[Xy-pic] Diagrams of digital LTI filter

[Nicolas Ratier]

With the precious help of Richard Lewis, I drawn the "Direct Form" of a FIR.
I send the result with the hope it will be useful for other EE scientist.
<keyword> : xypic xy-pic xygraph FIR DSP digital signal processing
(for "google" search)

Nicolas

==============================================================================
\xygraph{
!~*{=}
!~-{@{-}|<>(.6){\object@{>}}}
% The {\bullet} groups represent nodes
{\bullet}="start"-[r] {\bullet} (? -^{z^{-1}} [r]{\bullet},
                                    -^{h_0}    [d]{\bullet} -[r]{\bullet})
                   [r] {\bullet} (? -^{z^{-1}} [r]{\bullet} 
-^{h_2}[d]{\bullet},
                                    -^{h_1}    [d]{\bullet} -[r]{\bullet})
                   [r] {\bullet} (? -@{--}     [r]{\bullet})
                   [d] {\bullet} (? -@{--}     [r]{\bullet})
                   [ur]{\bullet} (? -^{z^{-1}} [r]{\bullet} 
-^{h_N}[d]{\bullet},
                                    -^{h_{N-1}}[d]{\bullet} -[r]{\bullet})
                   [dr]{\bullet} (? -[r]{\bullet}="end")
% Here we add `x_n' before the "start" node
"start"!{"start"+L*+!R{x_n}}
% Here we add `y_n' to right of the "end" node
"end"!  {"end"  +R*+!L{y_n}}
}
==============================================================================