Optical illusion has always attracted extensive attention, as it provides a superior self‐protection ability for both natural animals and human beings. A decade ago, this motivated the study and ...application of transformation optics, which provides a universal tool to manipulate light for invisibility cloaking and optical illusion. However, mainstream transformation‐optics‐based optical illusions are inherently hindered by the extreme requirements of metamaterial compositions in practice and unfavorably limited by the very large computational cost caused by their bulky state. To overcome these grand challenges, a novel and intelligent optical illusion supported by form‐free metasurfaces via a deep learning architecture is reported, which can not only render a similar illusion effect but also greatly reduces the parameter space in physics. Illustrative examples of conformal metasurfaces are presented, with a high‐fidelity inverse design from either the near‐ or far‐field in the simulation and experiment. Furthermore, a full set of intelligent systems is developed to benchmark the real‐world optical illusion applicability. The work brings the available illusion strategies closer to a wide range of in situ practical‐oriented applications and lays a foundation for the next generation of intelligent metamaterials.
An in situ intelligent optical illusion is demonstrated via a global metasurface reconstruction strategy. The intelligent optical illusion not only creates a customer‐defined illusion effect, but also greatly simplifies the mainstream but hard‐to‐reach transformation optics‐based methodology. Illustrative examples of conformal metasurfaces with high‐fidelity inverse design are presented, and a full set of intelligent systems is built to benchmark the real‐world illusion applicability.
Recently, localized spoof surface plasmon polaritons (LSSPPs) have emerged as a new research frontier due to their unique properties and potential applications in integrated circuits. The toroidal ...dipole is a localized electromagnetic response different from electric and magnetic dipoles. Anapole is the nonradiating source produced by the interference between identical radiation patterns of toroidal and electric dipoles in the far field. This paper proposes a novel high Q‐factor compact planar resonator consisting of split‐ring resonators to support the LSSPPs anapole at microwave frequency, which shows an apparent nonradiating charge–current configuration. In simulation and measurement, we observe the nonradiating property of the anapole mode. Further, we demonstrate that the LSSPPs anapole resonance has the tunable property, which is very sensitive to structural changes. These might lead to potential applications in the design of plasmonic deformation sensors, cloaking, and absorbers.
This paper presents a robust nonlinear control strategy to solve the instability problem of dc-dc buck power converter with a constant power load in dc microgrid systems. Based on the passivity-based ...control (PBC), a nonlinear disturbance observer (NDO) is designed to improve the control robustness against both load and line variations, whereas the PBC guarantees the system stability due to its property of transient energy dissipation. By applying the disturbance estimation technique, NDO works in parallel with the PBC controller to compensate the disturbances through a feed-forward channel. This strategy ensures large signal stability as well as fast recovery performance of the system during disturbance/uncertainty as compared to other nonlinear control methods. Hardware-in-loop (HIL) experiment is performed on an OPAL-RT real-time simulator. MATLAB simulation and HIL results are provided to verify the proposed control strategy. Further validations are presented using a real hardware experiment to emphasize the robustness of the proposed controller.
This article presents a new optimization method for complex power distribution networks (PDNs) with irregular shapes and multilayer structures using deep reinforcement learning (DRL), which has not ...been considered before. A fast boundary integration method is applied to compute the impedance matrix of a PDN structure. Subsequently, a new DRL algorithm based on proximal policy optimization (PPO) is proposed to optimize the decoupling capacitor (decap) placement by minimizing the number of decaps while satisfying the desired target impedance. In the proposed approach, the PDN structure information is encoded into matrices and serves as the input of the DRL algorithm, which increases the flexibility of the method to be extended and generalized to different PDN configurations. Also, the output of the algorithm determines the selection of decap types and locations collaboratively, making it easier to find the optimal solution in a huge search space. The proposed method is compared with the state-of-the-art approaches and shows consistent advantages in reducing the number of decaps in different testing cases.
This article presents a novel four-port symmetric probe calibration method for on-wafer S-parameter measurement, where by using the symmetric property of the probes, the four-port calibration process ...is greatly simplified while maintaining a high calibration accuracy. Only four measurements with four different calibration standards are needed in the proposed calibration process, including open, short, load, and thru. Furthermore, only the phase sign is needed for the thru standard rather than its precise S-parameters. The proposed calibration method coupled with an optimization approach is developed to obtain the parasitic parameters of the open, short, and load standards. The proposed method can consider the crosstalk between the probes and move the calibration reference planes to the probe tips. The accuracy of the proposed method is validated in an on-wafer S-parameter measurement system with both ground-signal-signal-ground (GSSG) and ground-signal-ground-signal-ground (GSGSG) probes up to 50 GHz.
