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3.3. OBFN simulator Implementation
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number of rings in a path is known. Counting the non-empty positions in a column
results in having the number of times a delay element is shared between paths. As a
concrete example, take a look at Table 3.2.
Table 3.2: Connection matrix 8x1 OBFN
DE1 DE2 DE3 DE4 DE5 DE6
Input
Input
Input
Input
Input
Input
Input
Input
3.3.2
1
2
3
4
5
6
7
8
1
-
2
2
-
1
-
4
4
4
4
1
-
2
2
DE7
1
Delay distribution within the OBFN
For the simulation, a path instance is created containing multiple delay element instances. The creation of the delay element instances is done according to the value on
position i, j in the connection matrix, where the ith row is the representation of the
path, and the value of position i, j the length of the delay element. The parameters
for each delay element are obtained using the same methods as described in Chapter
2. The input signal is fed through all the newly created instances, where the results
are added. When examining the connection matrix, multiple non-empty values in a
column indicate a shared delay element among different paths. For example, DE4 is
being used by four paths. The delay of the fifth path solely depends on DE4 , which
means that the value of DE4 becomes a constant when the target delay for the fifth
path is known. The required ∆τ delay difference between the fifth and sixth path
thus have to be realized by just one ring. To calculate the distribution of delays while
keeping the shared paths in mind, an overflow algorithm is created. The code is given
in listing 3.2.
We made use of the fixed structure of the binary tree structure and the DFS algorithm to create the connection matrix. One of the useful properties of the connection
matrix when using this approach is that the number of rings in each row of the matrix
is decreasing from left to right, from which we can benefit now. Note that this also
means that when using other kinds of topologies, the overflow algorithm might need
some adjustments.