Abstract
In this article, a time-modulated transparent nonlinear active metasurface loaded with varactor diodes was proposed to realize spatial electromagnetic (EM) wave frequency mixing. The nonlinear transmission characteristic of the active metasurface was designed and measured under time-modulated biasing signals. The transmission phase can be continuously controlled across a full 360° range at 5 GHz when the bias voltage of the varactor diodes changes from 0 V to 25.5 V, while the transmission amplitude is between −2.1 dB to −2.7 dB. By applying the bias voltage in time-modulated sequences, frequency mixing can be achieved. Due to the nonlinearity of the transmission amplitude and transmission phase of the metasurface versus a time-modulated bias voltage, harmonics of the fundamental mode were observed using an upper triangle bias voltage. Furthermore, with a carefully designed bias voltage sequence, unwanted higher order harmonics were suppressed. The proposed theoretical results are validated with the measured results.
Highlights
The frequency mixer [1,2,3] is instrumental in a wireless communication system
Increasing types of frequency mixers such as passive mixers and active mixers are present in almost every wireless communication electronics system; the frequency mixer for a spatially propagating EM wave, with tantalizing applications in new architecture wireless communication systems [6,7,8], is more elusive
Frequency mixing for a spatial EM wave, referred to as harmonic manipulation, has been researched in [17,23,27,28,29,30] using the time-modulated metasurface
Summary
Nonlinear Active Metasurface for Keywords: nonlinear metasurface; time-modulated metasurface; varactor diode.
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