Friday, 16 May 2014

PN (Pseudo-Noise) sequences

PN sequence is a noise-like spreading code which is basic to the operation of spread-spectrum modulation. A PN sequence is defined as a coded sequence of 1's and 0's with certain auto-correlation properties. PN sequence is periodic i.e., a sequence of 1's and 0's repeats itself exactly with a known period.
     The 'maximum-length sequence' represents a commonly used periodic PN sequence. Such sequences have long periods and require simple instrumentation in the form of a linear feedback shift register.
Maximum-length sequence generator for m=3 is shown in the figure below.                                                

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