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We investigate using a reconfigurable metamaterial structure based on high permittivity dielectric elements in a flexible origami framework to control the electromagnetic response of a suspended patch antenna. Origami-inspired dielectric structures are fabricated by additive manufacturing of origami elements using an ABS-30 vol% BaTiO3 filament (permittivity ${\sim }11$ ). The printed millimeter-scale elements are then assembled into an origami structure using flexible polymer hinges. Alternatively, dielectric origami structures are also achieved using a flexible, polymer-only origami lattice pre-fabricated by stereolithography into which shaped high dielectric elements (permittivity ${\sim }18$ ) of ABS-60 vol% CaTiO3, manufactured by field assisted sintering, are inserted. The various dielectric origami designs are inserted into the air gap between a suspended patch antenna and a ground plane, designed to operate at a resonant frequency of 1 GHz. The presence of the dielectric origami modifies the antenna resonant frequency and tunablity is then achieved through different configurations of the dielectric origami, actuated by hand or mechanically. Tunability arises because varying the configuration, and overall density, of the dielectric origami varies its effective permittivity and thus the patch resonant frequency. The dielectric origami structures provide a tunable range up to ${\sim }14\%$ , in good agreement with numerical simulations. Simulations are also used to show how broader tunability could be achieved easily, for example, by optimizing the size of the dielectric elements. Overall, the results using these preliminary dielectric origami structures, enabled by combining advanced manufacturing techniques, suggest that the approach offers a wide design space with the potential to realise novel antenna functionality and flexibility.

This paper presents the design and synthesis of a low-loss substrate with low effective permittivity (εeff ) for microwave and mm-Wave applications. The proposed design is based on the two-phase Maxwell Garnet mixing theory, where the εeff of the RF substrate can be synthesized depending on the geometry and the permittivity of mixing particles and the permittivity of the host material. A comprehensive review and error analysis of the most common mixing techniques are conducted to guarantee an accurate design for high-performance RF substrates. Several analyses based on the geometries of various particles are carried out to identify the most accurate mixing model used in the design of the proposed substrate. The effects of the direction of excitation as well as the polarization of the incident field on the εeff of the anisotropic particle are analyzed and discussed. The proposed method enables the use of existing high-performance materials that do not necessarily provide a low dielectric constant and low loss tangent. For mm-Wave antenna applications, materials with a dielectric constant of 2-4, and loss tangent of less than 0.002 are desirable to maximize gain and radiation efficiency. Commercial RF substrates can satisfy those requirements, however limited thermal expansion coefficient and lamination difficulties increase the cost significantly. The proposed method enables the use of inexpensive materials that provide excellent thermal properties and great compatibility with a multi-layer fabrication process with desirable εeff and loss tangent. For validation of the analysis, samples are fabricated and tested in the microwave frequency (S-band) at 3.5 GHz as well as in the mm-Wave frequency (W-band) at 77 GHz. Measured results show a reduction of 45% in the εeff and 38% in the loss tangent values in the S-band, and 32% and 72% reduction in εeff and tanδ, respectively, in the mm-Wave frequency band. The measured results are in excellent agreement with the simulation and calculated results.

A new novel structure is proposed for cellular composite radar absorbing materials, and an equivalent method of electromagnetic scattering for the new material is also proposed for the first time. By covering the target surface with non-uniform medium cellular cell elements horizontally, the scattering characteristics of the coated target show strong surface anisotropy, leaving an imaginary space for optimizing the electromagnetic stealth performance of the coated target. In this paper, the equivalent dielectric tensor of horizontal directional composite honeycomb cell element has been calculated by using the equivalent method of electromagnetic scattering based on strong fluctuation theory (SFT) of anisotropic medium. Under the condition of plane wave irradiation with a frequency of 3 GHz, we use FEKO software to estimate the backscatter field of several typical models coated with this new structure. It has been proved that the strong fluctuation theory applied to the honeycomb composite absorbing material of the structure are effective for calculating the equivalent scattering. Based on the validity of the equivalent results, we further estimate the scattering characteristics of complex targets coated with the novel cellular medium.

This paper explores the effective temporal surface-illuminated properties of two-component composites consisting of inclusions of regularly-and irregularly-shaped crystals in a matrix. Time-domain electromagnetic modeling using the finite integration technique is used to calculate scattering (S-) parameters, and from these, the effective relative permittivities are calculated. It is shown that the orientation of inclusions with high permittivity contrast affects the effective electrical permittivity of a composite mixture. For both low and high contrast inclusions, fields localize at edges and corners of the irregular inclusion in a manner not dependent on boundary conditions used in simulation.

The electromagnetic (EM) properties of two-component mixtures involving many disordered regularly and irregularly shaped crystals are studied. The effective relative permittivities are calculated utilizing the time-domain finite integration technique. The effective permittivity of disordered mixtures deviates from established mixing theories especially in cases of high permittivity contrast between inclusions and matrix material, and is strongly correlated to the cross-sectional area of the inclusion crystals. Electric energy density localizes at the edges and corners of inclusions in a manner independent of inclusion shape and influenced by EM propagation direction and surrounding inclusions. For mixtures with both disordered irregular and more organized cube inclusions, energy localization increases as the EM signal travels through the mixture before decreasing due to attenuation of the propagating EM signal. With a large number of inclusion crystals (here in the hundreds), it is found that the impact on effective permittivity from differences in individual inclusion shapes is negligible.