arXiv subjects

Daniel F. Sievenpiper

Publications and source records attributed to Daniel F. Sievenpiper.

22 records · Page 2Linked to original sources

arXiv2019

Waveform Selective Surfaces

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, we demonstrate a new kind of microwave window that has the unique property of controlling transmission and reflection based not only on the frequency of an incoming wave but also on the waveform or pulse width. 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 only possible by introducing nonlinear electronics into the surface. Thus, our 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.

physics.app-ph↗

arXiv2017

Guiding waves along an infinitesimal line between impedance surfaces

We present a new electromagnetic mode that forms at the interface between two planar surfaces laid side by side in free space, effectively guiding energy along an infinitesimal, one-dimensional line. It is shown that this mode occurs when the boundaries have complementary surface impedances, and it is possible to control the mode confinement by altering their values correspondingly. The mode exhibits singular field enhancement, broad bandwidth, direction-dependent polarization, and robustness to certain defects. As a proof-of-concept, experimental results in the microwave regime are provided using patterned conducting sheets. Our proposed effective-medium-based approach is general, however, thus allowing for potential implementation up to optical frequencies. Our system is promising for applications including integrated photonics, sensing, switching, chiral quantum coupling, and reconfigurable waveguides.

cond-mat.mes-hall↗

arXiv2015

Waveform Selectivity at the Same Frequency

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 the circuit elements are then combined to absorb or transmit specific waveforms in between. This waveform selectivity gives us another 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 waveforms.

physics.optics↗

arXiv2014

Waveform-dependent absorbing metasurfaces

We present the first use of a waveform-dependent absorbing metasurface for high-power pulsed surface currents. The new type of nonlinear metasurface, composed of circuit elements including diodes, is capable of storing high power pulse energy to dissipate it between pulses, while allowing propagation of small signals. Interestingly, the absorbing performance varies for high power pulses but not for high power continuous waves (CWs), since the capacitors used are fully charged up. Thus, the waveform dependence enables us to distinguish various signal types (i.e. CW or pulse) even at the same frequency, which potentially creates new kinds of microwave technologies and applications.

physics.optics↗