Power Amplifier Bias Correction for Duty-Cycle DEVM Control

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Solution Overview

Problem

Power amplifiers in RF systems face challenges in maintaining constant gain and phase as duty cycles change, leading to dynamic error vector magnitude (DEVM) issues due to self-heating effects, which previous compensation methods fail to address effectively.

Innovation Solution

A bias circuit and low pass filter system that generates a correction signal based on the duty cycle of the amplifier, adjusting the bias signal to maintain constant gain and phase by integrating the enable signal, thereby compensating for DEVM across varying operating conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the amplifier operates at high duty cycles, then the output power increases, but the self-heating effects cause gain and phase variations leading to DEVM degradation

Engineering Contradiction:

Improveoutput powerVSAvoidgain and phase stability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent implements a feedback mechanism where the bias circuit monitors the duty cycle of the amplifier and dynamically adjusts the bias signal in response. The low pass filter processes the duty cycle signal to generate a correction component that feeds back to the bias circuit, creating a closed-loop system that compensates for thermal effects and maintains stable gain and phase across varying duty cycles

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the bias parameter dynamically based on duty cycle variations. By adjusting the bias signal according to the duty cycle, the system adapts to thermal conditions caused by different power levels, thereby maintaining consistent amplifier performance across varying operating conditions

Inventive Principle:

Principle #35Parameter changes

2Power

If the bias signal is increased to maintain gain at high duty cycles, then the amplifier output power is maintained, but the phase stability deteriorates

Engineering Contradiction:

Improveamplifier output powerVSAvoidphase stability

Core Design Contradiction:

PowerVSStability of the object's composition

Solution Approach 1:

The patent transitions from a static bias approach to a dynamic bias adjustment system. The bias circuit continuously adapts the bias signal based on real-time duty cycle information processed through the low pass filter, enabling the system to maintain both power output and phase stability under varying operating conditions rather than optimizing for one condition only

Inventive Principle:

Principle #15Dynamics

3Measurement precision

If previous compensation methods are used, then some DEVM correction is achieved, but the correction is not effective across varying duty cycles

Engineering Contradiction:

ImproveDEVM correction accuracyVSAvoidduty cycle adaptability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent implements a dynamic compensation mechanism that adapts to varying duty cycles. Unlike fixed compensation methods, the bias circuit continuously adjusts the bias signal based on the actual duty cycle, making the DEVM correction effective across the full range of operating conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent uses feedback from the duty cycle signal to dynamically adjust the bias correction. The low pass filter processes the duty cycle information and feeds it back to the bias circuit, creating an adaptive system that maintains accurate DEVM correction regardless of duty cycle variations

Inventive Principle:

Principle #23Feedback

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

The solution effectively reduces DEVM by adjusting the bias signal inversely proportional to duty cycle changes, mitigating thermal effects and maintaining amplifier performance across different operating conditions.

Implementation Method 1

integrating an indication of a duty cycle of the amplifier to generate a dynamic correction signal

Methodology Applied

Scientific EffectIntegration:

Implementation Method 2

A bias circuit and low pass filter system that generates a correction signal based on the duty cycle of the amplifier

Methodology Applied

Scientific EffectLow pass filtering: Filter (electronic)

Implementation Method 3

mitigating thermal effects and maintaining amplifier performance across different operating conditions

Methodology Applied

Scientific EffectThermal effects compensation:

Data Source

PatentUS10236829B2Dynamic error vector magnitude duty cycle correction

Publication Date: 2019.03.19 SKYWORKS SOLUTIONS INC

AI summary

Aspects of this disclosure relate to dynamic error vector magnitude (DEVM) compensation. In one embodiment, an apparatus includes an amplifier, a low pass filter, and a bias circuit. The amplifier, such as a power amplifier, can amplify an input signal. The low pass filter, such as an integrator, can generate a correction signal based at least partly on an indication of a duty cycle of the amplifier. The indication of the duty cycle of the amplifier can be an enable signal for the amplifier, for example. The bias circuit can generate a bias signal based at least partly on the correction signal and provide the bias signal to the amplifier to bias the amplifier.