A review of photonic integrated optical phased array (OPA) for space optical communication is presented. We review and summarize the typical works of the photonic integrated OPAs with onedimensional and two-dimensional optical antenna array in recent years. The basic components of the photonic integrated OPA are introduced separately, including optical coupler, optical power division network, phase shifter, and optical antenna. In addition, the configuration of the optical antenna array and the control circuit are introduced for OPA beam steering. The basic principle and experiment setup for testing the radiation properties of the OPA are presented. A proof-of-concept nonuniform silicon integrated OPA with 64 antennas is designed and a one-dimensional beam steering range of 280 is achieved with beam width of about 0.250. The challenges and development trends of large-scale integrated OPA chip applied in space optical communication are also discussed.

Metamaterials are an artificial electromagnetic material composed of periodic/non-periodic subwavelength micro-/nanostructures, i.e. meta-atoms. The meta-atom interacts with the incident electromagnetic wave and introduces electromagnetic resonance, which makes the metamaterial exhibit the desired electromagnetic characteristics. Therefore, the electromagnetic wave can be controlled by changing the geometry, configuration and distribution of the meta-atoms. Due to their flexible electromagnetic manipulation ability, metamaterials have attracted great interest in many fields, such as super-resolution imaging, high-sensitive detection, aerocraft stealth and laser-machining. A planar metamaterial with one or a few layers of meta-atoms is called a metasurface. The metasurface can not only manipulate the amplitude, phase and polarization of the electromagnetic waves, but also has the advantages of being ultra-thin, ultra-light and easy to process. In the terahertz (THz) region, more and more devices based on metasurfaces have been proposed for spectrum modulation and wavefront shaping, which has contributed to the rapid development of THz technology. This paper reviews the design principles and research progress of metamaterials/metasurfaces for spectrum modulation, wavefront shaping, polarization conversion and surface wave manipulation in the THz region. Active metamaterials can be used to manipulate electromagnetic waves dynamically, and this will become a research field with great application potential. In this review, the implementation schemes and research results of various active THz metamaterial devices are reviewed in detail. Furthermore, the potential applications of metamaterials/metasurfaces in security, high-capacity communication, biomedicine and other fields are analyzed. Finally, we discuss the future developments and challenges of THz metamaterials.

Relying on space-air-ground (SAG)-integrated artificial intelligence of everything (AIoE) networks, massive computation-intensive and latency-sensitive tasks can be efficiently either executed locally by ground AIoE users, or offloaded to SAG servers, such as remote base stations, aerial high altitude platform (HAP) and low earth orbit satellites. However, joint optimization of communication and computation resources becomes a great challenge considering dynamic network environment, large-scale coverage and battery energy backup constraint. Hence, in this paper, we propose a SAG-integrated heterogenous computation offloading architecture for the deep integration of communication and computation resources in order to maximize the sum-rate of all AIoE users. Moreover, we propose a multi-agent proximal policy optimization algorithm with the aid of Lyapunov-based profile to solve the task scheduling and HAP selection. And a convex optimization based communication and computation resource allocation scheme processes the CPU-cycle frequency and transmission power. The battery energy backup is tackled via the linear programming policy. Experimental results demonstrate that our proposed method outperforms existing state-of-the-art baselines in terms of convergence speed, average sum-rate and battery backup level of AIoE users.

A low cost, dual circularly polarized (CP) 2-bit antenna working at 10 GHz is reported in this work. The antenna element utilizes a square-ring patch as radiator. By selecting the feeding direction of the T-shaped coupling microstrip line and the position of perturbation corner, the 2-bit phase of 0°, 90°, 180°, 270°, and the CP reconfigurability can be realized. An 8-element linear array is used to verify the beam scanning performance. By controlling the ‘ON’ or ‘OFF’ of the p-i-n diodes, the prototype array can steer the main beam from 0° to 40°. Within these steering beams, simulated and measured results have a good agreement, which verifies the functions of the antenna.

This paper presents a novel tri-band antenna with dual polarizations and shared aperture. The proposed antenna operates at $L$ -, $S$ -, and $X$ -bands with an approximate frequency ratio of 1:1.9:5.5. Three types of radiation elements resonating at different frequencies, including the square microstrip patch, microstrip dipole, and printed monopole, are interlaced in the same aperture. Printed monopole with a fork-shaped stub is adopted as the $L$ -band element due to its wideband ability. Both the $S$ - and $X$ -band elements adopt a stacked structure to enhance the bandwidth. Besides, the $S$ -band element employs a stepped gradient structure that can obtain a wider bandwidth than the normal microstrip dipole. The measured results agree well with the simulations. The measured impedance bandwidths of $L$ -, $S$ -, and $X$ -bands are 21.7%, 11.6%, and 18.9%, respectively. The measured isolation at $L$ -, $S$ -, and $X$ -bands is higher than 25, 38, and 29 dB, respectively. The antenna also exhibits an excellent radiation performance with the high cross-polarization discrimination at the three bands. To the best of the authors’ knowledge, this is the first shared-aperture $L$ -/ $S$ -/ $X$ -band dual-polarized broadband antenna in a true sense, which is useful for potential synthetic aperture radar applications.