DPLL based hardware SOM with a new winner-take-all circuit

The self-organizing map (SOM) has found applicability in a wide range of areas. This paper proposes a new winner-take-all method for hardware SOM with phase-modulated pulse signal. The system uses phase of square waveform to hold the value of each input vector element. The system uses digital phase-locked loop (DPLL) as a computing element because the operation of the DPLL is very similar to that of SOM´s computation. The proposed winner search method is realized by taking advantage of the nature of phase modulated signal, and neighborhood function is also implemented with simple hardware. In addition, the winner search requires no global communication, which makes the architecture scalable. The proposed SOM architecture is described in VHDL and its feasibility is verified by simulation. Preliminary simulation results show that the proposed SOM has good clustering capability with the topology preserving nature.