signals - Fundamental of Signals We are surrounded by...

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Chapter One Fundamentals of Signals Page 1 www.complextoreal.com Fundamental of Signals We are surrounded by man-made and natural signals. In general when we talk about communications, we are talking about transfer of desired information whether right up close or to far destinations using signals of some sort. Communications via electronic means consists of generation of signals that contain or carry intelligent information and its processing at the receiver to extract the intelligent information. In general a signal is a description or relationship of one parameter to another, such as the relationship of voltage with time for communications signals. This relationship can be discrete or continuous. The type of signal, analog or discrete, used for communication depends on how far the signal has to travel and the medium it will have to pass through. On the receiving site, this signal is decoded and the intelligent information recovered. There are various distinct steps both in the generation, transfer and the receiving of these signals, most specific to either analog or discrete signal processing. The tools for doing this processing whether discrete or analog are governed by communications theory. Unit Link Network Fig. - 1.1 Study of communications can be conceptualized under unit, link and network level. In general the field of communications can be conceptualized in three fields of study. There is the component or the physical unit. Here the analysis consists of performance issues of individual units within the chain. We may worry about the performance of the component such as a filter under ideal or specified conditions. Example in case of a cell phone would be design of the handset which alternately is the design of the amplifier, antenna, filters and baseband signal processing algorithms. Then comes a single link between a sender and a receiver. This involves looking at how the signal would go from the handset to the base station and to the intended recipient and vice versa. These are waveform or the signal issues. How is the signal affected going from one unit to the next. We study modulation, channel effects, power required etc. as in Fig. (1.2). The third main part is the integration of various communications link to make a network. A cell network has many base stations, many users, how do we design a network so each is uniquely identified and does not interfere and the network capacity is not compromised? These are network issues and we study issues of network design, congestion issues and access control. Generation of information Conversion to signals for transmission (Coding, Modulation) Medium through which signals travel (wire, air, space) Receiving and processing of signal (Demodulation and Decoding) Convert back to orginal form of information Fig. 1.2 Generation of signals in a communications link Signal types Most signals in nature are analog. Examples of these are sound, noise, light, heat, and electronic communication signals going through air (or space). These signals vary continuously and the processing for
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