Fig. 1. String-level shutdown device. (a) Schematic drawing 1; (b) schematic drawing 2

Fig. 2. Design scheme diagram of panel-level shutdown system

Fig. 3. Hardware physical diagram

Fig. 4. Cyclic sequence diagram

Fig. 5. Program flow chart. (a) Main program flow chart; (b) program flow chart of timer interrupt

Fig. 6. Serial port between AD9837 and MCU

Fig. 7. Modulated signal. (a) Starting code sequence; (b) stopping code sequence

Fig. 8. Schematic of phase-locked demodulation

Fig. 9. Demodulated signal. (a) Starting code sequence; (b) stopping code sequence