Envelope Tracking Voltage Tracker Bias Modulation Circuit
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Solution Overview
Problem
Envelope tracking (ET) voltage modulated voltages in power amplifier circuits for mobile communication devices often deviate from their target voltages due to crossover distortions, leading to compromised linearity and efficiency.
Innovation Solution
An ET voltage tracker circuit with a bias modulation circuit dynamically determines crossover distortions and adjusts the bias current to reduce deviations, ensuring the ET modulated voltage closely tracks the ET target voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If envelope tracking is used to improve power amplifier efficiency, then power dissipation is reduced, but crossover distortion causes voltage deviation from target
Solution Approach 1:
The patent implements a feedback mechanism where the bias modulation circuit continuously monitors the alternating current level in the amplifier circuit and dynamically adjusts the bias current accordingly. When the alternating current level indicates crossover distortion (between upper and lower current thresholds), the bias current is increased to compensate, ensuring the ET modulated voltage tracks the target voltage accurately while maintaining efficiency benefits
Solution Approach 2:
The patent dynamically changes the bias current parameter based on operating conditions. The bias modulation circuit adjusts the bias current level in response to alternating current measurements, modifying this critical parameter to eliminate crossover distortion while preserving the envelope tracking efficiency improvements
2Manufacturing precision
If bias current is increased to reduce crossover distortion, then voltage tracking accuracy improves, but power consumption increases
Solution Approach 1:
The patent employs dynamic bias current adjustment rather than a fixed high bias current. The bias modulation circuit continuously adapts the bias current level based on real-time alternating current measurements, increasing bias current only when crossover distortion is detected (when alternating current is between thresholds) and maintaining lower bias current when not needed, thus improving tracking accuracy only when required
Solution Approach 2:
The bias modulation operates periodically by monitoring alternating current levels and applying bias adjustments only during crossover regions. This periodic intervention approach maintains voltage tracking accuracy during critical transition periods while minimizing overall power consumption during steady-state operation
Data Source
AI summary
An envelope tracking (ET) voltage tracker circuit and related power management circuit are provided. In examples discussed herein, an amplifier circuit(s) is configured to amplify a radio frequency (RF) signal(s) based on an ET modulated voltage provided by an ET voltage tracker circuit(s). The ET voltage tracker circuit(s) includes amplifier circuitry, which operates based on an ET target voltage and a bias current to generate the ET modulated voltage. However, the ET modulated voltage may deviate from the ET target voltage from time to time due to cross over distortions. In this regard, the ET voltage tracker circuit includes a bias modulation circuit to dynamically determine the cross over distortion and adjust the bias current to reduce deviations of the ET modulated voltage. As a result, the ET modulated voltage can track the ET target voltage more closely, thus helping to improve linearity performance and efficiency of the amplifier circuit(s).