Layout of the fabricated topological heterostructure prototype, based on a microwave printed circuit board (PCB) with surface-mount circulators and TLs (left). The reconfigurable region is highlighted by a dashed box. Right: Zoomed-in view of a tunable scatterer implemented with TL-integrated split-ring resonators, a low-pass (LP) filter, and a varactor diode whose capacitance is controlled by a DC bias voltage fed from the other side of the PCB. A one-to-one correspondence exists between the varactor capacitance and the scattering strength .
