 Ω.

In this article, a parasitic element structure is proposed to reduce the mutual coupling in a miniaturized microstrip dual-band Multiple-Input Multiple-Output (MIMO) antenna, which resonates at (7.8 GHz) for X-band and at (14.2 GHz) for Ku band applications. The design of the primary antenna consists of two identical radiators placed on a 24×20 mm² Fr-4 substrate, which are excited by orthogonal microstrip feed lines. In addition, a single complementary split ring resonator (S-CSRR) is used to improve the performance of proposed antenna. Simulation and measurement were used to study the antenna performance, including reflection coefficients, coupling between the two input ports, radiation efficiency and the radiation pattern. The measured results show that the proposed antenna achieves two operating bands with impedance bandwidths (|S₁₁| ≤ -10 dB) of 560 MHz (7.6 to 8.16 GHz) and 600 MHz (13.8 to 14.4 GHz) and mutual coupling (|S₁₂| < -26 dB), which are suitable for X/Ku band applications.

Compressed sensing (CS) is utilized in antenna measurements. The antenna data are compressed using the CS method, and the performances of different sparse and recovery algorithms of CS are used to solve antenna measurements. Experiments are conducted on various types of antennas. The results show that efficiency can be greatly improved by reducing the number of measurement points. The best reconstruction performance is exhibited by the Discrete Wavelet Transform (DWT) algorithm combined with the Compressive Sampling Matching Pursuit (COSAMP) algorithm.