Design Essay

I

To Design and Build a Portable, Miniaturised, Multichannel
FM Transmitter

Author
Francis Mc Swiggan
9427406

Supervisor
Dr. Máirtín Ó Droma
University Of Limerick

Course
B. Eng. Electronic Engineering (LM070)

Submitted in part requirement for final year project to
University of Limerick, Limerick, Ireland
28/04/98

Abstract
The aim of the project is to develop a Miniaturised low power FM Transmitter to be
used in specialised applications such as a hearing aid for a tour guiding system and
room monitoring (such as a baby listening device). The overall module should be
miniature to enable portability. Frequency modulation has several advantages over the
system of amplitude modulation (AM) used in the alternate form of radio broadcasting.
The most important of these advantages is that an FM system has greater freedom
from interference and static. Various electrical disturbances, such as those caused by
thunderstorms and car ignition systems, create amplitude modulated radio signals that
are received as noise by AM receivers. A well-designed FM receiver is not sensitive to
such disturbances when it is tuned to an FM signal of sufficient strength. Also, the
signal-to-noise ratio in an FM system is much higher than that of an AM system. FM
broadcasting stations can be operated in the very-high-frequency bands at which AM
interference is frequently severe; commercial FM radio stations are assigned
frequencies between 88 and 108 MHz and will be the intended frequency range of
transmission.
The main report will reflect on 4 issues, background to frequency modulation,
electronics component characteristics, basic transmitter building blocks and finally an
analysis of the finished design as regards construction and performance.

Created by Francis Mc Swiggan
(francis@csn.ul.ie)

II

Declaration

This report is presented in partial fulfilment of the requirements for the degree of
Bachelor of Engineering.

It is entirely...