Because of exhibiting extraordinary features, metamaterial absorbers have captured considerable attention in recent years, especially at visible frequencies. In this paper, a new design of a metamaterial-inspired perfect visible absorber (MIPVA) is investigated, which exhibits ultra-broadband, polarization-independent, and wide-angle performances. The proposed MIPVA provides a flat and near unity absorbance (>99%) in an ultra-broad range of radiation wavelengths from λ=500 to 625 nm, while retaining its convincing absorptivity over the entire visible wavelengths. A comprehensive parametric study is accomplished to demonstrate the effects of structural parameters on the absorptivity of the designed MIPVA. To clarify the physical mechanism of absorption, the electric field and surface current distributions of MIPVA are also monitored and elaborately discussed throughout the paper. The results show that the proposed MIPVA exhibits a polarization-insensitive absorption behavior in a wide range of incident wave angles. The interference theory is also utilized to verify the results. In addition, our MIPVA has a compact and low-profile design, while its ability to absorb solar radiation is significantly improved with respect to preceding studies in terms of both the frequency bandwidth and absorptivity; thereby, it is a worthy candidate to play an essential role in different visible-range applications.

In this study, a reconfigurable triple-band triple-mode substrate integrated waveguide filter is designed and fabricated in the C-band spectrum. A novel and simplified design procedure based on analytical equations is proposed. The filter design also benefits from a reconfigurable structure, using metallic via holes as perturbation, allowing wide-band selectivity of the C-band spectrum (from 4.4 to 6.9 GHz). Moreover, the filter benefits from a magnetic coupling solution between the resonators, which only couples the first three modes and rejects the next resonating modes.Therefore, a large bandgap in the spectrum is achieved. The proposed structure is fabricated and measured, and a high similarity between the simulation and fabrication is observed. The measured results show that the first band can be tuned in the frequency range of 4.4 to 7, the second band can be tuned in the range 5.8 to 7.7 GHz, and the third band from 5.8 to 7.7 GHz. The insertion loss 1.5 to 2.5 dB, 2 to 3 dB, and 2.5 to 3.5 dB for the first, second, and third bands, respectively.

This paper presents a novel single-layer dual band-rejection-filter based on Spoof Surface Plasmon Polaritons (SSPPs). The filter consists of an SSPP-based transmission line, as well as six coupled circular ring resonators (CCRRs) etched among ground planes of the center corrugated strip. These resonators are excited by electric-field of the SSPP structure. The added ground on both sides of the strip yields tighter electromagnetic fields and improves the filter performance at lower frequencies. By removing flaring ground in comparison to prevalent SSPP-based constructions, the total size of the filter is significantly decreased, and mode conversion efficiency at the transition from co-planar waveguide (CPW) to the SSPP line is increased. The proposed filter possesses tunable rejection bandwidth, wide stop bands, and a variety of different parameters to adjust the forbidden bands and the filter’s cut-off frequency. To demonstrate the filter tunability, the effect of different elements like number (n), width (WR), radius (RR) of CCRRs, and their distance to the SSPP line (yR) are surveyed. Two forbidden bands, located in the X and K bands, are 8.6–11.2 GHz and 20–21.8 GHz. As the proof-of-concept, the proposed filter was fabricated, and a good agreement between the simulation and experiment results was achieved.

In this research, a thorough experimental and numerical study is conducted to investigate a novel application of the ultrasonic Lamb waves which is its capability to detect of the coating disbond in a double-layer waveguide (aluminium-adhesive) and a triple-layer waveguide (aluminium-adhesive-coating). The experimental tests are set up and implemented to evaluate how the attenuation of Lamb waves is affected by the adhesive bonding beside the contribution of the coating layer to the behaviour of Lamb waves. The semi-analytical finite element (SAFE) method is employed to analyse and identify the properties of guided wave modes propagating along the coated structures. In the presence of additive white Gaussian noise (AWGN), a range of important indices including energy index (EI), amplitude index (AI), pulse width index (PWI), and the time of flight index (ToFI) are worked out in association with the disbond length. It is inferred that a) even in the very noisy environment of 0 dB SNR, the Lamb waves are effectively able to identify debonding defects particularly using the EI, giving sensitivity rates 105% and 30% for triple-layer and double-layer, respectively; b) the contribution of adhesive to the absorption of the guided wave energy is 30%, 40%, and 50% in EI, AI, and PWI, respectively, corroborating the value of the features to distinguish the debonding between each layer of bonded structures.

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