Envelope Tracking Power Amplifier Control for Impedance Stability
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Solution Overview
Problem
Envelope tracking power amplifiers face instability and inefficient input-to-output response due to varying equivalent impedance levels, which affect the control loop stability and power amplifier performance.
Innovation Solution
The system dynamically adjusts control loop parameters by using an inner loop that senses and adjusts the low pass filter parameters based on instantaneous current and voltage, ensuring stable operation and improved frequency response across different loading conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If envelope tracking is used to improve power amplifier efficiency, then power consumption is reduced, but control loop instability occurs due to varying equivalent impedance levels
Solution Approach 1:
The patent applies dynamics by making the low pass filter parameters adjustable and variable rather than fixed. The filter characteristics are dynamically modified based on detected equivalent impedance levels, allowing the system to adapt to changing operating conditions and maintain stability while achieving energy efficiency through envelope tracking.
Solution Approach 2:
The patent changes physical parameters of the low pass filter (such as cutoff frequency or filter order) based on the detected equivalent impedance level. This parameter modification allows the control loop to maintain stability across different operating conditions while enabling the envelope tracking function to reduce power consumption.
2Device complexity
If fixed control loop parameters are used, then device complexity is reduced, but input-to-output response becomes inefficient under varying loading conditions
Solution Approach 1:
The patent modifies control loop parameters (specifically low pass filter characteristics) based on operating conditions without fundamentally changing the control loop structure. This approach maintains relative simplicity while significantly improving input-to-output response efficiency under varying loading conditions through adaptive parameter adjustment.
Data Source
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AI summary
An apparatus comprises an amplifier having an input coupled to a radio frequency signal through a digital-to-analog circuit, an adaptive power supply having an output coupled to a bias voltage of the amplifier, wherein the output of the adaptive power supply is configured to have a shape similar to an envelope of the radio frequency signal and a feedback circuit comprising a sensing circuit and a mapping circuit, wherein the sensing circuit is configured to sense a current flowing from the adaptive power supply to the amplifier and sense the bias voltage of the amplifier, and wherein the mapping circuit is configured to sense the bias voltage of the amplifier, and wherein the mapping circuit is configured to generate a control signal for dynamically adjusting parameters of a low pass filter so as to stabilize the adaptive power supply.