Abstract: A search path recovery mechanism for a sequential decoder employs a prescribed self-concatenated “Loeliger” convolutional code, that is either decodable by the sequential decoder for data recovery, or is decodable (although sub-optimally) by a Viterbi decoder as an adjunct to the sequential decoder to improve statistics during path recovery. The Viterbi decoder is incorporated in an alternate decoder which includes metric calculators, that compute branch metrics, that are alternately coupled to the Viterbi decoder, operating at twice the symbol rate. Using estimate bits from the Viterbi decoder, a syndrome former estimates the recovered state and generates an estimate of the validity of the recovered state. Their validity is verified by a path recovery detector, which operates as a zero error detection filter by summing a prescribed number of previous syndrome former outputs.

Abstract: The method serves to add at least two values by means of a circuit. Both input values and output values are represented in differential form, either as a pair of voltages or as a pair of currents. The circuit consists of four transistors; it has a pair of current inputs for one of the input values, a pair of voltage inputs for the other input value, and a pair of current outputs for the output value. The voltage between the two voltage inputs corresponds to the first input value; the quotient of the currents through the two current inputs corresponds to the exponential of the other input value; and the quotient of the currents through the two current outputs corresponds to the exponential of the sum of the two input values. Values represented by voltages are easily transformed into current representation, and vice versa. The method is suitable for a variety of applications and the circuit can be cascaded both with copies of itself and with other circuits.

Abstract: A search path recovery mechanism for a sequential decoder employs a prescribed self-concatenated “Loeliger” convolutional code, that is either decodable by the sequential decoder for data recovery, or is decodable (although sub-optimally) by a Viterbi decoder as an adjunct to the sequential decoder to improve statistics during path recovery. The Viterbi decoder is incorporated in an alternate decoder which includes metric calculators, that compute branch metrics, that are alternately coupled to the Viterbi decoder, operating at twice the symbol rate. Using estimate bits from the Viterbi decoder, a syndrome former estimates the recovered state and generates an estimate of the validity of the recovered state. Their validity is verified by a path recovery detector, which operates as a zero error detection filter by summing a prescribed number of previous syndrome former outputs.

Abstract: A circuit module for data processing comprises several first inputs (Ix,i), several second inputs (Iy,i) and several outputs (Ii,j). First transistors (Ti,j) combine the first and second inputs. Each of the first transistors (Ti,j) is connected at its emitter or source with a first input and at its base or gate with a second input. Each second input is further connected to the base or gate and the emittor or source of a second transistor (Ti). The currents of the outputs correspond to the product of the currents through the individual inputs. By combining the outputs sum products can be calculated, especially for computing discrete probability distributions. The combination of several circuit modules allows to solve complex signal processing tasks.