(7.34)
The PN sequence is controlled by the state of the shift registers, the number of shift registers, and
the feedback connections. The latter two are described by the primitive polynomials. In Table 7.1, we
show some primitive polynomials.
To generate the PN sequence, the shift registers must be initialized or ???loaded??? with the first n
chips of the sequence, otherwise a shift or ???delay??? will be introduced into the output PN sequence.
This implies if one desires a certain shift in the PN sequence, then a proper initialization vector should
be loaded into the PN sequence generators shown in Figs. 7.22 and 7.23. Let??™s discuss time shifts in
more detail with a working example.
Consider the simple third-order (m3) case, with the primitive polynomial given as p(x)1xx3.
The Fibonacci-type generator is given in Fig. 7.24.
We wish to analyze the generated PN sequence by first discussing the state of the PN generator.
The state of the PN generator is defined by the contents of the shift registers. In Fig. 7.25, we show
the PN state as a function of time. The initial state of the PN generator is set to 100.
Note that shifts in sequences can be obtained and controlled by initial loading of the shift registers.
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