Local Oscillator Clock Shaping for PA Nonlinearity Compensation

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Solution Overview

Problem

Existing radio frequency (RF) transceivers face challenges in compensating for the non-linearity of power amplifiers, which leads to distortion and inefficiency in RF communication systems.

Innovation Solution

The implementation of local oscillator clock shaping to pre-distort radio frequency transmit signals, which compensates for the non-linearity of power amplifiers by shaping clock signals provided to the mixer in the transceiver.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If digital pre-distortion is applied to the baseband signal, then power amplifier non-linearity is compensated, but device complexity increases

Engineering Contradiction:

Improvelinearity of RF transmit signalVSAvoidcomplexity of pre-distortion circuit

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent introduces a local oscillator as an intermediary component that applies pre-distortion through its clock signals to the mixer. Instead of directly modifying the baseband signal with complex digital pre-distortion circuits, the local oscillator serves as a mediator that imparts the necessary distortion compensation through frequency upconversion, thereby reducing the complexity of the pre-distortion implementation while achieving the same linearity improvement.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the traditional digital signal processing approach (mechanical/electronic circuit modification) with a frequency domain approach. By using the local oscillator's clock signals to apply pre-distortion during frequency upconversion, the system substitutes complex time-domain digital pre-distortion circuits with a more elegant frequency-domain solution that leverages the mixer's inherent mixing function.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Loss of energy

If local oscillator clock shaping is used for pre-distortion, then power amplifier efficiency is improved, but device complexity increases

Engineering Contradiction:

Improveefficiency of power amplifierVSAvoidcomplexity of local oscillator circuit

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The local oscillator serves multiple functions: it provides the frequency upconversion signal for the mixer and simultaneously applies pre-distortion to compensate for power amplifier non-linearity. By making the local oscillator multi-functional, the patent avoids adding separate pre-distortion circuits, thereby improving power amplifier efficiency without significantly increasing device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the frequency upconversion function and the pre-distortion function into a single local oscillator component. Instead of having separate circuits for frequency synthesis and pre-distortion, the local oscillator's clock signals perform both roles, consolidating functionality and minimizing the increase in device complexity while achieving improved power amplifier efficiency.

Inventive Principle:

Principle #5Merging (Combining)

3Device complexity

If traditional mixing is used without pre-distortion, then device complexity is low, but signal distortion increases

Engineering Contradiction:

Improvesimplicity of mixing circuitVSAvoiddistortion of RF transmit signal

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The patent applies pre-distortion in advance through the local oscillator's clock signals before the signal reaches the power amplifier. By preparing the distorted clock signals that will counteract the power amplifier's non-linearity beforehand, the system maintains simple mixing circuits while eliminating signal distortion that would otherwise be generated by the power amplifier's non-linear operation.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances the linearity of the RF transmit signal, improves the efficiency of the power amplifier, and reduces distortion, thereby improving overall communication performance.

Implementation Method 1

at least one mixer configured to generate the radio frequency transmit signal based on providing frequency upconversion to at least one baseband transmit signal

Methodology Applied

Scientific EffectFrequency upconversion:

Data Source

PatentUS12328103B2Local oscillator clock shaping for pre-distortion

Publication Date: 2025.06.10 ANALOG DEVICES INC

AI summary

Apparatus and methods for pre-distorting a radio frequency transmit signal based on local oscillator clock shaping are disclosed. In certain embodiments, one or more clock signals generated by a local oscillator and used for mixing in a transceiver are shaped to account for non-linearity of a power amplifier that amplifies the radio frequency transmit signal. Such pre-distortion can be performed in addition to or alternatively to performing digital pre-distortion on a digital representation of the radio frequency transmit signal.