DIGITAL MODULATION

We use the word modulation to mean the systematic alteration of one waveform, called the carrier, according to the characteristic of another waveform, the modulating signal or the message. In Continuous Wave (CW) modulation schemes, the carrier is a sinusoid. We use () c t and (), m t to denote the carrier and the message waveforms respectively. The three parameters of a sinusoidal carrier that can be varied are: amplitude, phase and frequency. A given modulation scheme can result in the variation of one or more of these parameters. Before we look into the details of various linear modulation schemes, let us understand the need for modulation.

2012

The concept of modulation is a key factor in commun ication, because without an appropriate modulation method or scheme, getting an expected th roug put in such a communication effort would be impossible to achieve. Communication engineers and researchers have not relented in trying to find the best modulation methods aimed at achieving an expected t hroughput, bandwidth/power efficiency, low error performance, etc in digital communication networks. Digital modulation is preferred to the analogue mo dulation due to their error-free capability.Moreso, this cho i e of digital modulation is dependent on the type of communication network that is to be established. Ho wever, trade-offs must be made between the bandwidt h efficiency, power efficiency and the cost of implem ntation of such a network. This paper focuses onsome methods usually employed in the process of modulation in digital communicati on networks. Specifically, binary phase shift keying, quadrature phase shift keying, eigh...

2004

Complex modulation may be achieved by imposing multiple modulation techniques on a single carrier, as in quadriture phase shift key amplitude modulation (QPSKAM) and the use of the FM carrier for both the FM modulation and the subsidiary communication authorization (SCA) modulation, or by using a succession of modulated carriers to modulate a higher level carrier, as in Bell System frequency domain multiplexing (FDM). Unintentional complex modulation is also frequently the result of poor filtering and unintended feedback loops.

Studying the process of analogue and digital modulation, 2017

The study of communication systems is largely based on signals and systems theory. An important objective in modulation is to produce a signal whose frequency range is suitable for transmission over the communication channel to be used. This paper presents an approach for studying the process of the main types of modulations of low and higher order. By using of computer simulations in MATLAB environment different types of modulation can be deep analyzed. It can be used for educational purposes in engineering education.

The purpose of a Communication System is to transport an information bearing signal from a source to a user destination via a communication channel.

Springer eBooks, 1992