I. Introduction
Devices with non-reciprocal transmission (gyrators, isolators and circulators) are often required in wireless communications and radar/imaging sensors. There has been a recent surge in research to realize integrated CMOS non-reciprocal components that do not rely on magnetic (ferrite) materials [1]-[6]. Techniques that have been explored include varactor modulation in resonant rings [1], switched-capacitor N-path filter approaches [2], [3] and switched-transmission-line approaches [4], [5]. While these efforts have been successful in enhancing linearity and power handling [5], their bandwidths and frequency tunability have been limited to a fraction of the center frequency and their footprints have been large due to the use of LC resonators or wavelength-scale transmission lines.