Fig. 1. The four-level system of Cesium Rydberg atoms
(a): Four-level system diagram of cesium atom; (b): The hyperfine energy levels of 6S_1/2, 6P_3/2, 51D_5/2 and 52P_3/2. 52P_3/2 state is shown above the 51D_5/2 state for simplicity

Fig. 2. The scheme of experiment setup
The red and green arrows in fig.(a) respectively indicate the propagation direction of the probe and coupling laser, and their polarization vector correspond to the red and green arrows in the coordinate axis respectively; P represents the propagation direction of microwave electric field, and its polarization direction is shown by the purple arrow on the coordinate axis. β is the angle between two laser beams and the polarization direction of microwave electric field. α in fig.(b) is the angle that the label rotates anticlockwise

Fig. 3. EIT-AT spectra
(a): EIT transmission signal without microwave electric field; (b): The EIT-AT splitting spectrum when a microwave electric field is applied and β=90°; (c): The EIT-AT splitting spectrum when a microwave electric field is applied and β=0°; P₀, P₁, P₂ and P₃ are the peak heights of each peak in Fig.3, and Δf is the split peak interval of P₁ and P₃

Fig. 4. EIT-AT spectral characteristics change with β
(a): A₁=P₂/P₀; b: A₂=P₃/P₁. When β=0°, A₁=0, and A₂=1; when -90°<β<0°, A₁ decreases, A₂<1; when 0°<β<90°, A₁ increases, A₂>1

Fig. 5. The vector measurement result of near field scattering field of the tag
(a): Simulation result of the commercial finite-difference time domain software CST Microwave Studio; (b): Experimental results