Frequency-selective surfaces (FSSs) are widely employed in antenna's radar cross-sectional reduction, which plays a key role in improving survivability and penetration ability of future military ...systems. In practical, dual-band bandpass FSSs with large band ratio (BR) are urgently needed for some military equipment, such as homing head, that can detect both middle and far range targets. In this paper, a novel method for designing dual-band bandpass FSS with large BR is proposed. The method can provide a large BR response, by utilizing a spurious-free structure and combing resonant and nonresonant elements. The detailed analysis is presented with the aid of equivalent circuit model as well as closed-form equations to reveal the operating mechanism. A design example is simulated, fabricated, and then measured. Two excellent passbands are obtained with a large BR value of 15.3 in experiment. Moreover, a −10 dB fractional bandwidth of 164.3% is realized from 1.31 to 13.35 GHz, without observing any spurious transmission windows. In conclusion, our proposed method fills the gap of the existing dual-band FSSs to obtain a large BR value of more than 6 and could be a good guidance for designing the future multiband FSSs.
In this paper, an amplitude and frequency tunable coherent perfect absorption (CPA) is presented using a varactor-embedded frequency selective surface (FSS)-based metamaterial absorber. The proposed ...structure mainly incorporates two dielectric layers, two metal-patterned layers equipped with varactors and resistors, and an intermediate metal cross layer for electrical connections. This coherent absorber is evaluated based on full-wave simulations. When a single electromagnetic wave is incident vertically from one side of the structure, two adjacent peaks are produced with absorption efficiencies of about 50%. The structure is then positioned in the standing wave field created by two counter-propagating coherent waves, where the two peak amplitudes can be selectively enhanced or weakened by adjusting the phase difference between the coherent waves. Moreover, by modulating the reverse voltage across the varactors, the capacitance of the varactors is altered, thereby enabling the tunability of the absorption frequency. Two coherent absorption peaks with phase differences of ϕ = 0° and ϕ = 180° are deliberately designed to be significantly enhanced within distinct frequency ranges. As a result, a CPA with a wide tunable frequency range within 2.3-6.6 GHz is synthesized, where the absorption rates of 2.3-3.8 GHz and 4.25-6.59 GHz exceed 90%. To substantiate the soundness of our theory and design, an equivalent circuit model is constructed, and experimental measurements are also carried out. All the results agree well with each other.
This article presents an uncertainty analysis method for the 16-term error model, and applies the methodology in determining the best calibration standard combinations and their associated parasitic ...parameters. This article proposes a sensitivity analysis method using the complex-valued matrix differentiation to tackle the complexity of the 16-term error network, and the uncertainty propagation is further derived by the properties of the covariance matrix. A novel methodology is additionally proposed for calibration standard selection by combining the uncertainty analysis method with a parasitic-parameter extraction approach. The newly proposed methodology jointly determines the best combinations of calibration standards and their corresponding parasitic parameters and enhances the calibration accuracy and reliability of the 16-term error model. The effectiveness of the technique is validated by on-wafer measurements.
We present a single-layer, transmissive metalens for focusing the orthogonal polarization components of incident light to two independent focal spots without affecting the initial orthogonal ...polarization states. To produce the required phase profile, the cross-shaped nanorod, as the unit cell of the metalens, is developed to support arbitrary combinations of two independent phase shifts (0-<inline-formula> <tex-math notation="LaTeX">2\pi </tex-math></inline-formula>) of transverse electric and transverse magnetic polarized light. A deep neural network is trained to generate the design parameters of each unit cell efficiently and accurately. The metalens is simulated with finite-difference time-domain method and good agreements are observed comparing with theoretical prediction. This work provides a new solution to multi-foci metalens and polarization beam splitter and may find potential applications in deep sensing, holography, information encryption and display.
This study designed a resistive film absorber (RFA) with > 90% absorptivity in the 16-27 GHz broadband to reduce electromagnetic radiation in on-board chip architectures. The size of the RFA unit is ...miniature, which is only 0.1λ L × 0.1λ L × 0.06λ L (where λ L is the lowest operating frequency cutoff wavelength). First, the impedance matching and loss principle of the RFA are analyzed based on the intrinsic parametric method and equivalent circuit theory. This explains the influences of each parameter on absorption performance and verifies that the designed RFA has good polarization insensitivity and angle stability. In addition, the measurements of a prototype RFA were obtained and found to be consistent with simulation results, which proves the feasibility of the RFA. Finally, the RFA was added to a chip architecture to verify its electromagnetic suppression effect with consideration of the influence of temperature on absorption performance. The combined simulation results indicate a significant reduction in the far-field radiation values of the chip architecture, with the maximum electromagnetic radiation suppression effect being 12 dB. These results demonstrate the reliability of the proposed electromagnetic suppression scheme and indicate that the RFA has wide application prospects for radiation suppression in chip systems and electronic packaging.
