ABSTRACT
Many of the chapters in this book consider how we can accurately measure the shape or amplitude of signal patterns. In practice, we often also need to perlorm time or frequency measurements. These measurements can be performed in a variety of ways. However, before looking at some examples it is worth asking, just what do we mean by the 'frequency' of an input signal? The reason for this question is that, surprisingly, there is more than one definition of the term 'frequency' and we may get different results from a measurement depending upon which one the chosen technique assumes. There are three related problems which arise when we want to defme and measure the frequency of a waveform. To understand these we can start by considering figure 24.1. This shows three signal pattern observations, each made over a finite duration, T 0 .
