Graphics Programs Reference
In-Depth Information
Figure 4.18c. Contour plot corresponding to Fig. 4.18a.
4.4.3. Pseudo-Random Number (PRN) Codes
Pseudo-Random Number (PRN) codes are also known as Maximal Length
Sequences (MLS) codes. These codes are called pseudo-random because the
statistics associated with their occurrence are similar to that associated with the
coin-toss sequences. Maximum length sequences are periodic. The MLS codes
have the following distinctive properties:
The number of ones per period is one more than the number of minus-ones.
1.
Half the runs (consecutive states of the same kind) are of length one and
one fourth are of length two.
2.
Every maximal length sequence has the Ðshift and addÑ property. This
means that, if a maximal length sequence is added (modulo 2) to a shifted
version of itself, then the resulting sequence is a shifted version of the orig-
inal sequence.
3.
Every n -tuple of the code appears once and only once in one period of the
sequence.
4.
The correlation function is periodic and is given by
5.
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