Highly Linear and Magnetless Isolator Based on Weakly Coupled Nonreciprocal Metamaterials

A novel highly linear magnetless isolator based on weakly coupled nonreciprocal metamaterials is proposed in this article. Nonreciprocal devices, such as isolators and circulators, are widely used in modern microwave, optics. Nowadays, nonreciprocity is exclusively achieved with anisotropic magneto-optic material. Unfortunately, this material needs permanent magnetic bias and is typically bulky, which remains incompatible with technology for integrated circuit. In this article, we reveal that strong isolation can be achieved even under the weak coupling between the transmission line and magnetless nonreciprocal metamaterials (MNMs). Compared with previous magnetless nonreciprocal approaches, in this article, as the wave propagates from port 2 to port 1, the interaction between the incoming wave and nonlinear devices can be neglected due to the weak coupling, yielding low loss (|S
₁₂
| = -1.03dB) and high linearity (P
_1dB
> 17dBm, OIP3= 33.5dBm). As the wave propagates from port 2 to port 1, 36.2 - dB isolation can be achieved under the loop resonance. Furthermore, the frequency reconfiguration of MNMs has been investigated for the first time, leading to broadband and multiband isolators.