Shift-register generators , random

An alternative method for excitation of nuclei over a range of chemical shifts is by irradiation with a weak, noise-modulated radio-frequency, instead of with strong r.f. pulses. In one realization of this method, protons were irradiated with repetitive sequences of noise that was truly random,162 and, in another,163 fluorine nuclei were excited by pseudo-random noise generated by amplitude modulation of the r.f. with maximum-length sequences of pulses from a computer or shift register (a series of flip-flop devices connected by feedback loops). With the carrier wave suppressed, the latter process is equivalent to phase modulation of the r.f. by+7r/2 radians when the pulse is turned on, and by —ir/2 radians when it is turned off. This method is identical with that used in most broadband, heteronuclear, noise decouplers, except that greater power is required for decoupling. 

F. Schmid and N. B. Wilding, Errors in Monte Carlo Simulations Using Shift Register Random Number Generators, Int. J. Mod. Phys. C 6(6), 781-787 (1995). 

Linear feedback shift raster (LFSR) A method of construction of a register with feedback to generate pseudo random numbers. 

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