A very high speed Viterbi decoder with a circularly connected 2-dimensional analog CNN cell array is disclosed. The circuit is circularly connected, forming a cylindrical shape so that the cells of the last stage are connected to those of the first stage. Such configuration enables the conceptually infinitive length of the trellis diagram to be implemented with a limited size of circuits. Use of the analog circuits does not require the necessity of the A/D converters. With the parallel analog processing structure, its decoding speed becomes very high. Features of the proposed Viterbi detector are compared with those of the conventional digital Viterbi decoder.