Abstract: An improved analog front end and methods for increasing the power efficiency of duplex signals on a transmission line are disclosed. The improved analog front end bifurcates a hybrid into a fixed portion and an adaptive portion. The adaptive portion combines a biquad and a summer to produce a filter transfer function suited to compensate for transmission line irregularities. A method for configuring a local transceiver to minimize power requirements at a remote transmitter is disclosed. Broadly the method entails, applying a transmit signal to a front end in the absence of a remote signal; optimizing the transmit signal power; recording the reflected transmit signal; applying an adaptive filter in response to transmission line irregularities; and controllably adjusting the adaptive filter to minimize the amplitude of the reflected version of the transmit signal in the receive path. A method for recovering a remotely generated signal is also disclosed.

Abstract: A system and method for filter tuning are presented. The system comprises means for adjusting the components of a filter by coarse adjustments such that the filter is set with an initial cutoff frequency of adequate accuracy to satisfy the requirements of the filter application, and means for adjusting the components of the filter by fine adjustments such that the filter is set to maintain the accuracy of the initial cutoff frequency in response to cutoff frequency drift. The method comprises the steps of adjusting the components of a filter by coarse adjustments such that the filter is set with an initial cutoff frequency of adequate accuracy to satisfy the requirements of the filter application, and adjusting the components of the filter by fine adjustments such that the filter is set to maintain the accuracy of the initial cutoff frequency in response to cutoff frequency drift.

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 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.