Realizing Equivalent Negative Capacitor and Negative Inductor Using Distributed Parameter Unit Cell of Microwave Transmission Line

ABSTRACT This article presents a passive method for achieving the equivalence of negative capacitors and negative inductors using the distributed parameter unit cell of microwave transmission lines (MTLs), which is not contrary to Foster's reactance theorem. The proposed method not only establishes the equivalence of negative capacitor and negative inductor but also demonstrates the equivalence of negative resonant circuits. In this paper, the network circuits in MTL that can be equivalent to a negative‐value element and its equivalent conditions are introduced. Building on this network circuit, we conduct a theoretical analysis of right‐handed transmission lines, left‐handed transmission lines, composite right‐/left‐handed (CRLH) transmission lines, and dual composite right/left‐handed (D‐CRLH) transmission lines' distributed parameter unit cells, leading to the derivation of equivalent conditions. Based on these findings, a CRLH unit cell utilizing a microstrip line is designed and fabricated. Experimental results indicate that equivalent negative capacitors and negative inductors can be achieved within the frequency range of 3–5 GHz. Furthermore, the relationship between the distribution parameters of the CRLH unit cell and the bandwidth of equivalent negative‐value element is examined, suggesting that the effect of equivalent negative‐value elements in CRLH distributed parameter networks has the potential to extend from microwave and millimeter wave bands to terahertz bands.