Magnetless RF Isolator Design Using Grounded Transistors

Isolators are a fundamental component of many radio frequency (RF) communication systems. Typical RF isolators are obtained using permanent magnets that drive a static magnetic field through ferromagnetic materials inducing non-reciprocal propagation through the medium. Magnetless isolation has been proposed in a number of recent publications to allow integration of these components and also avoid the use of strong magnetic fields. In the magnetless approach, non-reciprocity is achieved through spatiotemporal modulation of circuit parameters. In this paper, we present the base theory and design approach for magnetless isolators using grounded transistors. We present a magnetless isolator design with 20 dB isolation and 3 dB insertion loss at a frequency of 2.1 GHz.