The Logical Design of a Digital Pseudorandom Noise Generator

A digital pseudorandom noise generator is described and analyzed. The generator output is predictable and deterministic in nature allowing precise calibration of the signal bandwidth occupancy. It is designed by use of a linear feedback shift register and exclusive-or (modulo-two) logic elements to produce maximum cycle sequences of 2N-1 where N is switch selectable. Modulo-two arithmetic and delay operators describe the generator by use of characteristic polynomials. Many independent noise sources are derived since there is a complete lack of correlation between outputs delayed a shift command apart. The auto-correlation function of the binary signal determines the time functions suitability as a random noise source. By use of this function the corresponding spectral density function is shown to approximate (sin x/x)2. By use of this function the bandwidth of the generator is shown to be directly proportional to the shift oscillator frequency. Two examples are given illustrating the use of the generator.