ES128 MODULE 2a.pdf

BENGUET STATE UNIVERSITY COLLEGE OF ENGINEERING ELECTRICAL ENGINEERING MODULE 2a...

BENGUET STATE UNIVERSITY COLLEGE OF ENGINEERING ELECTRICAL ENGINEERING MODULE 2a FUNDAMENTALS OF FREQUECNCY MODULATION I. FM CONCEPTS - In frequency modulation (FM), the carrier amplitude remains constant and the carrier frequency is changed by the modulating signal. As the amplitude of the information signal varies, the carrier frequency shifts proportionately. Frequency deviation, fd – the amount of change in carrier frequency produced by the modulating signal. Maximum frequency deviation occurs at the maximum amplitude of the modulating signal. a) Carrier; b) Modulating signal; c) FM signal; d) PM signal Problem 1: Frequency-Shift Keying (FSK) – When the modulating signal is a binary 1, the carrier frequency abruptly changes to a higher frequency level. The amount of the shift depends on the amplitude of the binary signal. This is widely used in the transmission of binary data in Bluetooth headsets, wireless speakers, and many forms of industrial wireless. II. PRINCIPLES OF PHASE MODULATION When the amount of phase shift of a constant-frequency carrier is varied in accordance with a modulating signal, the resulting output if phase modulation (PM). The maximum frequency deviation produced by a phase modulator occurs when the modulating signal is changing most quickly. For a sine wave modulating signal, that time is when the modulating wave changes from plus to minus or from minus to plus. Phase-Shift Keying (PSK) – the process of phase-modulating a carrier with binary data. Modulation index, mf – the ratio of the frequency deviation to the modulating frequency Problem 2: Property of and for the exclusive use of BSU. Reproduction, storing in a retrieval system, distributing, uploading and posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without prior written permission from BSU, is strictly prohibited.