Abstract
In this paper, we proposed a dynamic modulation band rejection filter based on the spoof surface plasmon polaritons (SSPPs) waveguide. The dynamic adjusting mainly derives from changing the capacitance between the U-shape and the waveguide configuration. The capacitance can modulate the cut-off frequency of fundamental mode. The rejection band is formed by the high order propagation mode and the cut-off frequency of fundamental mode. We analyzed the dispersion curve and transmission performance of the band rejection filter with different capacitances. Compared with the previous scheme, the design we proposed here has a simpler and more delicate configuration to process and decreases the mechanical error. We experimentally demonstrated the excellent performance of the device by changing the direct voltage loaded on the varactor diode and achieved real time modulation around 2 GHz.
Highlights
As a kind of special surface wave, surface plasmon polaritons (SPPs) exist at the interface of metal and dielectric, which propagate along the interface and attenuate exponentially in the direction of normal interface [1,2,3]
It had been proven that the SPPs have the ability to confine and enhance the near electromagnetic field, so they will bring a lot of innovative technologies and applications, such as subwavelength focusing [4,5,6], subwavelength imaging [4,5,7], biosensing [8,9,10,11], harmonics generation [12,13], photonic integrated circuit and waveguide [6,14,15,16,17]
A simpler method to fabricate a dynamic modulation band rejection filter device loaded with varactor-diodes has been proposed and manufactured
Summary
As a kind of special surface wave, surface plasmon polaritons (SPPs) exist at the interface of metal and dielectric, which propagate along the interface and attenuate exponentially in the direction of normal interface [1,2,3]. To apply SSPPs devices in practice, conformal surface plasmon constructions on planar flexible films have been proposed, which can propagate the spoof SPPs in the form of a bent and spiral shape [22]. It is a promising solution for spoof SPPs to apply in future microwave integrated circuit regions [23]. Tracing previous researchers’ thoughts [27,35,36], here we proposed an active modulation band rejection filter through controlling the cut-off frequency between the fundamental mode and the high order mode, which arises from changing capacitance generated between the waveguide and U-shape ring. The filter we present here has a simpler configuration that makes the sample easier to produce and decreases the mechanical error to some extent, compared with the former design [27]
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