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POWER AMPLIFIER BIAS ADJUSTMENT IN FIELD FOR HFC NODE AND AMPLIFIER

IP.com Disclosure Number: IPCOM000244896D
Publication Date: 2016-Jan-27
Document File: 4 page(s) / 64K

Publishing Venue

The IP.com Prior Art Database

Related People

Maxwell Huang: AUTHOR

Abstract

A Bias Adjustment in Field (BAiF) mechanism is intended to incorporate in nodes and amplifiers used in the Hybrid Fiber Coaxial (HFC) network. This mechanism could be used for reducing the power in several scenarios, such as:

• When the actual RF output power (the combination effect of output level and Quadrature Amplitude Modulation (QAM) channel count) is lower than a maximum RF output power of Power Amplifier (PA) specified; • The End-of-Line (EOL) Modulation Error Ration (MER) performance is more than good enough to support the application, leaving room to reduce the power by a trade-off in performance. • The temperature inside a housing (or active device like power amplifier if is designed to have such measuring ability) is sensed to be too hot to ensure the reliability.

This cost-effective mechanism could have the significant impact on power savings when it is tied to those intelligent features to be implemented in new HFC products and system, like the spectrum capture and the Adaptive Power System Interface Specifications (APSIS).

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POWER AMPLIFIER BIAS ADJUSTMENT IN FIELD FOR HFC NODE AND AMPLIFIER

AUTHOR:

Maxwell Huang

CISCO SYSTEMS, INC.

ABSTRACT

    A Bias Adjustment in Field (BAiF) mechanism is intended to incorporate in nodes and amplifiers used in the Hybrid Fiber Coaxial (HFC) network. This mechanism could be used for reducing the power in several scenarios, such as:

• When the actual RF output power (the combination effect of output level and Quadrature Amplitude Modulation (QAM) channel count) is lower than a maximum RF output power of Power Amplifier (PA) specified;

• The End-of-Line (EOL) Modulation Error Ration (MER) performance is more than good enough to support the application, leaving room to reduce the power by a trade-off in performance.

• The temperature inside a housing (or active device like power amplifier if is designed to have such measuring ability) is sensed to be too hot to ensure the reliability.

    This cost-effective mechanism could have the significant impact on power savings when it is tied to those intelligent features to be implemented in new HFC products and system, like the spectrum capture and the Adaptive Power System Interface Specifications (APSIS).

DETAILED DESCRIPTION

     Power Amplifiers (PAs) are usually designed by device vendors with a bias current adjustment feature to allow product developers to set the bias current to an optimal performance associated with the target radio frequency (RF) output power. But

Copyright 2016 Cisco Systems, Inc.
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for the products shipped to-date, it has been always fixed to the maximum current to enable the maximum output capability of the PA.

    In a Hybrid Fiber Coaxial (HFC) network, in a long amplifier cascade scenario
(e.g., N+7, N+5), nodes and amplifiers could have up to 20dB of output level range. In a fiber deep scenario, there could still be a few dB of range. However even in a scenario in which the actual output level is a few dBs (e.g., 3dB) lower than the maximum output level specified, significant power can be reduced but still maintain sufficient performance for the application if we have the mechanisms to measure the composite power and to vary the bias current to the PA in the field.

    The Adaptive Power System Interface Specification (APSIS) group has specified a power saving function called the Reduction in Bandwidth. This function is designed to reduce the Quadrature Amplitude Modulation (QAM) channel count during low traffic periods. The composite power will be reduced as a result of the QAM channel count is reduced. It is therefore possible to save the power for HFC nodes and amplifiers if there are mechanisms to measure the composite power and to vary the bias current to PA in field.

    The thermal dissipation will be the significant challenge for new HFC products under development because higher output RF power is required and more functionalities are added. Hence, if new HFC products are designed with the bias current adjustment feature, this can help prote...