Low Resolution Predistorter Pacification Carrier Linearization

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current predistorters, particularly those designed for LTE signals, are not effective in handling Narrowband IoT signals due to their low resolution, leading to deteriorated output signal performance when the bandwidth is below the minimum modulation bandwidth, and developing high-resolution predistorters configured for the 900 MHz band LMR RF systems takes time, causing delays in infrastructure implementation.

Innovation Solution

A radio frequency system that includes a power amplifier and a low-resolution predistorter coupled with an electronic processor to determine the composite bandwidth of broadcast carriers and generate a pacification carrier when necessary, combining it with the carriers to increase the bandwidth above the predistorter's minimum modulation bandwidth, thereby activating the predistorter and improving signal linearization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If low-resolution predistorters are used for Narrowband IoT signals, then device complexity is reduced and implementation is accelerated, but signal linearization performance deteriorates when bandwidth is below minimum modulation bandwidth

Engineering Contradiction:

Improvepredistorter resolutionVSAvoidsignal linearization performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

A pacification carrier is introduced as an intermediary signal to bridge the bandwidth gap. The pacification carrier is injected into the narrowband signal path to artificially broaden the composite bandwidth, enabling the low-resolution predistorter to process the combined signal effectively. After predistortion, the pacification carrier is removed, leaving the original narrowband signal with improved linearization performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The bandwidth parameter of the signal is dynamically changed by adding the pacification carrier. This temporary parameter modification allows the predistorter to operate within its effective bandwidth range, and the original parameter is restored after processing by removing the pacification carrier.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If high-resolution predistorters are developed for 900 MHz band LMR RF systems, then signal linearization performance is improved, but implementation time increases causing infrastructure delays

Engineering Contradiction:

Improvesignal linearization performanceVSAvoidinfrastructure implementation time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The pacification carrier approach is prepared and implemented in advance, allowing existing low-resolution predistorters to be used immediately without waiting for high-resolution device development. This preliminary solution enables immediate infrastructure deployment while maintaining acceptable performance.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The pacification carrier is a temporary, easily implementable solution that does not require expensive high-resolution predistorters. It serves its purpose during the transition period and can be removed or adjusted as needed, avoiding the time and cost of developing specialized high-resolution equipment.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If the bandwidth of broadcast carriers is increased above minimum modulation bandwidth, then predistorter effectiveness is improved, but signal bandwidth expansion may interfere with adjacent channels

Engineering Contradiction:

Improvepredistorter effectivenessVSAvoidadjacent channel interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The pacification carrier serves as a mediator that temporarily occupies the frequency space needed for effective predistortion. It is carefully positioned and controlled to provide the necessary bandwidth for the predistorter while being removed before transmission to prevent adjacent channel interference.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The pacification carrier is added periodically or conditionally based on the detected bandwidth of the broadcast carrier. When the broadcast carrier bandwidth is sufficient, the pacification carrier is not added. When it is insufficient, the pacification carrier is added to achieve the minimum modulation bandwidth, and then removed after predistortion.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS11456760B1Linearizing narrowband carriers with low resolution predistorters

Publication Date: 2022.09.27 MOTOROLA SOLUTIONS INC

AI summary

Apparatus and method for linearizing narrowband carriers with low resolution predistorters are provided. The method includes amplifying, using a power amplifier, one or more broadcast carriers and linearizing, using a predistorter coupled to the power amplifier, the one or more broadcast carriers. The method also includes determining, using an electronic processor, a composite bandwidth of the one or more broadcast carriers and determining, using the electronic processor, whether the composite bandwidth is below a modulation bandwidth of the predistorter. The method further includes controlling, using the electronic processor, a pacification carrier generator coupled to the electronic processor to combine a pacification carrier with the one or more broadcast carriers when the composite bandwidth is below the minimum modulation bandwidth of the predistorter.