A Filter-less RMS-based S-FSK demodulation technique for SunSpec rapid shutdown receiver

This paper proposes a SunSpec-compliant receiver system for rapid shutdown application. The design uses a nontraditional RMS-based S-FSK demodulation that avoids the need for filters, making it more suitable for CMOS integration. A Matlab simulation verifies that the receiver is able to decode the two binary FSK signals mark (131.25KHz) and space (143.75KHz) within a bit period of 5.12ms. The demodulator output shows enough voltage separation, which relaxes the next stage (comparators) design. The receiver functionality is verified as per SunSpec testing requirements, including a minimum input signal level of 1.7mV in the presence of adjacent in-band interferer with 17mV voltage level.