10 ENGINEERIN G BACKGROUN D There ar e junctions whic h ad d signal s an d junctions whic h subtrac t them . U+V V The basi c feedbac k syste m i s T U V V He!— which i s instructive t o analyze . Th e diagra m i s equivalent t o th e equations : 6 = PCe, e = i- BO. Combine the m t o ge t 9 = PCi - PC BO. Consequently , (/ + PCB)6 = PCi. Then 6 = (I + PCB)~ l PCi an d s o the transfe r functio n fo r th e syste m i s (1.6)4 {I + PCB)~ l PC. 4 This can be written in at least three other forms, with different dimension s of the inverse in nonsquare cases, by doing algebra in a different order . I t involve s [/ + PCB\~ l , [ 1 + BPC}" 1 , and [I + CBP}- 1 .
Previous Page Next Page