FM modulator and demodulator design

As part of a wireless FM Tranceiver

Bachelor thesis (2019)

Authors

J.J. van Vliet Electrical Engineering, Mathematics and Computer Science
G.W. Hardeman Electrical Engineering, Mathematics and Computer Science

Contributors

S.M. Alavi Electronics - EEMCS (supervisor 1)
M. Babaie Electronics - EEMCS (supervisor 1)
M.J. Pelk Electronics - EEMCS (supervisor 1)
M.A.P. Pertijs Electronic Instrumentation - EEMCS (coach)
M. Cvetkovic Intelligent Electrical Power Grids - EEMCS (coach)
Faculty
Electrical Engineering, Mathematics and Computer Science
Copyright: © 2019 Jasper Jacobus van Vliet, Gijsbert Willem Hardeman
Frequency Modulation FM modulator FM demodulator FM tranceiver
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Published Date

01-07-2019

Language

English

Reuse Rights

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Faculty

Electrical Engineering, Mathematics and Computer Science

Abstract

This report details the design and implementation of subsystems within a wireless FM transceiver. All the subsystems will be developed and integrated into a working FM transceiver. The subsystems discussed in this report are the modulator and demodulator. The modulator, on the transmitter side, varies the carrier wave frequency, based on the input audio signal. The demodulator, on the receiver side, can detect these variations and retrieve the audio signal. The modulator is implemented using a voltage controlled oscillator, which is based on the Colpitts oscillator. The input audio signal controls the oscillation frequency by modulating varicaps. The demodulator consists of mixer, amplifier and a slope detector. The amplifier is not discussed in this thesis. The mixer uses a local oscillator to shift the RF input signal to an intermediate frequency. This thesis proposes a mixer integrated into a local oscillator, using only one transistor. The detector is based on a slope detector, which differentiates the FM signal and converts it into an AM signal. The differentiator is implemented using a bandpass filter. The audio signal is retrieved from the AM signal using an envelope detector. The work will be concluded with a display of the complete FM transceiver circuit.