Wireless Experimental Determination of Dispersion Curves of Spoof Surface Plasmon Polariton Modes Supported by a Transmission Line

Abstract

Excitation of spoof surface plasmon polaritons (SSPPs) by means of a dipole antenna is considered to experimentally assess the dispersion curves of the two first modes guided by a meandered transmission line (TL). First, simulated dispersion curves bring out even and odd symmetries of the SSPP modes highlighted by magnetic field mappings. Then, a dipole antenna with vertical and horizontal polarization is proposed for generating the even and odd propagation modes by near‐field magnetic coupling, respectively. Experimental validation is carried out with a SSPP TL fabricated on a flexible substrate (Kapton). For each mode, experiments show a pass‐band feature of the transmission between two antennas coupled to the SSPP TL with ripples related to the presence of a standing wave. Finally, the dispersion curves are experimentally achieved using a de‐embedding method applied on the scattering parameters directly measured between antennas without the need of a mode conversion structure. Experimental results are favorably compared with the simulated transmission and dispersion curves.

Embroidered Spoof Surface Plasmon Polariton Transmission Line for Wireless Body Sensor Network

“…We can note that due to the thinness of the textile, the dispersion curves are not sensitive to the permittivity of the substrate. Especially, the same dispersion curves were achieved for an SSPP TL with the same sizes and geometry etched on a flexible substrate Kapton [26].…”

“…The experimental dispersion curves plotted in Figure 2 were assessed by means of a de-embeding method involving scattering parameters measured for two different distances between antennas either vertically-or horizontally oriented [26,28]. As shown in Figure 2, experimental curves fit simulations indicating that the even and odd modes were correctly wirelessly generated by means of vertically-and horizontally oriented dipole antennas, respectively [26]. We can note that due to the thinness of the textile, the dispersion curves are not sensitive to the permittivity of the substrate.…”

“…Finally, the Line‐Of‐Sight (LOS) transmission in free space between antennas were measured when the SSPP TL was removed for comparison. In order to characterise the propagation properties of the SSPP modes, the dispersion curves plotted in Figure 2 were first simulated by using the eigenmode solver of HFSS [26]. The SSPP TL supports two modes below a cut‐off frequency higher than 6 GHz (not shown).…”

“…The SSPP TL supports two modes below a cut‐off frequency higher than 6 GHz (not shown). Here, the mode parity was defined by mapping the magnetic field around the SSPP TL as shown in the inset of Figure 2 with the even (odd) mode corresponding to a symmetric (antisymmetric) field, as commonly considered for SSPP [26]. It is worth mentioning that the symmetric (antisymmetric) magnetic field is produced by currents flowing through the meander‐shaped strips in opposite (same) directions.…”

Wearable Spoof Surface Plasmon Polariton Transmission Line

“…And there is only a downward shift of the dispersion curve when reducing the lateral thickness of a metallic corrugation down to subwavelength scale [8]. In addition, SSPP TLs can be wirelessly excited by near-field coupling using antennas [9] [10]. At last, Wireless Body Sensor Network (WBSN) has interested several applications on healthcare, telemedicine and sport.…”