iiiimbt*rof coluniiis We can tlmi esprws the addit ion of the outpiit signals by addition of tlir systcrn fiiiictioris Y ( )= H1(s)X(s) I H2(S)%(S) = [ (SJX(S) ill1 (6.41) This yields (6.42) - outpiit sigrials itlent ical Figure 6.18 shows a tcctlbnck sy m with ~riidtiple11iput5arid outputs Here tw take special e m - ' with thr dimeiisioris ot tlicl nnatiiws IYP begin vvith ncltlitictn t c;am(' 1~urnbc.r of rlrrnriit s I f input at tlie input All vectors here i m s t hav vcctor Xis) has A r olcnwnts tlien nintri s ) riirrst have AI colurnns aid inatrix G(s) niust h a v e Af iows At the output signal Y ( s )fioitr I h r outpiit of F(s) is c.oiiibinrd with the input of- G ( s ) , so i ) has K eleinerits, F(s)mist haw I< mist