Directional modulation (DM) technique has the ability to enhance the physical layer security (PLS) of wireless communications. Conventional DM schemes are usually based on a single antenna array with the basic assumption that eavesdroppers (Eves) and legitimate users (LUs) are in different directions. However, it is possible that Eves are in the same direction as LUs in practical applications. As a result, signals received by Eves will be approximately the same or even in better quality than those received by LUs. To address the neighbor security issue, we introduce a multiple antenna arrays model at the transmitter side with the help of the artificial noise (AN)-aided DM technique to achieve secure and precise DM transmission in this paper. Meanwhile, to recover the mixed useful signals, two novel DM schemes based on single- and multi-carrier multiple antenna arrays model are proposed, respectively. In addition, the symbol error rate (SER), secrecy rate, and robustness performance of the proposed DM schemes were analyzed and simulated. Simulations validate the effectiveness of the proposed DM schemes and demonstrate that multiple antenna arrays model based DM methods outperform single antenna array model aided DM methods in security.

A tiny dual‐band frequency selective surface structure is proposed in this paper. With dual‐band rejection characteristics at the corresponding frequency points of the S‐band and C‐band, suitable for antenna stealth. To achieve miniaturization, the unit‐cell architecture resembles the shape of a “S.” First of all, the author describes the parameters of the surface element, and then, the transmission characteristics of the surface element are analyzed by the equivalent circuit method. By maintaining a constant response to TE and TM polarization patterns and oblique incident angles, the suggested device ensures angular independence. The measured findings from the constructed FSS are used to validate the computed results. Finally, a new unit structure is provided for the application of FSS in antenna stealth.

UAV is difficult to detect by visual methods at a long distance, so a UAV detection and tracking algorithm is proposed based on image super-resolution. Firstly, a saliency transformation algorithm is built to focus on the suspected area. Then, a generative adversarial network is established on the basis of ROI to realize the super-resolution of weak targets and restore the high-resolution details of target features. Finally, the cooperative attention module is built to recognize and track UAV. Our experiments show that the proposed algorithm has strong robustness.

Reconfigurable intelligent surfaces (RISs) have emerged as a promising economical solution to implement cell-free networks. In this paper, the joint active and passive beamforming optimization of access points (APs) and RISs for the RISs-empowered cell-free network in the presence of channel state information (CSI) estimation errors is investigated. By taking the CSI estimation errors into account, we start with deriving the expression of a tight lower bound on the exact sum-rate, which is taken as the optimization criteria. Then, a robust joint beamforming optimization algorithm is proposed to obtain the highest sum-rate by using the lower bound, so as to obtain the best result out of the worst-case. In addition, a counter-intuitive but interesting result can be concluded via rigorous mathematical derivations that CSI estimation errors always impact the optimization of active transmitting beamforming matrices of APs, but surprisingly have no impact on the optimization of passive reflecting beamforming matrices of RISs when the covariance matrices of CSI estimation errors seen from two sides of each channel are proportional to an identity matrix. Simulation results demonstrate that RISs can considerably improve the sum-rate of the conventional cell-free network, and confirm the resilience of the proposed algorithm against CSI uncertainty.

Directional modulation (DM), as an emerging promising physical layer security (PLS) technique at the transmitter side with the help of an antenna array, has developed rapidly over decades. In this study, a DM technique using a polarization sensitive array (PSA) to produce the modulation with different polarization states (PSs) at different directions is investigated. A PSA, as a vector sensor, can be employed for more effective DM for an additional degree of freedom (DOF) provided in the polarization domain. The polarization information can be exploited to transmit different data streams simultaneously at the same directions, same frequency, but with different PSs in the desired directions to increase the channel capacity, and with random PSs off the desired directions to enhance PLS. The proposed method has the capability of concurrently projecting independent signals into different specified spatial directions while simultaneously distorting signal constellation in all other directions. The symbol error rate (SER), secrecy rate, and the robustness of the proposed DM scheme are analyzed. Design examples for single- and multi-beam DM systems are also presented. Simulations corroborate that (1) the proposed method is more effective for PLS; (2) the proposed DM scheme is more power-efficient than the traditional artificial noise aided DM schemes; and (3) the channel capacity is significantly improved compared with conventional scalar antenna arrays.

To address the challenges of imaging through scattering media, we propose GI_UNet, a differential ghost imaging (DGI) framework that integrates Monte Carlo photon-transport modeling with an enhanced UNet. By utilizing high-fidelity point spread functions (PSFs), the framework predicts the measurement matrix of trainable speckles after their propagation through scattering media, replacing the ideal illumination patterns used in traditional DGI. Subsequently, the enhanced UNet suppresses scattering noise and restores edge details through its optimized architectural components. Simulations and experiments demonstrate that GI_UNet outperforms existing mainstream methods. Given its imaging robustness under scattering conditions and at low sampling rates, GI_UNet provides an effective solution for various scattering-limited imaging scenarios.