Reactive Impedance Substrate Research Articles

Metamaterial Loaded Circularly Polarized Fractal Antenna for 2.4 GHz Frequency Applications

A metamaterial loaded circularly polarized fractal boundary patch antenna is investigated for applications at the ISM band. The suggested patch comprises of Minkowski fractal over metamaterial inspired reactive impedance substrate. Initially, asymmetrical Minkowski fractal curves are deployed at the edges of a square patch for generating the circular polarization (CP). Later, using metamaterial reactive impedance substrate as antenna loading, CP bandwidth is enhanced. The characteristics of the Minkowski fractals are adjusted to obtain the pure CP radiation. The metamaterial loaded Koch fractal antenna is also studied for CP emission. Minkowski antenna with fractal reactive impedance surface as metamaterial with iteration 1 is experimentally examined. The achieved 10-dB return loss and 3-dB axial ratio bandwidths are 40.7% and 7.47%, respectively.

Dual-Band Circular Polarized Flexible Implantable Antenna Using Reactive Impedance Substrate

This communication presents a compact wideband implantable loop antenna with circular polarization (CP) characteristics at 920 MHz industrial scientific and medical (ISM) (902–928 MHz) band and 2.45 GHz ISM band (2.40–2.48 GHz). To widen the impedance bandwidth (IBW) and improve the axial ratio (AR) behavior of the antenna, a reactive impedance substrate (RIS) is exploited. Meandering each arm of the loop makes the antenna compact in size, while the generation of surface wave by the RIS and open-ended configuration of the antenna collectively renders circular polarized wave. The performance of the antenna is analyzed using a single-layer skin model and other existing phantom models. The key feature of the proposed antenna is its dual-band CP behavior, which persists even at the flexion deformation of the human skin. An IBW of 123% with a 3 dB AR bandwidth of 15% and 8.7% is obtained at the planar state of the skin implantable antenna. To validate the simulated results, in vitro measurements were experimentally performed. Also, to find the maximum transmission range of the antenna for biotelemetry communication, the link margin has been analyzed. Finally, to use the antenna inside the biomedical device, the effect of microelectronic components is investigated.

Antenna with a reactive impedance substrate for mine rescue applications

Antenna with a reactive impedance substrate for mine rescue applications

Wideband THz antenna using graphene based tunable circular reactive impedance substrate

This letter presents a graphene–based tunable circular reactive impedance substrate (G–CRIS) operating at THz frequency. The proposed RIS is composed of sectoral graphene patch elements, arranged in two concentric rings and printed over silicon dioxide layer which is backed by a thin gold layer. The reactive behavior of the CRIS is made tunable by applying different chemical potential on graphene patches. This tunable CRIS is employed further to improve the operational bandwidth of a THz antenna. The CRIS loaded antenna exhibits miniaturized resonance at the lower band and wideband characteristics at the upper band. Both gain and efficiency of the antenna have been studied throughout the operating band. It is found that at THz frequency this graphene–based RIS is more suitable than metallic RIS for controlling the operational bandwidth.

Miniaturization of a patch antenna using circular reactive impedance substrate

In this article, to construct a reactive impedance substrate, unit ring is designed and proposed with radial and concentric mode analysis. A cylindrical substrate backed with a PEC plane and circular metallic elements on the top is used for achieving reactive surface impedance behavior. In this aspect, three unit rings structure with different ring elements are designed and simulated to realize the reflection phase characteristics. Afterwards, a probe-fed circular patch antenna is miniaturized by stacking the three-ring circular reactive impedance surface. The fundamental resonance frequency of the proposed antenna is reduced by about 30% with an improvement in impedance bandwidth by 121.6%. An improved front-to-back ratio as well as an acceptable co-pol and cross-pol isolation is exhibited in both E-plane and H-plane at the resonance frequency. In addition of miniaturization, dual band behavior has also been observed in the proposed design. Both resonance phenomena have been explained by circuit model representation and surface current distribution analysis. Improved radiation efficiency at 81.5% has been measured for the proposed antenna configuration.

Compact circularly polarized conical‐beam antenna based on the reactive impedance substrate

ABSTRACTA compact circularly polarized (CP) conical‐beam antenna based on the reactive impedance substrate (RIS) is proposed in this work. This single‐fed antenna utilizes a small circular patch and six curved branches as primary radiators. For the miniaturization purpose, the RIS structure is used, and an overall volume of only 0.66λ × 0.66λ × 0.066λ with respect to 5 GHz is achieved. For experimental demonstration, the proposed antenna is fabricated and tested. Acceptable agreements are obtained between the measured and simulated results. The antenna peak gain at the center frequency is 3.3 dBic and occurs at θ = 48°. Moreover, good omnidirectional CP feature is obtained. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:240–243, 2017

New Metrics for Artificial Magnetism From Metal-Dielectric Metamaterial Based on the Theory of Characteristic Modes

In this letter, new metrics are proposed to provide physical insight into the behavior of metamaterial-based structures by means of the theory of characteristic modes. A relationship between the first eigenmode and an expression of the polarizability is proposed for a split-ring resonator. It thus allows us to describe a link between the artificial magnetic response of a split-ring resonator and modal characteristics. Using the new metrics proposed, a reactive impedance substrate based on metal-dielectric metamaterial excited by a parallel magnetic field is shown to exhibit artificial magnetism. These metrics are shown to propose good agreement with other analytical and numerical methods. This analysis should be useful when such metal-dielectric metamaterial structures are associated to radiating elements like antennas since it could be performed in the near-field region, unlike common approaches based on plane wave and far-field assumptions.

Wideband Circularly Polarized Patch Antennas on Reactive Impedance Substrates

A reduced-size wideband single-feed circularly polarized patch antenna is introduced for telemetry applications in S-band around 2300 MHz. The proposed structure consists of a slot-loaded patch antenna printed over an optimized metamaterial-inspired reactive impedance substrate (RIS). We demonstrate, step by step, the main role of each antenna element by comparing numerically and experimentally the performance of various antenna configurations: antenna over a single- or dual-layer substrate, standard patch or slot-loaded patch, antenna with or without RIS. The final optimized structure exhibits an axial-ratio bandwidth of about 15% and an impedance bandwidth better than 11%, which is much wider than the conventional printed antenna on the same materials.