US 6,788,745 B1 · Circuit and method for active termination of a transmission line

Abstract

An improved line driver and method for increasing the power efficiency, signal accuracy, and stability of a transmit signal on a transmission line are disclosed. The improved line driver uses a negative feedback control loop, thereby enhancing operational stability and suppressing both amplifier imperfections and discrete component manufacturing variances. Furthermore, when the improved line driver output stage is integrated with a hybrid, the composite circuit provides a power efficient full duplex solution for line driver applications. In a preferred embodiment, the improved line driver may comprise an active line termination control loop with current sense feedback, a first amplifier, and a second amplifier. The present invention can also be viewed as providing a method for increasing the stability, power efficiency, and accuracy of a line driver in a duplex transmission system. In its broadest terms, the method can be described as: applying a transmit signal to an input stage of a line driver; amplifying the transmit signal; using an active termination feedback control loop to generate a feedback signal; amplifying the feedback signal; combining the feedback signal with a duplex signal on a transmission line to generate a scaled transmit signal; and combining the scaled transmit signal with the duplex signal to recover a remotely generated receive signal from the transmission line.

Claims26

Dependent claims

A line driver with back-matching impedance emulation having a transmission line termination control loop, comprising:

a power amplifier having a power amplifier transmit gain configured with a first input for receiving a transmit signal, a second input for receiving an amplified feedback signal, and an output configured to provide an amplified transmit signal to the transmission line;
a current sensing means electrically coupled to the power amplifier output and configured to generate a feedback input signal;
a feedback amplifier having a negative transresistance forward transfer function configured to receive the feedback input signal and provide an amplified feedback signal to the second input of the power amplifier;
a first amplifier configured to receive the amplified feedback signal and apply a first amplifier transmit gain equivalent to the inverse of the power amplifier transmit gain to provide a first amplifier output signal;
and
a second amplifier configured to receive a first input comprising at least one signal from the transmission line and a second input comprising the first amplifier output signal, the second amplifier configured to mathematically combine the input signals to generate a scaled version of the transmit signal.

3 more elements

Dependencies are inferred from the claim text.

Circuit and method for active termination of a transmission line

Life of this patent

Circuit and method for active termination of a transmission line

Life of this patent

Abstract

Claims26