This paper presents a trust-region parallel Bayesian optimization (TRPBO) method for simulation-driven antenna design problems. In this method, a multi-points acquisition function and trust region-based design space were developed to accelerate the solution efficiency of antenna design optimizations. For each optimization cycle in TRPBO, the acquisition function is applied to choose multiple updating points in a dynamic sampling space managed by a gradient-free trust region, and then the responses at the updating points are calculated using parallel electromagnetic simulations. The proposed TRPBO was illustrated and tested on several benchmark problems, and then the TRPBO was applied to perform the design optimizations of a circularly polarized antenna, two wideband antennas and an array antenna. Compared with the state-of-the-art methods, the proposed TRPBO achieves better optimization results with significantly less calculation time. The measured results of three fabricated antenna prototypes further show great potential of the TRPBO for solving simulation-driven antenna design problems.

The problem of tiny and low-contrast surface defect detection is a nontrivial one. To solve the problems, this article proposes an edge and multi-scale reverse attention network (EMRA-Net), of which includes feature extraction and feature fusion. In the process feature extraction, the global dynamic convolution features, global dynamic multi-scale fusion (MSF) feature, and local pyramid edge feature are obtained through the pre-training backbone Resnet 34, the fresh MSF module, and the innovative pyramid edge module, respectively. In the process of feature fusion, these features are blended by a new self-learning scale module and a novel spatial channel domain reverse attention (SCRA) module step by step. The experimental results of five widely used datasets show that the EMRA-Net outperforms the existing methods. In addition, the mean intersection of union (mIoU) ^{1 2} on the printed circuit board (PCB) industry dataset reaches 95.31%. Moreover, the results of EMRA-Net indicated that the local edge feature can improve the performance of the defect detection network. The EMRA-Net has great potential in the application in the detection of tiny and low-contrast defects.

An orbital angular momentum (OAM) mode-reconfigurable antenna based on uniform circular array (UCA) is presented. To realize multiple switchable operating states while maintaining a relatively simple structure, a simplified feeding scheme is developed. By introducing a set of optimal reference phases for different OAM modes, the tunable phase states for the entire array are degenerated, which leads to a reduction of the total number of required phase states. Then the excitation phases are decomposed into two parts and generated by the reconfigurable radiators and reconfigurable feed network, respectively. In addition, p-i-n diodes are selected as switches to control the operating states of the radiators and feed network. Therefore, OAM mode switching capability can be obtained by altering the direct current (dc) bias configurations of the diodes. The antenna design is validated by both simulation and measurement. Results indicate that the proposed eight-element array antenna produces six operating states corresponding to OAM modes l=±1, ±2 and ±3. The measured overlapped band among the states with |S11|< -15 dB covers 2.33-2.73 GHz. Moreover, the proposed antenna also features the advantages of easy fabrication and low cost.

A reconfigurable antenna with a compact size and quad-polarization reconfigurability is presented. By employing a switchable feed scheme, the antenna can operate at single-fed and dual-fed modes. At single-fed mode, the feed structure allows output ports switching to produce the excitations for either slant +45° or −45° linear polarization (LP). At dual-fed mode, it serves as a switchable phase-shifting power splitter for generating left-hand circular polarization (LHCP) or right-hand circular polarization (RHCP). To realize a simple and space-saving configuration, the antenna makes efficient use of the proposed feed structure, which is highly shared among the four polarization states. Measured results show that the antenna exhibits operating bandwidths of 230 and 260 MHz at circular polarization CP and LP states, respectively. Moreover, stable broadside radiation patterns as well as moderate gains could also be obtained.

A circular polarization (CP)-agile and continuous beam-steerable array antenna is presented using a hybrid design approach. It is accomplished by combining digital reconfigurable antenna elements with analog continuously tunable phase shifters. To realize both polarization reconfiguration and initial phase generation for beam scanning simultaneously, the designed antenna element enables eight states that correspond to two CP modes with four quantized phases. The phase shifters further provide additional variable phases of −90° to 0° for antenna element excitation. Superposition of the initial and additional phases helps to satisfy full and continuous 360° phase coverage for a beam-steerable array. Meanwhile, phase decomposition also facilitates the design of phase shifters without complex or cascaded structures. By altering the bias states of the electronic components loaded in the array antenna, CP switching and beam scanning can be independently controlled. For verification, prototypes of the antenna element, phase shifter, and a four-element array are all fabricated and tested. Reasonable agreement is obtained between simulation and measurement. The resultant array could scan up to nearly ±40° off the boresight, along with stable radiation patterns and good CP performance.

This paper investigates the problem of an optimal sensor placement for better shape deformation sensing of a new antenna structure with embedded or attached Fiber Bragg grating (FBG) strain sensors. In this paper, the deformation shape of the antenna structure is reconstructed using a strain–displacement transformation, according to the measured discrete strain data from limited FBG strain sensors. Moreover, a two-stage sensor placement method is proposed using a derived relative reconstruction error equation. In this method, the initial sensor locations are determined using the principal component analysis based on orthogonal trigonometric (i.e., QR) decomposition, and then a new location is sequentially added into the initial sensor locations one by one by minimizing the relative reconstruction error considering information redundancy. The numerical simulations are conducted, and the comparisons show that the proposed method is advantageous in terms of the sensor distribution and computational cost. Experimental validation is performed using an antenna experimental platform equipped with an optimal FBG strain sensor configuration, and the reconstruction results show good agreements with those measured directly from displacement sensors. The proposed method has a large potential for the strain sensor placement of complex structures, and the proposed antenna structure with FBG strain sensors can be applied to the future wing-skin antenna or flexible space-based antenna.