Surface plasmon polaritons (SPP) are highly localized surface waves at the interface between metal and dielectric in the optical frequency band. SSPs do not occur naturally in microwave and terahertz frequencies, so “spoof” surface plasmon polaritons (SSPPs) are needed for operations in these lower frequency bands.
Like optical SPPs, microwave SPPs exhibit highly localized electromagnetic fields, subwavelength resolution, and extraordinary field confinement. Therefore, SSPP (TL) transmission lines have been proposed as new types of microwave guides which provide novel solutions for miniaturization, signal integrity and low crosstalk in compact circuits for use in wireless communications. wire and wearable electronics.
Recently, a research team from Southeastern University in China applied a typical form of superior symmetry called “sliding symmetry” in dual-band TPMS TLs to achieve flexible control of modal fields, dispersion characteristics. and mutual coupling between TLs. As stated in Advanced photonics, they built a hybrid TL array with a non-slip symmetrical TL and a slip symmetrical TL, in which a half-period misalignment is observed between the upper and lower bands. Expanded working bandwidth resulted from the slip symmetric TL, and the team demonstrated that slip symmetry helps suppress channel crosstalk significantly without requiring additional space or powering networks.
In their experimental demonstration, the fundamental mode cutoff frequency goes from 5 GHz (for a symmetrical TL without slip) to 9.5 GHz (for a symmetrical TL with slip). Because the fundamental mode of the slip symmetric TL is totally different from that of the non-slip TL, the coupling coefficient between them is significantly lower than that between two uniform TL SSPP. The team noted that due to the mode mismatch in the hybrid grid, a very limited portion of the power could be coupled to the neighboring TL.
Tie Jun Cui, professor at the Institute of Electromagnetic Space at Southeastern University, remarks: “Slip symmetry offers powerful and flexible control of TPMS and may provide new solutions in future integrated circuits. ” Cui envisions that when severe line-to-line interference damages circuit performance, an alternating arrangement of balanced slip and non-slip TLs can restore and ensure signal accuracy. Cui notes: “No additional space or circuit design is required when the non-slip symmetrical TL is replaced with a slip TL.” This space-saving solution can provide significant improvements to future integrated circuits and systems.
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