Hybrid Decoding of Bipolar Signals

An analog-digital hybrid decoder which combines amplitude and duration threshold detection and bipolar violation sensing capabilities for decoding bipolar signals is described. The main features of the decoder are: 1) a preamplifier with automatic gain control (AGC), 2) amplitude and duration threshold detectors, 3) a bipolar violation sensor, and 4) a unipolar pulse generator. The decoder is extremely robust and is self-synchronizing. If, during operation, burst errors occur, introducing bipolar violations in the received signal, the decoder decides that, where a violation has occurred, a binary "0" was transmitted. If, for some reason, the decoder is perturbed from its synchronous condition, it requires at most 1-b duration to reacquire synchronization. That is, the decoded message contains at most one erroneous bit.