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The Fermi bubbles and the eROSITA bubbles around the Milky Way Galaxy are speculated to be the aftermaths of past jet eruptions from a supermassive black hole in the galactic center. In this work, a 2.5D axisymmetric relativistic magnetohydrodynamic (RMHD) model is applied to simulate a jet eruption from our galactic center and to reconstruct the observed Fermi bubbles and eROSITA bubbles. High-energy non-thermal electrons are excited around forward shock and discontinuity transition regions in the simulated plasma distributions. The γ -ray and X-ray emissions from these electrons manifest patterns on the skymap that match the observed Fermi bubbles and eROSITA bubbles, respectively, in shape, size and radiation intensity. The influence of the background magnetic field, initial mass distribution in the Galaxy, and the jet parameters on the plasma distributions and hence these bubbles is analyzed. Subtle effects on the evolution of plasma distributions attributed to the adoption of a galactic disk model versus a spiral-arm model are also studied. [ABSTRACT FROM AUTHOR]

A complete framework of predicting the attributes of sea clutter under different operational conditions, specified by wind speed, wind direction, grazing angle, and polarization, is proposed for the first time. This framework is composed of empirical spectra to characterize sea-surface profiles under different wind speeds, the Monte Carlo method to generate realizations of sea-surface profiles, the physical-optics method to compute the normalized radar cross-sections (NRCSs) from individual sea-surface realizations, and regression of NRCS data (sea clutter) with an empirical probability density function (PDF) characterized by a few statistical parameters. JONSWAP and Hwang ocean-wave spectra are adopted to generate realizations of sea-surface profiles at low and high wind speeds, respectively. The probability density functions of NRCSs are regressed with K and Weibull distributions, each characterized by two parameters. The probability density functions in the outlier regions of weak and strong signals are regressed with a power-law distribution, each characterized by an index. The statistical parameters and power-law indices of the K and Weibull distributions are derived for the first time under different operational conditions. The study reveals succinct information of sea clutter that can be used to improve the radar performance in a wide variety of complicated ocean environments. The proposed framework can be used as a reference or guidelines for designing future measurement tasks to enhance the existing empirical models on ocean-wave spectra, normalized radar cross-sections, and so on. [ABSTRACT FROM AUTHOR]

A deep learning linear sampling method (DLSM), composed of linear sampling method (LSM) and a convolutional neural network (CNN) of U-Net, is proposed to restore shape of multilayered scatterers with cylindrical or rectangular cross section. Simulations over random samples with different geometrical parameters are used to verify the efficacy of the proposed method. [ABSTRACT FROM AUTHOR]

A dielectric resonator (DR) antenna with a well is proposed, of which the beamwidth is increased to more than 120[degrees] by bending the ground plane. This DR antenna has its 10-dB return-loss band in 3.4-3.8 GHz, thus can be used as a sectorial antenna in WiMAX (3.4-3.7 GHz) base station. Index Terms--Dielectric resonator (DR).

A phase-locked loop (PLL)-based frequency synthesizer at 5 GHz is designed and fabricated in 0.18-[micro]m CMOS technology. The power consumption of the synthesizer is significantly reduced by using an injection-locked frequency divider (ILFD) as the first frequency divider in the PLL feedback loop. The synthesizer chip consumes 18 mW of power, of which only 3.93 mW is consumed by the voltage-controlled oscillator (VCO) and the ILFD at 1.8-V supply voltage. The VCO has the phase noise of--104 dBc/Hz at 1-MHz offset and an output tuning range of 740 MHz. The chip size is 1.1 mm x 0.95 mm. Index Terms--Frequency divider, injection-locked frequency divider (ILFD), integer-N, low power, oscillator, phase-locked loop (PLL), receiver, synthesizer, voltage-controlled oscillator (VCO), wireless local area network (WLAN).

A broadband dielectric resonator (DR) antenna is proposed, which consists of a rectangular DR coated with metal on three sides and placed on a ground plane. The structure is analyzed by modelling the dielectric-air interface as perfect magnetic conductor (PMC). A coplanar waveguide (CPW) with terminating slots is used to feed the antenna. Measurement results exhihit a wide bandwidth of about 47% over which the [E.sub.[theta]] pattern on the horizontal plane is nearly omnidirectional. The 10-dB bandwidth of this broadband DR monopole covers 4.2-6.8 GHz. Hence, it can he used for WLAN 802.11a applications. Index Terms--Dielectric resonator (DR) antenna, monopole antenna.

A mode-matching technique combined with Galerkin's method is proposed in this paper to analyze the characteristics of striplines embedded in an inhomogeneous cylindrical medium. The potential in each layer is expressed in terms of eigenmodes obtained numerically. Coupling between two sets of eigenmodes in contiguous layers is described by defining potential ratio coefficient matrices. An integral equation is derived based on these eigenmodes with charge on the stripline as unknown. The method of moments is then applied to solve this integral equation. Various parameters are analyzed for their effects on transmission characteristics. Index Terms--Cylindrical striplines, Galerkin's method, inhomogeneous, integral equation, layered medium, mode matching, transmission characteristics.

