US 10,256,921 B2 · Reducing impedance discontinuities on a shared medium

Abstract

Systems and methods are provided for reducing the effects of an impedance mismatch between a communications system and a shared communications medium. A communication system, such as a transceiver within a cable modem, switches between various operating modes including a transmit mode, a receive mode, and a standby mode. The standby mode may be used while the transceiver is in an idle state between modes, such as while changing an amplifier gain states in between transmissions. While transitioning between modes, the impedance presented by the communications system can temporarily fluctuate causing unwanted signal reflections to propagate out of the communications system and on to the shared medium. Circuitry within the communications system, such as transmission circuitry including an adjustable attenuator, may be placed into a hybrid attenuation-isolation mode during the transition causing the magnitude of any unwanted signal reflections to be attenuated and reducing the impact on the shared medium.

Claims23

Dependent claims

A method for reducing impedance changes and signal reflections in a communications system, the method comprising:

connecting an output to a load path presenting a first output impedance configured to match an impedance of a shared communications medium, the output configured to be coupled to the shared communications medium;
enabling a transmission amplifier within a transmission path of the communications system;
determining whether the transmission amplifier is operatively configured to provide a transmission signal;
disconnecting the output from the load path;
and
connecting the output to the transmission path responsive to a determination that the transmission amplifier is operatively configured to provide the transmission signal, the transmission path configured to present a second output impedance matching the impedance of the shared communications medium.

3 more elements

A transceiver system having an output configured to match an impedance of a shared communications medium, comprising:

a transmission amplifier configured to be coupled to the output and provide a transmission signal to the output in a first mode of operation, the transmission amplifier being configured to present a first output impedance substantially matching the impedance of the shared communications medium;
a load path configured to be coupled to the output in a second mode of operation and present a second output impedance substantially matching the impedance of the shared communications medium;
receiving circuitry configured to be coupled to the output and receive a reception signal from the output in a third mode of operation, the receiving path being configured to present a third output impedance substantially matching the impedance of the shared communications medium;
switching circuitry configured to selectively couple one of the transmission amplifier, the receiving circuitry, and the load path to the output;
and
a controller configured to receive an indication that the transmitter system is to transition among the first, second, and third modes of operation, and in response to receiving the indication, to control the switching circuitry to decouple the transmission amplifier from the output and couple the load path to the output, to decouple the load path from the output and couple the transmission amplifier to the output, to decouple the receiving circuitry from the output and couple the load path to the output, or to decouple the load path from the output and couple the receiving circuitry to the output.

3 more elements

Dependencies are inferred from the claim text.

Reducing impedance discontinuities on a shared medium

Life of this patent

Reducing impedance discontinuities on a shared medium

Life of this patent

Abstract

Claims23