An opto-electronic Viterbi traceback processor for decoding convolutional codes

The design, circuits, and layout of the Viterbi traceback processor (VTP), a full-custom ASIC utilizing optical, analog, and digital circuits, are presented, The VTP subsystem, when combined with a holographic (optical) metric generation subsystem, is designed to implement the Viterbi decoding algorithm. The prototype chip, 6900×6800 μm² was designed to decode convolutionally encoded data from a rate=1/2, K=5 encoder and is comprised of 2^k photoreceptors, 2^k-1 comparators, a 2^K-1×16 array of 2-input multiplexor/shift register cells, and two sizes of clock buffer/driver circuits. Two scan-path chains have been designed in for testability