Figure 4

Calibration of MW fields’ amplitude, and SNR of atomic superhet at different relative atom numbers \({N}_{\text{a}}\). a). The calibration value (in dB, blue square dot) of local and signal MW fields as a function of interaction length l, and its linear fitting (solid line). b). Autler-Townes (A-T) splitting spectra at different interaction lengths l used to calibrate the MW fields’ amplitude. c). Signal power \({P}_{\text{s}}\) (black square dot), noise power \({P}_{\text{na}}\) (red circle dot), and signal-to-noise ratio (SNR) (blue triangle dot, right Y-axis) of atomic superhet at different relative atom numbers \({N}_{\text{a}}\). \({P}_{\text{s}}\), \({P}_{\text{na}}\), and SNR are measured at a read-out frequency of \(\delta _{s}= 55 \text{ kHz}\). The solid or dashed straight lines are linear fittings of corresponding data. The error bar of data points is the statistical results of five independent experiments