Nortel Networks Corporation

Gordon B Neilson

David M Tholl

Martin O'Flaherty

Charles E Norman

Trevor A Page

Roman Nemish

A communication system uses a reflected signal to determine the location of an impedance mismatch along a transmission path. The system provides a forward signal through the transmission path, and obtains, using a feedback loop, forward signal samples and reflected signal samples from the forward signal and a reflected signal, respectively. Assuming a significant mismatch exists, the system identifies a time delay of any impedance mismatch from the forward signal samples and the reflected signal samples. The physical location of the mismatch along the transmission path is determined based on the time delay and a propagation velocity of the forward signal through the transmission path. The magnitude of the mismatch is determined based on a voltage gain calculation, a loss profile of the transmission path, the propagation velocity, and the time delay. In one embodiment, the method is carried out in a communications base station that includes an amplifier, a feedback loop, a feedback receiver, and a processor.

Method and apparatus for locating impedance mismatches in a radio frequency communication system

A significant part of the cost of a base station in the cellular mobile radio system is the power amplifier. Thus it is desirable to maximise usage of a power amplifier and in particular to gain the best power output from the amplifier or to improve its efficiency. Such power amplifiers, however, must operate within strict spectral boundaries and thus power amplifiers are typically over-specified in order to ensure that the spectral requirements are met. By measuring the output of the amplifier and determining distortion factors and then adaptively adjusting the operating characteristics of the amplifier, the degree of over-specification of the amplifier required may be reduced with consequent cost and environmental savings.

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Calgary, Canada

Gordon B Neilson