Janus metasurface, as a class of nonreciprocal two-dimensional metamaterial, empowers independent wavefront manipulation of electromagnetic (EM) waves from distinct k-directions, establishes a new paradigm for multifunctional integrated devices. However, most reported Janus metasurfaces are mainly based on pure phase modulation without taking amplitude manipulation into consideration, which limits the degree of freedom in EM wave control and reduces the information capacity and imaging quality. Here, a novel full-space Janus metasurface with amplitude-phase joint coding is proposed for the first time, which integrates a nonreciprocal transmission and bidirectional reflection at two different frequencies. Moreover, both transmission and reflection can achieve independent amplitude-phase control. As a proof of concept, a full-space holography based on proposed Janus metasurface is designed and fabricated. Simulated and measured results are in good agreements with the theoretical predictions, verifying the good performance of the proposed Janus metasurface, which demonstrates potential applications in big data storage and high-quality imaging.
Accurate glucose-dependent dielectric models of blood are essential for designing and validating microwave-based glucose sensors. In this work, broadband dielectric spectroscopy is performed on blood from mice with streptozotocin-induced hyperglycemia, covering a fasting blood glucose range of 74–600 over 0.5–20 GHz using an open-ended coaxial probe. The extracted dielectric constant and conductivity generally decrease with increasing glucose concentration, with the absolute difference between the highest and lowest glucose levels being largest at 0.5–8 GHz for dielectric constant and 17.5–20 GHz for conductivity. Single- and double-term Debye and Cole–Cole relaxation models are compared using the Akaike Information Criterion (AIC) and root mean square error (RMSE). The double Debye model is selected, achieving a mean RMSE of 0.319 and 0.254 for the real and imaginary permittivity across the four tested concentrations, with $\Delta \text{AIC}=5.3$ relative to the double Cole–Cole model, favoring the simpler parameterization. The model coefficients are expressed as second-order polynomial functions of glucose concentration, enabling the dielectric properties to be reconstructed as a function of frequency and glucose level within the measured range. A blood-mimicking phantom formulated from phosphate-buffered saline, bovine serum albumin, glucose, and polystyrene microparticles shows a mean absolute difference of 0.83 for $\epsilon ^{\prime }$ and 0.44 S/m for $\sigma$, averaged across the full band and three glucose concentrations (133, 320, and 600 mg/dL). This study provides reference dielectric data, a glucose-dependent parametric model for full-wave electromagnetic simulation, and a reproducible phantom for microwave glucose sensor development.
In this study, the design and evaluation of an octagonal microwave cavity equipped with different feeding networks for uniform heating applications are presented. The cavity is intended for the food processing of both liquid and solid materials. Liquid samples were contained in a Teflon tank, while solid samples were arranged on one or more Teflon plates—either as thin layers, cubic blocks, or hemispherical specimens. To effectively couple electromagnetic energy into the cavity, a proposed feeding architecture utilizing two pairs of pyramidal horn feeders was investigated and evaluated against a baseline of conventional rectangular waveguides. Each pair was mounted on adjacent upper sides of the cavity, with orthogonal field orientations to achieve a wide range of polarization diversity and improve field uniformity, while minimizing crosstalk. A comparative analysis demonstrated that the horn-based system provides improved power-loss uniformity and higher power accepted efficiency relative to the waveguide configuration, although residual hot and cold spots remain in both configurations. Ultimately, the primary novelty of this work lies in the synergistic integration of the optimized octagonal geometry, the independent cross-polarized horn feeds, and the specialized Ferris-wheel rotational mechanism. These findings are based on rigorous 3D full-wave simulations within the cavity at $\text{2.45}\text{GHz}$ over a $\text{50}\text{MHz}$ bandwidth using CST Microwave Studio, incorporating a time-averaged Gaussian frequency profile to model realistic magnetron spectral pulling. Furthermore, benchmarking against a horn-fed hexagonal cavity and a slot-fed octagonal cavity highlighted the trade-offs of the proposed design, which achieved the most favorable thermal uniformity among the tested configurations. The power-loss and thermal distributions obtained for Feta cheese highlight the system's potential to achieve efficient heating with improved thermal uniformity relative to conventional feeding approaches.
The growing complexity of wireless communication systems has highlighted the need for innovative methods to optimize the design of passive radiofrequency (RF) networks. This work presents a novel AI-driven methodology for the electromagnetic-free design and optimization of pixelated square-shaped RF filter models. The method relies on 16× 16 binary matrices composed of randomly placed metallic squares and ports, encoded as 18× 18 input grids. To evaluate the impact of physical dimensions on filter behavior, four square sizes were tested, and a dedicated artificial neural network (ANN) was trained for each configuration. A dataset of over 400,000 structures was generated using automated electromagnetic (EM) simulations. These data were used to train a deep ANN capable of predicting S-parameters with high precision. The trained models achieved a coefficient of determination ($R^{2}$) scores ranging from 0.7872 to 0.9636 and mean squared errors (MSE) between 0.0491 and 0.008. Therefore, the best model exhibiting the highest predictive performance was selected for subsequent optimization. To enable efficient optimization, a genetic algorithm (GA) was implemented using the ANN as a fast surrogate evaluator. This strategy reduced computation time drastically, achieving valid filters designs in less than 60 minutes. The results demonstrate that the proposed approach enables the synthesis of high-performance passive RF structures without relying on time-consuming EM simulations, opening a path toward rapid and scalable design workflows in the RF domain. The proposed layouts present non-traditional geometries, providing alternative design configurations that can effectively satisfy demanding bandwidth and matching specifications, usually difficult to attain through conventional design methodologies.
This paper presents a spacecraft designed to demonstrate and mature essential technologies for a future solar power satellite (SPS). This spacecraft, “Arachne”, hosts a flexible 2-m2 solar-to-RF phased array – the first of sufficient size to allow for a controlled study in low-earth orbit (LEO) on the effect of structural deformation on the array's 2-D radiation pattern. The 2-m2 transmit array is composed of nine solar-to-RF tiles that directly convert sunlight to an X-band microwave beam. These tiles mount to an articulating panel able to impart controlled deformation representative of flexure in superscale space-based phased arrays. Ground testing verifies that the phased array is able to correct for deformation-induced distortion in the shape of the microwave beam based on sensor readings of the array's surface profile. The spacecraft's intended in-orbit mission objective is the demonstration of solar-to-RF conversion and beam control from a flexible surface over a matrix of illumination conditions, beam pointing angles, and surface deformation states. A detailed experiment plan is presented for measuring the 2-D radiation pattern of a flexible phased array operating from LEO. The intent of Arachne is to address key technical risks associated with the challenge of beamforming using a dynamically deforming phased array. Although, at the time of this publication, the Arachne phased array payload is launch-ready, the success of the ground testing is allowing the project to bypass on-orbit experimentation with the current phased array payload in order to accelerate the allocation of resources toward the development of a follow-on prototype addressing additional technical requirements for breakthrough RF efficiency and thermal performance. The development of Arachne, its associated experiment plan, and our continuing efforts, are shortening the timeline to a future superscale SPS constellation capable of powering remote installations and forward operating bases (FOBs).
