Compact Layouts of Banyan/FFT Networks

A two-layer pattern is presented for the crossover pattern that appears as the FFT signal flow graph and in many switching networks like the banyan, delta, or omega nets. It is characterized by constant path length and a regular pattern, providing uniform propagation delay and capacitance, and ameliorating design problems for VLSI implementation. These are important issues since path length grows linearly with the number of inputs to such networks, even though switching delay seems to grow only logarithmically.