In recent years, unconventional metamaterial properties have triggered a revolution of electromagnetic research which has unveiled novel scenarios of wave‐matter interaction. A very small dielectric permittivity is a leading example of such unusual features, since it produces an exotic static‐like regime where the electromagnetic field is spatially slowly‐varying over a physically large region. The so‐called epsilon‐near‐zero metamaterials thus offer an ideal platform where to manipulate the inner details of the “stretched” field. Here we theoretically prove that a standard nonlinearity is able to operate such a manipulation to the point that even a thin slab produces a dramatic nonlinear pulse transformation, if the dielectric permittivity is very small within the field bandwidth. The predicted non‐resonant releasing of full nonlinear coupling produced by the epsilon‐near‐zero condition does not resort to any field enhancement mechanism and opens novel routes to exploiting matter nonlinearity for steering the radiation by means of ultra‐compact structures.
The homogenization of a metamaterial made of a collection of scatterers periodically disposed is studied from an asymptotic theory and an optimization algorithm. Detailed numerical results are given for resonant scatterers and the spatial dispersion is investigated. 相似文献
The dispersion relations and impedance expressions for both two-dimensional (2-D)/μ-negative and e-negative transmission line metamaterials, which may be paired to form a virtual image of the object, are presented. Under the conjugate matched condition, the voltage distri-butions inside and outside such paired slabs are derived for a plane-wave excitation. Green's functions corresponding to the voltages by a y directed elementary current source excitation are utilized to computed voltage phase and mag-nitude in all regions. The 2-D plots show that the voltage waves, the propagating waves and the evanescent waves, can pass through the conjugate matched slabs and so sub-wavelength virtual imaging has been achieved. 相似文献
A high directive planar antenna made from a metamaterial superstrate and an electromagnetic band-gap (EBG) substrate has been
investigated. A patch antenna surrounded with EBG structures is used as the radiation source. The CST Microwave Studio is
used for the simulation. The results show that the gain of the antenna with metamaterial is 21.6 dB at the operating frequency
of 14.6 GHz. Compared with the patch feed with the same aperture size but without the metamaterial superstrate, the performance
of the antenna is improved obviously and the gain increases about 12.4 dB. 相似文献
ABSTRACT The asymptotic homogenization method is applied to complex dielectric periodic composites. An equivalence to coupled dielectric problems with real coefficients is shown. This is similar to a piezoelectric problem: an out-plane mechanical displacement and an in-plane electric potential establishing a correspondence principle. Closed-form formulas for the complex dielectric effective tensor in the case of a square array of circular inclusions embedded in a matrix are given. These formulas are written in terms of a real and symmetric matrix which facilitates the implementation of the computational scheme. We also get similar formulas for multilayered complex dielectric composites. The real closed-form formulas are advantageous for estimating gain and loss enhancement properties of active and passive composites in certain volume fraction intervals. Numerical computations are performed and the results are compared with other approaches showing the usefulness of the obtained formulas. This may be of interest in the context of metamaterials. 相似文献
In this paper, a novel compact wide-band bandpass filter (BPF) with a wide frequency range is presented. This filter consisting of a multi-mode resonator (MMR) and four metamaterial unit-cells benefits from a very compact size. Unit-cells based on a complementary spiral resonator (CSR) including a metallic via, improve both upper and lower stopband rejection and compensate the insertion loss (I.L) within the passband altogether. This wide-band filter presents a 3-dB bandwidth of 7.7 GHz, ranging from 3 GHz to 10.7 GHz and the Insertion loss is less than 0.7 dB over the passband. The measured results are in good agreement with both the full-wave electromagnetic simulation and the proposed circuit model results. The dimension of the fabricated filter is 0.128 λ × 0.1 λ (i.e., 5.6 × 4.4 mm2). This filter is considerably compact compared to the other wide-band bandpass filters with the same substrate. 相似文献