Design and implementation of baseband digital adaptive FM demodulator

Abstract

With the advent of technology, the communication has been majorly into digital domain, the modulation and demodulation schemes are mostly implemented in this domain. Also, the systems are designed to be versatile in such a way that they are capable of adapting to various changes in terms of the modulation schemes, data rates and various other pa­rameters. In this paper, the base-band digital FM demodulator is implemented and designed to be adaptive to selective carrier frequency, frequency sensitivity and variable message frequency. FM modulation is implemented using the concept of direct method with the help of numerically controlled oscillator (NCO). Demodulation is implemented using the concept of indirect method which employs digital phase locked loop (DPLL).The Loop Filter is designed on a Microcontroller (Arduino Due 32 bit ARM) while the Phase Detector and the NCO parts of the DPLL are designed and implemented on FPGA to make the system adaptive. Such demodulators are used in satellites for Telemetry and Telecommand subsystems.