Waveform selectivity at the same frequency.

Hiroki Wakatsuchi,Fei Gao,Sanghoon Kim,Daniel F Sievenpiper,Daisuke Anzai,Jeremiah J Rushton

doi:10.1038/srep09639

Hiroki Wakatsuchi, Fei Gao + Show 4 more

Open Access

https://doi.org/10.1038/srep09639

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Abstract

Electromagnetic properties depend on the composition of materials, i.e. either angstrom scales of molecules or, for metamaterials, subwavelength periodic structures. Each material behaves differently in accordance with the frequency of an incoming electromagnetic wave due to the frequency dispersion or the resonance of the periodic structures. This indicates that if the frequency is fixed, the material always responds in the same manner unless it has nonlinearity. However, such nonlinearity is controlled by the magnitude of the incoming wave or other bias. Therefore, it is difficult to distinguish different incoming waves at the same frequency. Here we present a new concept of circuit-based metasurfaces to selectively absorb or transmit specific types of waveforms even at the same frequency. The metasurfaces, integrated with schottky diodes as well as either capacitors or inductors, selectively absorb short or long pulses, respectively. The two types of circuit elements are then combined to absorb or transmit specific waveforms in between. This waveform selectivity gives us another degree of freedom to control electromagnetic waves in various fields including wireless communications, as our simulation reveals that the metasurfaces are capable of varying bit error rates in response to different waveforms.

Highlights

Electromagnetic properties depend on the composition of materials, i.e. either angstrom scales of molecules or, for metamaterials, subwavelength periodic structures
Metamaterials[1,2,3], composed of sub-wavelength resonant structures, readily enable us to use negative- or zero-refractive indices[2] as well as artificially engineered high impedance surfaces[3] which allow surface wave properties to be controlled. These unusual properties were applied to the development of a diffraction-limitless lens[4,5], cloaking device[6,7,8], unusually thin absorbers (,l/4 where l is the wavelength of the incoming wave)[9,10,11], etc
In this study we present a new concept of metasurfaces to fully control waveforms, i.e. selective absorption of either short pulses or continuous waves (CWs) as well as absorption or transmission of specific waveforms in between

Summary

Introduction

Electromagnetic properties depend on the composition of materials, i.e. either angstrom scales of molecules or, for metamaterials, subwavelength periodic structures. In this study we present a new concept of metasurfaces to fully control waveforms, i.e. selective absorption of either short pulses or CWs as well as absorption or transmission of specific waveforms in between This new property termed waveform selectivity allows us to distinguish incoming waves in an unusual manner depending on the frequency and on the waveform. Incoming waves have electric field normal to the metasurfaces, which charges the edge of each patch either positively or negatively and generates strong electric field across the gaps (this electric field turns on the diodes) Under these circumstances the capacitor is capable of fully storing the energy of a short pulse during the illumination, and discharges it into the resistor, which dissipates the energy before a short pulse comes in. Selective absorption and transmission demonstrated below are not due to the variation in the bandwidth of the incoming frequency, since the bandwidth of the signals is small compared to that of the surface without any nonlinear elements (e.g. provided that frequency and pulse width are respectively 4.0 GHz and 50 ns as set below, the one cycle is 0.25 ns and corresponds to only a 200th of the pulse duration)

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