ABSTRACT
If we are to be true to the word "general" in the chapter title, we must restrict ourselves to constant-coefficient linear models; a general mathematical theory that is practically useful exists only for this class of system descriptions. Most of the chapter is devoted to this limited but important area. However, as has been demonstrated in all the earlier chapters, we don't want to limit our design perspective so severely; it rules out many nonlinear designs which are superior to the linear. Simulation software will usually be the main tool in these situations, but familiarity with linear theory often provides approximate insights which can be helpful in the initial stages of design, even if the final model is strongly nonlinear. Chapter 9 will thus include some nonlinear system examples, even though a general theory of such systems is largely lacking.
