To interconnect three or more adaptors in a wave digital filter, it is now typical to use a Binary Connection Tree (BCT) [152,364], in which only three-port adapters are needed. Three-port adaptors can handle any combination of parallel and series connections.
For example, suppose we wish two connect adaptors
and
in
parallel using a new three-port parallel adaptor
, as shown in
Fig.F.6. Adaptors
and
are normally themselves three-port
adaptors in a BCT, but they can be any kind of adaptor (scattering
junction). All that matters from the point of view of adaptor
is
the connecting port wave impedances
and
. Then to make the
top port of adaptor
reflection free, we choose its wave
impedance
to be the parallel combination of all other
connected adaptors, i.e.,
in this case.
We mark the top outgoing port of
as being reflection-free using
the `
' symbol.
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