Rydberg atom-based antennas exploit the quantum properties of highly excited Rydberg atoms, providing unique advantages over classical antennas, such as high sensitivity, broad frequency range, and low intrinsic noise. Despite the increasing interests in their applications in antenna and communication engineering, some key properties, involving the lack of polarization multiplexing and isotropic reception without mutual coupling, remain unexplored in the analysis of Rydberg atom-based multiple-input and multiple-output (MIMO) communications. Generally, the design considerations for any antenna, even for atomic ones, can be extracted to factors such as radiation pattern, efficiency, and polarization, allowing them to be seamlessly integrated into existing system models. In this letter, we extract the antenna properties from relevant quantum characteristics, enabling electromagnetic modeling and capacity analysis of Rydberg MIMO systems in both far-field and near-field scenarios. Focusing on spatial multiplexing performance under the same signal-to-noise (SNR) level, our results indicate that Rydberg atom-based antenna arrays offer certain advantages over classical dipole -type arrays in single-polarization MIMO communications.

In this paper, a novel ultra-wideband circularly polarized (CP) orthogonal magnetic dipole (OMD) antenna array with a dual-mode sequential rotation feeding (SRF) networks is proposed for the millimeter-wave (mm-wave) applications. Above all, a novel OMD concept model is proposed. Subsequently, based on the conceptual model, a planar CP OMD antenna element is designed and analyzed, and its axial ratio (AR) bandwidth is enhanced by using parasitic patches. To further achieve a wider AR bandwidth and a higher gain, a dual-mode SRF network is proposed and designed to form a 4 × 4 CP antenna array. Finally, the antenna array is fabricated and measured to verify the design. The measurement results of the proposed 4×4 CP array show a -10-dB impedance bandwidth of 88.3% (18.15-46.85 GHz) and a 3-dB AR bandwidth of 61.0% (20.5-38.5 GHz) with a peak gain of 16.8 dBic. The proposed antenna array boasts several advantages, such as wide impedance and AR bandwidths and ease of integration, making it suitable for a wide range of applications in 5G mm-wave communication systems.

The recently proposed complying-divergence implicit finite-difference time-domain (CDI-FDTD) method was demonstrated with relatively superior numerical performance, especially with the unconditional stability of implicit methods and the complying-divergence property. In addition, the complying-divergence property was also extended to and successful utilized in semi-implicit FDTD methods for significantly more efficient and accurate electromagnetic (EM) computations with models containing fine structures in one or two directions. This work offers an effective implementation of the complex frequency-shifted perfectly matched layer (CFS-PML) based on a one-step leapfrog CD-hybrid implicit-explicit FDTD (CD-HIE-FDTD) method with more robust simulations to address more complicated open-domain EM challenges. The stretching factors are initially introduced into Maxwell’s equations to derive a compact first-order differential matrix form. Subsequently, the matrix is subjected to space-time operator splitting to establish a complying-divergence framework with a two-step iterative solution. For more numerical efficiency, we utilize the leapfrog time-stepping strategy to eliminate intermediate variables and get a one-step iterative solution. Moreover, for the aforementioned computational framework, we offer an analysis for the terms of numerical stability and complying-divergence property. Meanwhile, the various examples given in this work also verify the correctness and efficacy of the proposed method.

This study introduces a novel, unified arbitrary-order matrix exponential-symplectic FDTD^(p,q) (ME-SFDTD^(p,q)) method tailored for simulating anisotropic time-varying plasma medium. The governing equations, comprising both current density and Maxwell’s equations, are reformulated into a compact first-order differential matrix form and then discretized in the temporal domain using a multistage p-order symplectic integrator. Meanwhile, the matrix exponential (ME) coefficients arising from the symplectic discretization are efficiently computed utilizing the ME method, while spatial derivatives are approximated by a q-order central-difference scheme. These processes yield a complete numerical iteration framework specific to the ME-SFDTD^(p,q) format, optimized for field components calculations in an anisotropic time-varying plasma medium. To effectively truncate the simulation space modeled by the ME-SFDTD^(p,q) method, a high-performance complex frequency-shifted perfectly matched layer (CFS-PML) technique is proposed, which shares the same primary iteration formulas as the ME-SFDTD^(p,q) method, exhibiting excellent absorption performance and high compatibility. In addition, a comprehensive numerical stability and dispersion analysis is conducted to confirm the feasibility of the proposed method. Finally, several numerical examples are presented to thoroughly validate the accuracy and efficiency of the approach.

This article introduces a computational approach that utilizes the stochastic finite-difference time-domain (S-FDTD) method to solve problems involving both electromagnetic and thermal fields with uncertainty parameters. This stochastic solver not only considers electrical parameters such as permittivity and permeability as random variables, but also takes into account thermal parameters such as specific heat capacity and thermal conductivity. In addition, two different simulation strategies were proposed for the specific implementation of electromagnetic-thermal coupling. As a result, the proposed algorithm achieves statistical estimation of uncertainty in the multiphysical co-simulation of electromagnetic fields and thermal fields. This article presents the procedure and intricacies of formula derivation for the proposed method. Furthermore, the precision and feasibility of the proposed method are verified through simulations of layered tissue models with reference to Monte Carlo results. The simulation of a complex human head model demonstrates that the proposed method is capable of handling complex objects and meeting practical application requirements. This method has wide applications in biomedical applications and electromagnetic protection and provides theoretical and technical support for statistical estimation in these areas.

A circularly polarized (CP) reconfigurable and linear polarized (LP) orbital angular momentum (OAM) mode multiplexing concentric uniform circular array (CUCA) is presented. The designed antenna array consists of two parts: an inner UCA composed of four LP antenna elements and an external UCA composed of eight sequentially rotated CP reconfigurable elements. The inner UCA and outer UCA are capable of generating multiplexed OAM beams at 3.28 GHz with l = +1 and mode l = ±2, respectively. To assess the performance of these vortex beams, a purity analysis of the multiplexed OAM modes was conducted. When all elements are fed with the same amplitude signal, the mode purity of the inner UCA at l = +1 with LP is 27.6%. As for the external UCA, at l = +2 with right-hand CP (RHCP), the mode purity in the electric field Ex- component is 32.5%, and in the Ey- component, it is 47.5%. Furthermore, l = -2 with left-hand CP (LHCP) has similar results. The obtained results are consistent, validating the potential application of the proposed modal multiplexing method in future communication.