Fig. 4: Measurement inside a TEM waveguide to reduce diffraction.

a Illustration of measurement setup. b Picture of measurement setup. c Picture of the prototype. d The measured transmission rate (T) under different propagation direction. Red line: forward incidence for 2.05 GHz. Blue line: backward incidence for 2.05 GHz. Red shaded area: forward incidence from 2.02 GHz to 2.06 GHz. Blue shaded area: backward incidence from 2.02 GHz to 2.06 GHz. e The measured nonreciprocity (NR). Solid line: 2.05 GHz. Shaded area: 2.02 GHz to 2.06 GHz.