This chapter introduces a number of topics which should be useful for the succeeding chapters. Antenna gain, radiated power and transmission loss are commonly used terms when describing systems, but the precision given by the internationally agreed definitions of these terms is necessary if ambiguity is to be avoided. System performance is governed not only by the transmission loss, under some stated conditions, but also by the variability of the signal in time or space, which can then be described in statistical terms, and by the level of background signals either broadband noise or interfering transmissions. The statistical probability distributions in common use are introduced, and the benefits of diversity reception are outlined. The types of radio noise are described together with the ways in which noise power from a number of sources may be combined for use in performance prediction.
Basic principles 1, Page 1 of 2
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