Receiver Characteristics and their Measurement
III.1 Objectives and Benefits
Antennas provide very different signal scenarios for receivers. Besides the strong and sometimes very weak useful signals, many other signals are fed to the receiver input. One of the main tasks for the radio receiver is to select the signal of interest and demodulate it in optimum quality to retrieve the information content. This process should be affected as little as possible by the other signals present, the interfering signals. Technical parameters are used to describe how a receiver performs in different situations. These so-called receiver characteristics, receiver properties or receiver parameters define the equipment efficiency and allow comprehensive objective comparisons. When comparing data from different sources, it is important that these parameters have been determined under the same conditions! Only this gives a meaningful and transparent comparison. While some specifications like receiver sensitivity (Section III.4) can be converted if established with different receive bandwidths (Section III.6), the comparison of other parameters is utterly useless if these are not measured by identical methods. By dividing the following text into two parts, the first of which describes the basic meaning of a receiver parameter and the other details of the measuring procedure required, the book will help to develop a feeling for the true significance of the specified characteristics.