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APPENDIX E Frequency response analysis of linear systems 295
1.0
DENOTES HARMONIC FREQUENCY
BASIS – SAME TOTAL DURATION
0.5 FOR ALL SIGNALS
0.2
ENERGY/[T X (PULSE AMPLITUDE) 2 ] 0.05 63 –BIT
0.1
0.02
0.01
7 –BIT 31 –BIT
0.005
0.002
0.001
1 10 100
Harmonic
FIG. E.11
Frequency spectra for several PRBS signals [4].
A shift register operates by moving the contents of each register (0 or 1) to the
next register to the right at each shift. This operation empties the left-most register.
Feedback involves moving the sum (modulo two) of contents to the left-most regis-
ter. For example, consider a three-register arrangement with adder feedback from
registers 1 and 3. The initial contents of the registers are all set equal to 1 in this
example. Operation of the system results in the following:
