An Ultra‐Compact Spoof Surface Plasmon Polariton Transmission Line and Its Signal Integrity Analysis

An ultra‐compact spoof surface plasmon polariton (UCSSPP) transmission line (TL) based on a meander line is proposed, which can achieve almost the same transmission performance as the conventional rectangular‐groove SSPP TL, but the linewidth is greatly reduced by more than 40%. The coupling effect between two UCSSPP TLs in different line arrangements has been well studied, revealing that excellent crosstalk suppression can be achieved when two TLs are arranged back‐to‐back, while strong coupling occurs when they are arranged face‐to‐back or face‐to‐face. The signal integrity of back‐to‐back UCSSPP TLs is analyzed and demonstrated, which shows that the signal integrity can be greatly improved compared with microstrip (MS) TLs. In addition, based on the principle of mode mismatch, MS and UCSSPP TLs are arranged alternately to solve the mutual coupling problem in multi‐line systems. In contrast, benefiting from the strong coupling of face‐to‐face UCSSPP TLs, an ultra‐miniaturized SSPP coupler working at 9 GHz is designed, whose size can be reduced by over 75% compared with conventional MS coupler. The measurement results show good agreement with full‐wave simulations, indicating that the proposed UCSSPP TL has significant advantages in signal integrity and device miniaturization over previously reported SSPP TLs.