We report on developments in the evaluation of matrix elements of the electric and magnetic field operators involving the asymptotic (large transverse wave-number or small transverse distances) components of the mixed-potential Green’s function of a layered medium. Subtracting these asymptotic terms significantly accelerates numerical computation of the Sommerfeld-type integrals required in constructing Green’s function and then x elements [1]. The described method is applicable to planar conducting structures embedded in a multi-layered medium. Ability of a fast and accurate evaluation of matrix elements for such structures is critical in many applications, especially in solving forward problems in design and optimization of electromagnetic metasurfaces.
This paper reports a method for bandwidth enhancement of radar cross section (RCS) reduction by metasurfaces. Scattering cancellation is one of the common methods for reducing RCS of target scatterers. It occurs when the wave reflected by the target scatterer and the wave reflected by the cancelling scatterer are the same amplitude and opposite phase. Since the bandwidth of the scattering cancellation is usually narrow, we propose a bandwidth enhancement method by metasurfaces that can control the frequency dependence of the scattering phase. We designed and fabricated a metasurface composed of a patch array on a grounded dielectric substrate. We confirmed that the metasurface gives broader bandwidth of 10dB RCS reduction than the metallic canceling scatterer.
GNSS is an important source for train location, which provides continuous train location possibilities for train operation. As GNSS positioning principle is radio localization using TOA (Time of Arrival), the radio signals are susceptible to the environment its propagated, location accuracy is dependent on the environment. According to the propagation of the radio signals, they can be divided into three categories: LOS (Line-of-Sight), NLOS (Non-Line-of-Sight) and non-visible. To quantify the ground-related satellite signal propagation error applied to typical train localization environments, this paper addresses two sets of statistical properties-based local pseudorange model for both occluded-signal and non-occluded signal. This paper takes urban canyon as an example for analysis. Firstly, the occluded-signal and non-occluded-signal are divided based on the obstacle boundary shown in the skyplot. Secondly, the difference elimination between user and stations based on CORS network is used to extract the ground-related pseudorange error. The 10-hour static observation data show that the mean and dispersion of the local pseudorange error of the occluded-signal are significantly larger than those of the non-occluded-signal, and are negatively correlated with the elevation range. The distribution of the occluded-signal is multimodal, and the GMM model is used to describe it. The distribution of non-occluded-signal shows non-Gaussian, and the steepness of the distribution changes with the elevation, which the T Location-Scale distribution model is used for reasonable description.
Quantum computers, through quantum entanglement and parallelization, offer an intriguing prospect of exponential speedup relative to classical computers for performing numerical simulations. Our interest is in the application of quantum information science to plasma physics in order to develop algorithms which can implemented on quantum computers. Concurrently, we want to test these algorithms on present conventional (classical) computers as large scale, error-correcting quantum computers with long coherence times are not yet forthcoming. Even though the constituents of laboratory and space plasmas are electrons and ions, the physics of these plasmas is dominated by collective processes. Quantum effects that are prominent at sub-atomic scales are averaged out in the statistical description of a plasma. Consequently, we need to render classical plasma physics in the language of quantum mechanics in preparation for quantum computers.
The high scanning rate and scanning linearity of leaky-wave antennas (LWA) have attracted a lot of attentions, since it can reduce both the occupation of electromagnetic spectrum resources and requirements of accuracy for transmitters and receivers, respectively [1]. As shown in Figure 1, the radiation angle of an ideal linear scanning LWA is directly proportional to its frequency, which can be described as:
