Analog & Digital Modulation Techniques : an Overview

A tremendous technological transformation during the last two decades has provided a potential growth in the area of digital communication and lot of newer applications and technologies are coming up everyday due to these reasons. Restricting overself to the domain of modulation techniques a brief overview over different analog and digital modulation techniques has been provided in this article through extensive literature survey in a tabular manner enabling to analyze and establish the superiority at a glance of a specific modulation technique for a particular application. 1.0 INTRODUCTION: Living in the era of communication every thing may be video, audio or any information in the form of electrical signal is termed as data and there is an enormous requirement of data transfer between two or more point through the world wide web, every moment of the clock, which is a big threaten to the existing communication systems because of the problems like spectral congestion, severe adjacent & co-channel interference problems and noise corrupted data reception etc. This has resulted in serious need for the research work all around the world for the development of the communication systems which can handle the above said problems, where each aspect of the communication systems is dealt with the development of new encoding techniques, modulation techniques, possibilities for newer transmission channels and off course the demodulation and decoding techniques [1, 2]. The design of a communication system is application oriented and is dependent on the type of the signal. The choice of digital communication technique over its analog counter part becomes more evident of the fact that it provide larger immunity to noise for even at the price of large bandwidth requirements, where as the requirement of video, Audio and data over the computer network or the mobile telephony network termed as the third generation (3G) mobile communication poses a serious problem for the bandwidth so The existing modulation techniques need to be modified for the purpose where it can handle both the situations of noise and bandwidth efficiency [3, 4]. The major advantage of using digital modulation technique is that the use of digital signals reduces hardware, noise and interference problems as compared to the analogue signal where large number of waveforms will be required resulting in a larger bandwidth for the symbol to be transmitted [5]. Over the past years various modulation techniques have been designed and extensively used for various applications but the modern communication system requires data transmission at a higher rate, larger bandwidth in order to have multimedia transmission, hence the existing modulation techniques are not able to provide a complete solution keeping this in the view the authors of this article have tried to draw a sketch within the existing modulation techniques to derive out exactly what modifications or the alterations in the present techniques may sort out the problem or there is still a need for designing a new modulation technique for the purpose of the present communication system requirements [6, 7]. 2.0 Classification of Modulation Techniques. Modulation is the process of varying some parameter of a periodic waveform in order to use that signal to convey a message. Normally a high-frequency sinusoidal waveform is used as carrier signal. For this purpose ,if the variation in the parameter of the carrier is continuous in accordance to the input analog signal the modulation technique is termed as analog modulation scheme if the variation is discrete then it is termed as Digital Modulation Technique [8]. Table-1: Type of Modulation Techniques Sr. No . Modulation Techniques Type Notation 01 Analog Modulation Techniques (i) Amplitude Modulation (ii) Frequency Modulation (iii) Phase Modulation A.M.