Embedded RF Cable-Loss Compensation for Long TDD Radio Links

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Solution Overview

Problem

Wireless communication devices face significant challenges due to RF cable losses, which reduce achievable wireless range and coverage, and existing solutions like using low-loss RF cables or physically integrating antennas with radios are costly and impractical, especially for long cable lengths and outdoor applications.

Innovation Solution

A cable-loss compensation system that uses a compensator circuit to provide precise timed low-noise receive amplification and high transmit power output, allowing antennas to be located tens of meters from radios with minimal performance degradation, while using standard RF cables and requiring only DC power and RF signaling, thus being cost-effective and flexible.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If standard RF cables are used to connect antennas and radios over long distances, then installation flexibility and cost are improved, but cable loss increases significantly reducing wireless range and coverage

Engineering Contradiction:

Improveinstallation flexibility and costVSAvoidcable loss

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The system performs preliminary measurement of cable loss during a calibration phase before normal operation. The radio transmits test signals through the cable and measures the received signal strength to determine the actual cable loss characteristics. This pre-characterization enables the system to compensate for the measured loss during subsequent communication operations, allowing standard cables to be used effectively over long distances without sacrificing performance.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts transmission power and receiver gain parameters based on the measured cable loss. By changing these operational parameters in response to the specific cable characteristics, the system compensates for cable attenuation and maintains optimal communication performance despite using standard, lossy cables over extended distances.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If low-loss RF cables are used to reduce cable loss, then wireless range and coverage are improved, but system cost increases significantly

Engineering Contradiction:

Improvecable lossVSAvoidsystem cost

Core Design Contradiction:

Loss of energyVSEase of manufacture

Solution Approach 1:

The system replaces expensive, specialized low-loss RF cables with inexpensive standard RF cables. By using readily available, cheaper cable components and compensating for their higher loss through electronic measurement and parameter adjustment, the system achieves comparable performance at significantly reduced cost, treating the cable as a commodity component rather than a critical performance-determining element.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Loss of energy

If antennas are physically integrated with radios to eliminate cable loss, then RF performance is improved, but device complexity and installation flexibility worsen

Engineering Contradiction:

Improvecable lossVSAvoidintegration complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The system maintains the segmented architecture of separate radios and antennas connected by cables, rather than forcing physical integration. By keeping the components separate and using electronic compensation techniques to measure and correct for cable loss, the system achieves performance comparable to integrated designs while preserving the advantages of modular installation and independent optimization of radio and antenna components.

Inventive Principle:

Principle #1Segmentation

4Area of stationary object

If cable length is increased to extend wireless coverage area, then service area is improved, but cable loss increases reducing system performance

Engineering Contradiction:

Improvewireless coverage areaVSAvoidcable loss

Core Design Contradiction:

Area of stationary objectVSLoss of energy

Solution Approach 1:

The system implements a feedback mechanism where the radio continuously monitors signal strength and quality after transmission through the cable. Based on this feedback information, the system adjusts transmission power, receiver sensitivity, and other parameters to compensate for the cumulative cable loss. This closed-loop control enables the system to extend coverage area using long cables while maintaining acceptable performance through real-time adaptation to the actual signal conditions.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11546015B1Cable loss compensation system for time domain duplexed (TDD) radios using embedded radio frequency (RF) control

Publication Date: 2023.01.03 AMAZON TECH INC

AI summary

Technologies directed to cable-loss compensation are described. An apparatus includes a triplexer, a front-end module (FEM) circuit, and a control circuit. The triplexer is coupled to a radio frequency (RF) cable. The triplexer receives a first RF signal and a DC power signal from a device via the RF cable and sends a detection signal being indicative of a transmit power level of the first RF signal to the device via the RF cable. The transmit power level includes an insertion loss of the RF cable. The FEM circuit is coupled to the triplexer and includes a power amplifier (PA). The control circuit is coupled to the triplexer and measures the transmit power level of the first RF signal and converts the first RF signal into the detection signal. The control circuit sends the detection signal back to the device via the RF cable and enables the PA.