mod1 - All About Modulation Part I 1 Intuitive Guide to...

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All About Modulation – Part I 1 Intuitive Guide to Principles of Communications www.complextoreal.com All About Modulation Basic Concepts, Signal Space, Constellations and Phase Shift Keying modulations (PSK, QPSK, OQPSK, M-PSK, π /4-QPSK, MSK, and GMSK) Basic Concepts of modulation Three kinds of modulations Modulation is the process of facilitating the transfer of information over a medium. Sound transmission in air has limited range for the amount of power your lungs can generate. To extend the range your voice can reach, we need to transmit it through a medium other than air, such as a phone line or radio. The process of converting information (voice in this case) so that it can be successfully sent through a medium (wire or radio waves) is called modulation. We begin our discussion of digital modulation by starting with the three basic types of digital modulation techniques. These are; Amplitude-Shift Keying (ASK) Frequency-Shift Keying (FSK) Phase-Shift Keying (PSK) All of these techniques vary a parameter of a sinusoid to represent the information which we wish to send. A sinusoid has three different parameters than can be varied. These are its amplitude, phase and frequency. Modulation is a process of mapping such that it takes your voice (as an example of a signal) converts it into some aspect of a sine wave and then transmits the sine wave, leaving the actual voice behind. The sine wave on the other side is remapped back to a near copy of your sound. The medium is the thing through which the sine wave travels. So wire is a medium and so are air, water and space. The sine wave is called the carrier. The information to be sent, which can be voice or data is called the information signal. Once the carrier is mapped with the information to be sent, it is no longer a sine Copyright 2002 Charan Langton , revised Dec 2005 www.complextoreal.com
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