Multiband Magnetless Isolators and Circulators With Reconfigurable Bandpass Filtering Capabilities

This article reports on the RF design and practical validation of new classes of magnetless multiband isolators and circulators with reconfigurable bandpass filtering capabilities. They are based on transversal frequency-selective signal paths shaped by frequency-tunable and spatiotemporally modulated resonators. Each path creates a passband that can be independently controlled in terms of frequency and direction of propagation. Thus, the overall network may exhibit 1-to- $K$ frequency-reconfigurable non-reciprocal passbands. The operating principles and schematic of the magnetless and reconfigurable filtering isolator concept are first demonstrated through circuit-based simulations of two- and three-path transversal filtering networks (i.e., two- and three-band networks). The independent modulation parameters of the bands are determined through detailed parametric analyses. Next, the concept is extended to the design of magnetless, multiband filtering circulators. The operating and design principles of the circulator are expounded through a circuit schematic and an ideally simulated dual-band example. For practical demonstration purposes, three lumped-element (LE) prototypes, two isolators, and one circulator, shaped by two or three RF signal paths (i.e., two and three passbands), were implemented at very high frequency (VHF) band. They exhibited a maximum in-band isolation (IS) up to 50 dB. Moreover, a frequency tuning of up to 1.22:1 and change of directionality are achieved.