APPLICATION OF CONVENTIONAL TECHNIQUES 137 
which failed in method 4 but which succeeds here because of the sampling 
switch which separates the network from the plant. With pulsed net- 
works the designer can control both the poles and the zeros of the com- 
pensating network and ensure success of the design at the outset. These 
ideas are developed in some detail in Chap. 7. For the present purpose 
it will suffice to show later in this section that any realizable linear digital- 
controller pulse transfer function can be realized with a pulsed RC 
network. 


(l—e-@7) 
FN tec ia 
Cle ear 
Lag network ee when K= eee 
—e-@ 
Lead network 
(a) (b) 
Fic. 6.17. Block diagrams for typical pulsed-network transfer functions. 
The application of conventional techniques to the design of pulsed- 
network compensators requires the analysis of a few simple examples to 
give the designer a selection of tools for various requirements. Figure 
6.17 shows symbolically a few examples with their corresponding pulse 
Im[M2)] 

Re[Niz), 

0<a<l 

(a) (0) 
Fig. 6.18. Polar plots for typical pulsed-network transfer functions. 
transfer functions. The polar plots of the variations of these transfer 
functions as z moves around the upper half of the unit circle are shown in 
Fig. 6.18. It is clear from these diagrams that the configurations shown 
behave like lag and lead networks, respectively, and the application of 
these plots to polar-diagram design is obvious. Pulsed networks can also 
be used with pole-zero design methods using the root-locus method. 
