Waveform Selective Surfaces

Abstract

The role of frequency is very important in electromagnetics since it may significantly change how a material interacts with an incident wave if the frequency spectrum varies. Here, a new kind of microwave window is demonstrated that has the unique property of controlling transmission and reflection based on not only the frequency of an incoming wave but also the waveform or pulse width. This is achieved by designing a planar periodic surface with circuit elements including diodes, which convert most of the incoming signal to zero frequency. This surface can preferentially pass or reject different kinds of signals, such as short pulses or continuous waves, even if they occur at the same frequency. Such a structure can be used, for example, to allow long communication signals to pass through, while rejecting short radar pulses in the same frequency band. It is related to the classic frequency selective surface, but adds the new dimension of waveform selectivity, which is possible only by introducing nonlinear electronics into the surface. Thus, the study is expected to provide new solutions to both fundamental and applied electromagnetic issues ranging from traditional antenna design and wireless communications to emerging areas such as cloaking, perfect lenses, and wavefront shaping.

Metasurfaces for efficient digital noise absorption

“…The absorption performance of this structure was numerically tested using a co-simulation method 24 , 28 that integrated an EM solver with a circuit solver (ANSYS Electronics Desktop R18.1.0). This method is well known to have an advantage over a stand-alone EM simulation method from the viewpoint of simulation efficiency and speed, which contributed to facilitating the optimisation process of metasurface absorbers studied here, although EM field distributions cannot be visualised in this method 29 – 32 .…”

Metasurface sensing difference in waveforms at the same frequency with reduced power level

“…1 b,c). Under these circumstances, the diode bridge converts the incoming spectrum to an infinite set of frequency components, although most of the energy appears at zero frequency as the waveform is fully rectified 21 , 23 , 25 . Therefore, by connecting a capacitor to a resistor in parallel within the diode bridge (Fig.…”

“…This is because if the incoming spectrum is fixed, ordinary materials similarly respond to different waves and thus are incapable of distinguishing one signal from another. As opposed to these conventional materials, however, circuit-based metasurface absorbers were recently demonstrated to be capable of absorbing a particular type of incoming wave even at the same frequency by sensing its waveform or pulse width [21][22][23][24][25][26] . Such a waveform-selective mechanism was thus expected to give us an additional degree of freedom to control electromagnetic waves/signals and solve electromagnetic interference issues occurring at the same frequency.…”

Waveform-Selective Mantle Cloaks for Intelligent Antennas

“…To induce this unconventional waveformselective effect capacitor-based or inductor-based lumped elements circuit are exploited. Moreover, the possibility to exploit more complex circuit based on active elements, such as jFET [42], provides additional design flexibility in electromagnetic problems, enabling new kinds of microwave applications.…”