A DLL-Based FSK Demodulator for Asynchronous Communications

This paper discusses the use of a delay-locked loop (DLL) to perform frequency shift-keying (FSK) demodulation in asynchronous communication systems. Instead of being part of a more complex architecture, the DLL is here used as a frequency demodulator. Similarly to its phase-locked loop (PLL) counterpart, the DLL-based FSK demodulator tracks the frequency variations of the input signal, providing at the output the demodulated received data. The DLL constitutes an efficient alternative to the PLL for FSK demodulation due to its lower complexity, moderate power consumption, and reliable performance even in the absence of a reference clock. The viability of the DLL as FSK demodulator is verified by means of both behavioral and transistor-level simulations carried out in a $0.13 \mu \mathrm{~m}$ CMOS technology.