Digital Modulation and Transmission Principles of Communication Systems, Third Edition Herbert Taub, Donald L Schilling, Goutam Saha Chapter 6 : Part A Digital Modulation and Transmission PROPRIETARY MATERIAL. © 2008 The McGraw-Hill Companies, Inc. All rights reserved. No part of this PowerPoint slide may be displayed, reproduced or distributed in any form or by any means, without the prior written permission of the publisher, or used beyond the limited distribution to teachers and educators permitted by McGraw-Hill for their individual course preparation. If you are a student using this PowerPoint slide, you are using it without permission.

Binary Phase Shift Keying (BPSK) Sinusoidal carrier changes phase depending on binary signal level of digital data. If message signal b(t) is either +1 V or -1 V

BPSK reception Received signal has the form Squaring, BP Filtering above after frequency divider generates carrier. Multiplying carrier with received signal The integrator and dump (bit-synchronized) of above gives

BPSK Block Diagram

BPSK Spectrum

BPSK : Geometric Representation BPSK signal can be represented in terms of one orthonormal signal Distance between the signal, d is inversely proportional to the probability of error in presence of noise.

Quadrature Phase Shift Keying (QPSK)-1

QPSK-2

QPSK-3 The QPSK system discussed is called offset or staggered QPSK abbreviated OQPSK. Phase change only by 900. In non-offset QPSK there is an additional D-FF in one line of Fig. 6.10, thus even-odd could be same time, phase change could be 1800.

Symbol vs. Bit Transmision In BPSK, each bit of duration Tb is individually treated. In QPSK, two bits are lumped together to form what is termed a symbol. The symbol can have any of the four possible values corresponding to the two-bit sequences 00, 01, 10 and 11. At the receiver, each signal represents one symbol and correspondingly, two bits. When bits are transmitted, as in BPSK, the signal changes occur at the bit rate. When symbols are transmitted, the changes occur at the symbol rate which is one-half the bit rate. Thus, symbol time is Ts =2Tb

QPSK Receiver

QPSK : Geometric Representation

M-ary Phase Shift Keying-1

M-ary Phase Shift Keying-2 Bandwidth,

M-ary PSK Transmitter

M-ary PSK Receiver

Binary Frequency Shift Keying (BFSK)

BFSK Spectrum

BFSK Receiver

BFSK : Geometric Representation

Non-Orthogonal BFSK When two FSK signals are not orthogonal Gram-Schmidt procedure can be used for geometric representation

M-ary FSK

M-ary Communication System

End of Part A Chapter 6