Noise in Electronic Communications Systems - 1312 Words

An additive noise is characteristic of almost all communication systems. This additive noise typically arises from thermal noise generated by random motion of electrons in the conductors comprising the receiver. In a communication system the thermal noise having the greatest effect on system performance is generated at and before the first stage of amplification. This point in a communication system is where the desired signal takes the lowest power level and consequently the thermal noise has the greatest impact on the performance. This characteristic is discussed in more detail in Chapter 10. This chapter’s goal is to introduce the mathematical techniques used by communication system engineers to characterize and predict the†¦show more content†¦It turns out that W(t) is accurately characterized as a stationary, Gaussian, and white random process. Consequently, our first task is to define a random process (Section 9.1). The exposition of the characteristics of a Gaussian random process (Section 9.2) and a stationary Gaussian random process (Section 9.3) then will follow. A brief discussion of the characteristics of thermal noise is then followed by an analysis of stationary random processes From this point forward in the text the experimental outcome index will be dropped and random processes will be represented as N(t). EXAMPLE 9.1 A particular random process is defined as N(t) = U exp[−|t|] + V (9.1) where U and V are independent random variables. It is clear that with each sample value of the random variables U(ω) and V (ω) there will be a time function N(t, ω). This example of a random process is not typical of a noise process produced in real communication systems but it is an example process that proves insightful as we develop tools to characterize noise in communications. EXAMPLE 9.2 A noise generator and a lowpass filter are implemented in Matlab with a sample rate of 22,050 kHz. Recall each time Matlab is run this is equivalent to a different experiment outcome, i.e., a different ω. A sample path of the input noise to the filter, W(t), and a sample path at the output of the filter, N(t), is shown in Figure 9.3 for a filter with a bandwidth of 2.5 kHz. It isShow MoreRelatedWireless Communication : A First Decade Of The 20th Century1356 Words   |  6 PagesTelecommunication occurs when the exchange of information between two or more entities (communication) includes the use of technology. Communication technology uses channels to transmit information (as electrical signals), either over a physical medium (such as signal cables), or in the form of electromagnetic waves.[1][2][3][4][5][6] The word is often used in its plural form, telecommunications, because it involves many different technologies. Early means of communicating over a distance includedRead MoreUnit 1 Assignment 1 Essay example973 Words   |  4 PagesSection 1-1 1. Define modulation. 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