Line Amplifier Gain Control Using Pilot Signals

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Solution Overview

Problem

Current line amplifiers in leaky coaxial cable networks face challenges with manual gain control due to human error and accessibility issues, and automatic gain control is compromised by fluctuations in voice channel activity, leading to inefficient signal amplification and potential network failure.

Innovation Solution

A gain control system that transmits a low-level pilot signal in pulses on an unused channel frequency to adjust the amplifier gain, ensuring the pilot signal level is lower than voice channel signals, allowing for efficient and stable gain adjustment regardless of the number of active voice channels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If manual gain control is used on line amplifiers, then the amplifier gain can be adjusted, but human error and accessibility issues lead to unreliable gain settings and potential network failure

Engineering Contradiction:

Improvegain setting reliabilityVSAvoidaccessibility for manual adjustment

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The line amplifier automatically adjusts its own gain setting by receiving pilot signals, measuring output levels, and modifying gain without human intervention. This self-service mechanism eliminates the need for manual access to amplifiers located in difficult-to-reach areas while ensuring reliable gain control through automated feedback control.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system implements feedback control by measuring the actual output signal level of the amplifier and comparing it to a desired level, then automatically adjusting the gain setting based on the measured deviation. This closed-loop feedback ensures reliable gain control regardless of manual adjustment difficulties.

Inventive Principle:

Principle #23Feedback

2Extent of automation

If automatic gain control is implemented using existing voice channel signals, then gain adjustment is automated, but fluctuations in voice channel activity cause unstable gain settings and inefficient signal amplification

Engineering Contradiction:

Improvegain control automationVSAvoidgain setting stability

Core Design Contradiction:

Extent of automationVSStability of the object's composition

Solution Approach 1:

A dedicated pilot signal acts as an intermediary for gain control measurements, separate from the voice channel signals. This pilot signal provides a stable, controlled reference that is not affected by variations in voice traffic, enabling automated gain control while maintaining stability. The pilot signal is specifically designed for measurement purposes and transmitted at a known level.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system segments the control function from the data function by using separate pilot signals dedicated solely for gain control measurements, distinct from the voice channel signals used for communication. This segmentation allows the gain control mechanism to operate independently of voice traffic variations, ensuring stable automated control.

Inventive Principle:

Principle #1Segmentation

3Stability of the object's composition

If pilot signals are transmitted continuously to maintain stable gain control, then gain setting stability is improved, but power consumption increases and interference with voice channels occurs

Engineering Contradiction:

Improvegain control stabilityVSAvoidpilot signal power consumption

Core Design Contradiction:

Stability of the object's compositionVSUse of energy by moving object

Solution Approach 1:

The pilot signal is transmitted periodically at predetermined time intervals rather than continuously. This periodic transmission maintains adequate signal stability for gain control measurements while significantly reducing power consumption compared to continuous transmission. The interval is optimized to provide sufficient measurement accuracy without excessive energy use.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The pilot signal is transmitted at a level that is sufficient for accurate gain control measurements but deliberately kept lower than voice channel signals to minimize interference and power consumption. This partial action approach provides just enough signal strength for control purposes without the excessive power expenditure of full-strength continuous signaling.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11601103B2Channelised gain control of line amplifiers

Publication Date: 2023.03.07 RF IND

AI summary

A method for controlling gain of a line amplifier on a cable, the method comprising selecting an unused carrier frequency; transmitting a pulsed pilot signal on the unused carrier frequency into the cable; determining a pilot signal output strength by measuring signal strength of the pilot signal after amplification by the line amplifier; comparing the pilot signal output strength with a target signal strength to determine a difference; and adjusting the gain of the line amplifier corresponding to the difference.