Method and apparatus for hybrid ring generator design

摘要

A method and apparatus for generating a pseudorandom sequence using a hybrid ring generator with low hardware cost. When a primitive polynomial over GF(2) is selected as the characteristic polynomial f(x) to construct a hybrid ring generator, the circuit implementing f(x) will generate a maximum-length sequence (m-sequence). The hybrid ring generator offers unmatched benefits over existing linear feedback shift register (LFSR) based maximum-length sequence generators (MLSGs). Assume k 2-input XOR gates are required in a standard or modular LFSR design. These benefits include requiring only (k+1)/2 2-input XOR gates, having at most one level of a 2-input XOR gate between any pair of flip-flops, enabling the output of each flip-flop to drive at most 2 fanout nodes, and creating a highly regular structure that makes the new design more layout and timing friendly.

主权项

1. An apparatus using an n-stage hybrid ring generator to generate a pseudorandom sequence, the hybrid ring generator implementing a characteristic polynomial f(x) of degree n over GF(2) that contains k+2 terms, where 0 (a) n flip-flops connected to each other in a given order to form a ring structure with at least one said flip-flop placed on a top row and the rest of said n flip-flops placed on a bottom row; and (b) (k+1)/2 2-input XOR gates each placed between a select pair of said n flip-flops such that at least one said XOR gate is connected on said top row, wherein said hybrid ring generator has at most one level of XOR logic between every pair of said n flip-flops and each said flip-flop output in said hybrid ring generator drives no more than 2 fanout nodes.