Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. C H A P T E R 5 ANGLE MODULATION AND DEMODULATION

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.1 Concept of instantaneous frequency.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.2 Phase and frequency modulation are equivalent and interchangeable.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.3 Generalized phase modulation by means of the filter H(s) and recovery of the message from the modulated phase through the inverse filter 1/H(s).

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.4 FM and PM waveforms.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.5 FM and PM waveforms.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.6 Estimation of FM wave bandwidth.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.7 (a) Variations of J n (β) as a function of n for various values of β. (b) Tone modulated FM wave spectrum.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.8 (a) Narrowband PM generator. (b) Narrowband FM signal generator.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.9 (a) Hard limiter and bandpass filter used to remove amplitude variations in FM wave. (b) Hard limiter input-output characteristic. (c) Hard limiter input and the corresponding output. (d) Hard limiter output as a function of θ.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.10 Block diagram of the Armstrong indirect FM transmitter.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.11 Designing an Armstrong indirect modulator.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.12 (a) FM demodulator frequency response. (b) Output of a differentiator to the input FM wave. (c) FM demodulation by direct differentiation.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.13 (a) RC high-pass filter. (b) Segment of positive slope in amplitude response

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.14 Effect of interference in PM, FM, and FM with preemphasis-deemphasis (PDE).

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.15 Preemphasis-deemphasis in an FM system.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.16 (a) Preemphasis filter and (b) its frequency response. (c) Deemphasis filter and (d) its frequency response.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.17 Superheterodyne receiver.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.18 (a) FM stereo transmitter. (b) Spectrum of a baseband stereo signal. (c) FM stereo receiver.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.19

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.19 FM and PM signals in the time and frequency domains.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.20 Signals at the demodulator: (a) after differentiator; (b) after rectifier.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure 5.21 FM modulation and demodulation: (a) original message; (b) recovered signal.

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure P.5.1-1

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure P.5.1-2

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure P.5.1-3

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure P.5.1-5

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure P.5.4-1

Modern Digital and Analog Communication Systems Lathi Copyright © 2009 by Oxford University Press, Inc. Figure P.5.4-2