Load-Modulated Power Amplifier With Envelope-Controlled Impedance
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Solution Overview
Problem
Existing power amplifiers in RF communication systems face challenges in achieving high efficiency over a wide dynamic range, particularly in modulating load impedance to match varying RF signal envelopes.
Innovation Solution
The implementation of a load modulated power amplifier system that includes a power amplifier and a controllable load impedance, where the envelope signal controls the impedance of the controllable load impedance to modulate the load at the output of the power amplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If envelope tracking amplifiers are used to achieve high efficiency over wide dynamic range, then amplification efficiency is improved, but device complexity increases
Solution Approach 1:
The patent extracts the load modulation function from a complete envelope tracking system, using only the essential controllable load impedance element rather than the full envelope tracking architecture. This selective extraction maintains efficiency benefits while reducing overall system complexity.
Solution Approach 2:
Instead of controlling the power amplifier's input or supply voltage as in conventional envelope tracking, this patent inverts the approach by controlling the load impedance at the output. This reverse control method achieves similar efficiency improvements with simpler circuitry.
2Use of energy by moving object
If load impedance modulation is implemented to match varying RF signal envelopes, then amplification efficiency is improved, but circuit complexity increases
Solution Approach 1:
The controllable load impedance circuit serves multiple functions simultaneously: it modulates load impedance to match the RF signal envelope for efficiency improvement, while also providing output matching and potential bandwidth control. This multi-functionality reduces the need for separate circuits.
Solution Approach 2:
The patent changes the impedance parameter of the load dynamically using a controllable element (such as a variable capacitor or transistor-based impedance controller) that adjusts its value in response to the RF signal envelope, enabling efficient operation across varying power levels without complex switching networks.
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 provides high efficiency power amplifiers that are less complex than envelope tracking amplifiers, while effectively leveraging circuitry for generating and calibrating the envelope signal, thereby achieving efficient amplification across a wide dynamic range.
Implementation Method 1
The envelope signal is operable to control an impedance of the controllable load impedance to modulate a load at the output of the power amplifier
Data Source
AI summary
Apparatus and methods for load modulated power amplifiers are provided. In certain embodiments, a load modulated power amplifier system includes a power amplifier that receives a radio frequency signal at an input and provides an amplified radio frequency signal at an output, and a controllable load impedance coupled to the output of the power amplifier. The controllable load impedance receives an envelope signal that changes in relation to an envelope of the radio frequency signal, and the envelope signal is operable to control an impedance of the controllable load impedance to modulate a load at the output of the power amplifier.