A wideband frequency diversity printed-Yagi antenna array is presented. The operating band of the single port L-/S-bands antenna element can be selected by changing the states of p-i-n diode switches. The Land S-bands work independently. A 4 × 4 S-band array can be constituted to a 2 × 2 L-band array by modifying the element apertures. This array operates at 1-2 GHz/2-4 GHz in the L-/S-bands with a fractional bandwidth of 66.7%/66.7%, which is translated into an overall tuning ratio of 4:1. The spacing of adjacent antenna elements at each reconfigurable mode is less than 0.72λ ₀ (λ ₀ represents the free-space wavelength of the highest frequency in the operating band), which achieves no grating lobes in the radiation held. The proposed antenna array is simulated, fabricated, and tested with reasonable agreement between measurements and simulations. In this way, a rudiment of wider tuning ratio array is designed for wideband reconnaissance applications.

In this article, a dual-band X/Ku co-polarized shared-aperture waveguide slot antenna is proposed. The frequency ratio is 1.4:1. Both frequency bands utilize broadside longitudinal slots for radiating. To achieve a shared-aperture design for the dual-band waveguide arrays within a confined space, structural optimization is primarily conducted on the linear array for the lower frequency band. Based on the design of the X-band radiation waveguide, longitudinal slots distribution at the center of the broadside achieves consistent feeding phase, which further facilitate the design of the X-band linear array within a limited width of only 0.13 $\lambda _{0}$ . The proposed shared-aperture antenna exhibits good impedance matching and radiation characteristics. Furthermore, the proposed antenna features a modular design, which is advantageous for flexibly changing the scale of the antenna array as needed. Due to the characteristics mentioned above, the proposed antenna array is a promising candidate for airborne and spaceborne SAR systems, especially for those that require simultaneous operation in different frequency bands.

Satellite fog computing (SFC) achieves computation, caching, and other functionalities through collaboration among fog nodes. Satellites can provide real-time and reliable satellite-to-ground fusion services by pre-caching content that users may request in advance. However, due to the high-speed mobility of satellites, the complexity of user-access conditions poses a new challenge in selecting optimal caching locations and improving caching efficiency. Motivated by this, in this paper, we propose a real-time caching scheme based on a Double Deep Q-Network (Double DQN). The overarching objective is to enhance the cache hit rate. The simulation results demonstrate that the algorithm proposed in this paper improves the data hit rate by approximately 13% compared to methods without reinforcement learning assistance.

A frequency reconfigurable antenna array is presented. The array consists of eight arms with two different feed networks. By controlling PIN diode switches, high frequency array with four dipole elements and low frequency array with two dipole elements can be obtained, respectively. Resonant frequencies within the ranges of 1.0–2.5 GHz (Case I) and 2.5–6.0 GHz (Case II) can be achieved, which translates into an overall tuning ratio of 6:1 (1.0–6.0 GHz) for the antenna array. The proposed antenna array is simulated, fabricated, and tested with good agreement between measurements and simulations.