A generalized potential-matching method incorporating reflection matrices is developed to calculate the capacitance of microshield lines with trapezoidal, circular, and V-shaped shields. Both completely shielded and half-shielded lines are analyzed. The effects of membrane thickness, strip width, and gapwidth on the characteristic impedance are studied. Index Terms - Capacitance, layered medium, microshield lines, potential-matching, reflection matrix.

Wave penetration through slits on single and stacked metal plates of finite thickness is studied by using the Galerkin method. The limiting case of slits on infinitesimally thin plates are also formulated to compare the shielding effectiveness of metal plates with slits against incident plane waves. It is observed that the wave penetrating through slits on stacked plates with a proper separation is much less than that through a single slit on a plate with twice the thickness. Index Terms - Galerkin's method, shielding, slits.

Two types of linear coaxial antennas, coaxial-colinear antennas, and slotted coaxial antennas are studied to check the possibility of using them as the base-station antenna in personal communication systems. The slot voltages and input impedance of linear coaxial antennas are obtained by using a transmission-line analysis where the radiation effect is accounted by a shunt and a serial admittance, respectively. The current distribution is obtained by solving an integral equation using the method of moments. The radiation pattern and directivity are then obtained from the current distribution and the reflection coefficient inside the coaxial cable. Factors analyzed include frequency, coaxial filling permittivity, and segment number. Index Terms - Coaxial-colinear antenna, field pattern, gain, input impedance, slotted coaxial antenna, transmission line analysis.

Several types of periodical surfaces are studied on their backscattering to a normally incident TE plane wave. The surfaces are perfect conductor and are covered with dielectric materials to make a flat surface due to aerodynamic consideration. The effects of frequency, surface profile shape, period-to-depth ratio, and cover permittivity are analyzed. It is observed that a sawtooth profile can be used to reduce the backscattering at high frequencies and elliptical profiles can be used to reduce the backscattering at certain low frequencies when a cover material is filled in the grooves. Index Terms - Electromagnetic scattering, periodic structures.

The propagation properties of microstrip lines on a substrate with inhomogeneous permittivity and conductivity profiles are analyzed. The eigenmodes in each inhomogeneous layer are obtained by solving an eigen equation. These eigenmodes are then used to formulate the Green's function of the stratified medium. An integral equation is next derived in terms of the surface current on the strip. Galerkin's method is then applied to obtain a determinantal equation to be solved for the propagation constant. The effect of several permittivity and conductivity profiles are analyzed. Index Terms - Dispersion relation, inhomogeneous substrate, microstrip line, stratified medium.

Both the Galerkin's and mode-matching methods are used to analyze the reflection and radiation properties of a coaxial cable with a circumferential slot on the outer conductor. The effects of higher order modes are also included. The accumulated effect of multiple slots on the reflected signal is also studied by using a Monte Carlo simulation. Index Terms - Coaxial cable, Galerkin's method, mode-matching, Monte Carlo simulation, slot radiation.

A generic numerical scheme is developed to calculate the resonant frequency of axisymmetric modes in an inhomogeneous cylindrical dielectric resonator. The resonator consists of sections of cylindrically stratified dielectrics within a cylindrical waveguide. In each section, the [TM.sub.0m] and [TE.sub.0m] waveguide modes are solved by expanding the [H.sub.[Phi]] and [E.sub.[Phi]] components in terms of the eigenmodes in an empty waveguide. The fields in each section are then expanded in terms of these T[M.sub.0m] and T[E.sub.0m] modes. The transverse resonance technique is then applied to obtain the resonant frequencies. Comparison with literatures validates the effectiveness of this approach. Results with continuous dielectric profiles are also obtained.

In this paper, we study the normalized wavelength and attenuation constant of coplanar waveguides with a finite metal thickness. The substrate is a lossy inhomogeneous insulator-semiconductor, and the conductor is assumed perfect. Electroquasi-static approximation is used to derive a Laplace's equation with a complex permittivity in each inhomogeneous layer, from which the eigenmodes are obtained. Proper boundary conditions between contiguous layers are applied to calculate the charge distribution on the center conductor. The effects of the insulator depth and semiconductor conductivity on the normalized wavelength and attenuation constant are analyzed.

In this paper, we analyze the effect of laminated ground plane on the propagation and coupling characteristics of microstrip lines. Each lamina is modeled as an anisotropic layer, and transition matrix is used to relate the tangential field components in different laminae. An integral equation is formulated in the spectral domain, and the Galerkin's method is applied to solve the integral equation for the phase and the attenuation constants of several microstrip line structures. The effects of substrate dielectric are also studied. The attenuation constant variation thus obtained will be useful in circuit board design and in studying signal transmission in lamina environment.