In order to improve the effectiveness of the antenna performance of wearable devices, a dual-band flexible monopole antenna with a 3 × 3 artificial magnetic conductor structure of the ISM band is proposed by using meander technology. An annular-shaped artificial magnetic conductor (AMC) is placed directly below the antenna, which can be better suitable for wireless body area network (WBAN) applications. A polyimide substance is used as the antenna substrate, which makes the antenna bendable and thin. Benefiting from the in-phase reflective properties of the double ring AMC structure, the antenna has good radiation characteristics. Compared with the single antenna, numerical simulation and measurement results show that the gain of the AMC-loaded antenna is increased by 4.54 dBi and 3.86 dBi at 2.45 GHz and 5.8 GHz, respectively. In addition, the specific absorption rate (SAR) of 1 g is only 0.35 W/kg at 2.45 GHz and 0.39 W/Kg at 5.8 GHz when the antenna is placed on human tissue, which is far below the Federal Communications Commission (FCC) standard. The antenna is easy to be conform to the human body and has strong robustness to structural deformation and human body load.

To accurately obtain the radiation and propagation characteristics of the highly oscillating electromagnetic (EM) waves, the p-refinement method which expands the physical quantities by high-order basis functions has been proposed. Nevertheless, since the time-domain EM simulation is a dynamic process, a static refinement is not applicable. In this communication, an efficient dynamic p-adaptation method based on hierarchical vector basis functions having the property of nesting to facilitate the construction of basis functions has been developed for the discontinuous Galerkin time-domain (DGTD) method. In this approach, based on the relationship between the amplitude of the expansion coefficients of hierarchical vector basis functions and the corresponding expansion coefficients of the physical quantities captured by each element in the previous time step, an error estimator is proposed to determine the order of each element in the next time step. To reduce the computational overhead, the basis orders of each element can be dynamically adjusted when the pulse passes through or is dissipated. The numerical results demonstrate the accuracy and efficiency of the proposed approach.

Three-dimensional object detection is the core of an autonomous driving perception system, which detects and analyzes targets around the vehicle to obtain their sizes, shapes, and categories to provide reliable operational decisions for achieving autonomous driving. To improve the detection and localization accuracy of multi-object targets such as surrounding vehicles and pedestrians in autonomous driving scenarios, based on PointPillars fast object detection network, a three-dimensional object detection algorithm based on the channel attention mechanism, ECA Modules-PointPillars, is proposed. Firstly, the improved algorithm uses point cloud columnarization features to convert a three-dimensional point cloud into a two-dimensional pseudo-image. Then, combining the 2D backbone network for feature extraction with the Efficient Channel Attention (ECA) modules to achieve the enhancement of the positional feature information in the pseudo-image and the weakening of the irrelevant feature information such as background noise. Finally, the single-shot multibox detector (SSD) algorithm was used to complete the 3D object detection task. The experimental results show that the improved algorithm improves the mAP by 3.84% and 4.04% in BEV mode and 3D mode, respectively, compared to PointPillars, which improves the mAP by 4.64% and 5.89% in BEV mode and 3D mode, respectively, compared to F-PointNet, improves the mAP by 11.78% and 14.19% in BEV mode and 3D mode, respectively, compared to VoxelNet, and improves the mAP by 9.47% and 6.55% in BEV mode and 3D mode, respectively, compared to SECOND, demonstrating the effectiveness and reliability of the improved algorithms in autonomous driving scenarios.

Based on the discontinuous Galerkin time-domain (DGTD) method, a new conformal perfectly matched layer (PML) is introduced to truncate the 3-D open domain. Compared with the traditional (rectangular or cubic) PML, the conformal PML is a smooth convex shell, which significantly reduces the buffer space in the computational domain. In this article, we construct the conformal PML in an orthogonal curvilinear coordinate system. Conductivities are defined to absorb the outgoing waves, depending on the distance from the sampling point to the non-PML region and the principal curvature radii of the sampling point, which are calculated utilizing the Weingarten transformation. The analytical expression of 3-D conformal PML is derived with the complex coordinate stretching technique. Furthermore, to reduce the total degrees of freedom (DoFs) while maintaining accuracy, the hierarchical vector basis functions are chosen to discretize the conformal PML and physical region. Numerical results validate its good absorption performance.

In this paper, we report a sequential-phase fed broadband circularly polarized array antenna loaded with an artificial magnetic conductor-reflecting surface. Our proposed antenna is a two-part group. The upper structure is a sequential-phase fed circular wide-slot antenna. The lower part is an artificial magnetic conductor structured reflective surface. The overall antenna size is 106 × 106 × 14.9 mm³, both adopting 1.6 mm thick FR4 material. The thickness of the air layer sandwiched between the antenna and the artificial magnetic conductor reflective surface is 14 mm. The antenna consists of four circular wide-slot antenna units with a sequential rotation technique. To broaden the axial ratio bandwidth, three L-shaped branches and four metal plates are attached to the circular wide-slot antenna unit and around the artificial magnetic conductor-reflecting surface, respectively. To verify the accuracy of the simulation, we fabricated the sample and then tested it in an anechoic chamber. The measured results demonstrate that the proposed broadband circularly polarized array antenna realizes an impedance bandwidth of 77.67% (2.74–6.22 GHz) and an axial ratio bandwidth of 65.16% (3.00–5.90 GHz) with a peak gain of 11.1 dBi. The design can be used in space-constrained environments, such as indoor and dense building areas.

In order to improve the performance of 5 G Millimeter wave, a new gap-coupled fed ultra-wideband circularly polarized antenna is proposed. Firstly, by fabricating the top structure of the slot antenna ，a C-shaped patch structure can adjust the surface transverse current as well as the longitudinal current to generate circularly polarized waves; then the feed structure at the bottom layer of the antenna is designed and resonance is generated with the top layer of the antenna to expand bandwidth. From the simulation and the measurement results can know that the −10 dB impedance bandwidth of the antenna is 19.21 GHz−45.50 GHz (81.25%); the 3 dB circularly polarized axial ratio (AR) bandwidth is 20.59 GHz−38.33 GHz (60.2%), with ultra-broadband circular polarization performance. The designed antenna has a simple structure, small size, low profile and wide working bandwidth, which can fully include N257, N258 and N261 bands, and has a good application prospect in 5 G communication.