## Signal Flow Graph

One possible*signal flow graph*(or

*system diagram*) for Eq.(5.1) is given in Fig.5.1a for the case of and . Hopefully, it is easy to see how this diagram represents the difference equation (a box labeled ``'' denotes a one-sample delay in time). The diagram remains true if it is converted to the

*frequency domain*by replacing all time-domain signals by their respective

*z*transforms (or Fourier transforms); that is, we may replace by and by . transforms and their usage will be discussed in Chapter 6.

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Difference Equation