Fig. 1. Principle of KIDs’ detection

Fig. 2. Physical image of typical KIDs

Fig. 3. Principle of homodyne mixing system structure for typical characterization of superconducting KIDs performance

Fig. 4. Schematic diagram of single channel homodyne mixing system circuit

Fig. 5. Setup window for VNA noise measurement in CW mode

Fig. 6. Time domain interface between I and Q channels of VNA

Fig. 7. Schematic diagram of dual channel homodyne mixing system circuit

Fig. 8. Diagram of coordinate rotation formula

Fig. 9. Schematic diagram of IQ mixer calibration complex frequency domain

Fig. 10. Schematic diagram of cross correlation algorithm for dual channel homodyne mixing system

Fig. 11. The Homodyne mixing system and KIDs setup

Fig. 12. IQ Mixer linear area @ 2 GHz

Fig. 13. IQ linear area @ 4 GHz

Fig. 14. IQ Mixer linear area @ 6 GHz

Fig. 15. IQ Mixer linear area @ 8 GHz

Fig. 16. S₂₁ of KIDs measured by homodyne mixing system

Fig. 17. Complex frequency domain diagram of KIDs resonance and non-resonance noise

Fig. 18. PSD of KIDs on resonance and non-resonance

Fig. 19. Comparison of resonance PSD between single channel and dual channel homodyne system testing KIDs

Fig. 20. KIDs PSD Test Result Graph Based on VNA

Fig. 21. S₂₁ parameters of KIDs at different temperatures and DA/dT fitting curve

Fig. 22. NEP result of KIDs