ELECTRONIC COMMUNICATIONS A SYSTEMS APPROACH CHAPTER Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Electronic Communications: A Systems Approach Beasley | Hymer | Miller Fundamental Communications Concepts 1

Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Introduction Communications Systems and Modulation  Function of any communication system is to transfer information from one point to another.  All systems consist of three elements: Transmitter Receiver Channel

Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Figure 1-2 Communication system block diagram.

Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Introduction Communications Systems and Modulation  Modulation Impressing low-frequency voltages (information) onto high-frequency signal (carrier) for transmission.  Demodulation or detection Recovering (separating) information from the high frequency carrier.

Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Introduction Communications Systems and Modulation  Carriers often sine waves; amplitude, frequency, and phase are the only characteristics of a sine-wave carrier that can be modified.

Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Figure 1-1 Sine wave represented as a rotating phasor.

Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Table 1-1 Radio-Frequency Spectrum

Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Introduction The Electromagnetic Spectrum  Magnetic fields surround moving electric charges (currents).  Electric and magnetic fields both result from voltage potentials and current flows.  Electromagnetic energy Electric and magnetic fields form at right angles to each other and at right angles to direction of travel.

Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Introduction The Electromagnetic Spectrum  Magnitudes of both electric and magnetic fields are constant.  Transducer Converts energy  Electromagnetic spectrum Entire range of signals occupying all frequencies

Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Introduction The Electromagnetic Spectrum  Audio frequencies Can be heard by human ear  Radio frequencies Above 50 kHz  Transmission of signals Wireless/physical media

Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved  Characteristics Broad range of frequencies, Referred to in terms of wavelength instead or of Hertz (aka, cycles per second) Depends upon the part of the spectrum and traditional references Electromagnetic Spectrum

Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved  Characteristics Another view by Carl Rod Nave of Georgia State University Converting from frequency to wavelengths Speed of light = Frequency of the waveform * wavelength Electromagnetic Spectrum Note: the speed of light in a material depends upon the electrical and magnetic characteristics of the material

Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Introduction The Electromagnetic Spectrum  Communications systems limited by two factors: Bandwidth Noise