A 5G metasurface (MS) transmitarray (TA) feed by compact-antenna array with the performance of high gain and side-lobe level (SLL) reduction is presented. The proposed MS has two identical metallic layers etched on both sides of the dielectric substrate and four fixed vias connecting two metallic layers that works at 28 GHz to increase the transmission phase shift range. The proposed planar TA consisting of unit cells with different dimensional information can simulate the function as an optical lens according to the Fermat’s principle, so the quasi-spherical wave emitted by the compact Potter horn antenna at the virtual focal point will transform to the quasi-plane wave by the phase-adjustments. Then, the particle swarm optimization (PSO) is introduced to optimize the phase distribution on the TA to decrease the SLL further. It is found that the optimized TA could achieve 27 dB gain at 28 GHz, 11.8% 3 dB gain bandwidth, −30 dB SLL, and aperture efficiency of 23% at the operating bandwidth of 27.5–29.5 GHz, which performs better than the nonoptimized one. The advanced particularities of this optimized TA including low cost, low profile, and easy to configure make it great potential in paving the way to 5G communication and radar system.

Unmanned aerial vehicles (UAVs) and infrared imaging technology have numerous applications in civilian fields. To address the issues of low accuracy resulting from complex ground backgrounds, small target size, and limited target features in UAV remote sensing infrared image target detection, we utilize the YOLOv9s model and the latest Retentive Networks Meet Vision Transformers technology, and propose the RMT-YOLOv9s model for infrared small target detection. Firstly, a CNN-RMT-based backbone is proposed by incorporating the RMT model into the backbone network of YOLOv9s, which extracts both local and global features for small target detection. Then, an improved neck multi-scale feature-fusion network RMTELAN-PANet is designed using the novel convolutional RMTELAN module proposed in this letter, which can better capture and utilize semantic information from feature maps. Finally, EMA attention module and upsampling Dysample module are integrated into RMTELAN-PANet to further improve the feature information of small targets. Experiments on the HIT-UAV dataset show that RMT-YOLOv9s outperforms other popular methods in infrared small target detection.

Laser fuze has the advantages of high distance accuracy and strong anti-electromagnetic interference capability, but it is easily disturbed by aerosols, such as smoke, which hinders its detection performance and application. This article proposes the dual wavelength frequency-modulated continuous wave (FMCW) laser detection technology as a solution. Compared with the single-wavelength FMCW laser fuze, the detection performance and the target recognition ability are enhanced under severe interference. First, the principles of dual wavelength FMCW laser detection are analyzed, followed by a block diagram of the fuze system. Second, the single scattering attenuation characteristics of spherical aerosol particles in reaction to different wavelengths of laser beams are discussed, and the scale distribution and complex refractive index characteristics and laws of four typical aerosol particles, including soot, ocean, dust, and water soluble, are analyzed. Finally, the echo characteristics of 0.3- and 10.6- $\mu \text{m}$ wavelength laser beams with or without a target are simulated and analyzed under the condition of typical aerosol heavy interference, and the spectral characteristics of the beat signal of the dual wavelength laser echo are obtained. According to this characteristic, a system for target recognition and distance determination using a dual-wavelength FMCW laser beam against aerosol interference is designed. The simulation results indicate that, in the presence of severe interference, the proposed system can effectively distinguish aerosol interference from the target and realize the accurate distance of the target.

In a smoke environment, suspended particles can scatter and absorb laser photons, making target echo signals extremely weak and difficult to extract and identify, which causes obvious difficulty in fixed-distance of laser fuze. In this paper, the multiple scattering model of frequency-modulated-continuous-wave (FMCW) laser fuze in a smoke environment was established. This model simulates multi-path propagation and multiple scattering of photons. At the same time, we use the correntropy spectral density (CSD) algorithm for accurate fixed-distance of FMCW laser fuze. The absolute error of distance does not exceed 0.15 m in smoke interference environment.