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.

An accelerated shooting and bouncing ray (SBR) method is presented in this letter to improve the efficiency of radar cross section (RCS) prediction for electrically large and complex objects. The SBR method is inefficient because it needs to trace a large number of ray tubes. Therefore, its efficiency can be improved by reducing the amount of ray tubes and increasing the speed of ray tracing. In this paper, we use rays instead of ray tubes to reduce the amount of rays that need to be traced, and construct a virtual ray tube (VRT) at the ray exit position for field integration. Moreover, ray tracing and integration operations are executed on the graphics processing unit (GPU) to further improve the efficiency of SBR method. Several examples are designed to prove the effectiveness of the proposed method.

In this letter, a closed-loop cross-dipole antenna array (CLCDAA) is proposed for wideband orbital angular momentum (OAM) communication. The proposed antenna array is designed based on a closed-loop cross-dipoles patch (CDP), several pillow-like parasitic patches (PLPPs) and a hybrid wideband feeding network. The design method of the feeding network is introduced using the analysis of multiport network, and the good performance of this feeding network is verified. A prototype CLCDAA is fabricated and measured to validate the design concept. The OAM beams can cover a wide frequency band from 2.08 GHz to 3.95 GHz (FBW: 62.02 %), and the simulation and measurement results are in good agreement. Benefiting from compact structure, simple design procedure, and steady performance, the proposed antenna array has a significant meaning in the application of wireless communications.

In this letter, an accelerated physical optics (PO) method is proposed to improve the calculation speed of electromagnetic (EM) scattering from electrically large targets. One of the most time-consuming parts of PO is the shadowing test of target model. The traditional method shadows the model by determining the occlusion relationship between each two triangular facets. The coupling between facets is strong, and it makes low running speed when using the traditional method. The proposed method accelerates the shadowing test by grouping facets to weaken the coupling between them. It eliminates a large number of redundant operations and significantly improves the efficiency of EM scattering calculation. Several examples are designed to prove the effectiveness of the proposed method.

Rock breakage is inevitable for creating openings in underground engineering operations. Ultrasonic vibration has been attracting extensive attention for such a practice considering its outstanding performance in rock breakage. In order to understand the fundamental failure mechanism of rocks subjected to ultrasonic vibrations, based on P-wave monitoring and the direct current electric method, we captured the evolution of the failure process of the red sandstone. In addition, we fundamentally analyse the failure mechanisms of the red sandstone using numerical simulation and microscopy scans. It was found that extensive fractures were initiated due to the ultrasonic vibration and the fractures propagated downwards forming a conical shape. The apparent resistivity became as high as 320000 Ω being 16 times the initial resistivity. The fracture propagated downwards as deep as 41 mm. The maximum damage parameter on the testing sample could be as high as 0.68, and it completely failed after 140 s of ultrasonic vibration duration. As a result of numerical simulation, it was found that the microfractures and pores in the testing sample were activated due to the stress wave resulting from the ultrasonic vibration leading to the fracture propagation and eventually complete failure. Through comparing the performance of uniaxial compressive loading and ultrasonic vibration techniques in rock damage, it was concluded the latter has a much higher capacity and competence in rock breakage.

A method for suppressing off-board active mainlobe interference based on situational awareness is proposed to address the challenge of inaccurate real target tracking and detection in linear frequency modulation (LFM) radar systems under dynamic confrontation scenarios. Initially, a cognitive closed-loop integrated interference suppression framework is outlined, encompassing interference cognition, weight determination, and cognitive mainlobe interference suppression. Subsequently, a temporal sequence control mainlobe interference suppression method is proposed. This method dynamically adjusts the weights of sum and difference receiving channels of the LFM radar system to combat mainlobe interference by analyzing the temporal sequence of various signal types in radar echoes. Furthermore, an unsupervised hybrid cognition model for interference cognition and parameter estimation is proposed to support the temporal control mechanism. Signal temporal sequence and type information is achieved by combining complex domain features. Ultimately, the dynamic interference suppression effect of the cognitive closed-loop system is realized. The effectiveness of the proposed method is validated through simulation and over-the-air experiments, demonstrating an 18.7 dB improvement in the signal-to-interference-plus-noise ratio (SINR) compared to the traditional non-weighted strategy.