RF Amplifier Supply and Load Modulation for Peak Efficiency
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Solution Overview
Problem
Designing a satisfactory radio-frequency power amplifier for electronic devices is challenging, especially in efficiently amplifying signals over varying power levels without compromising efficiency.
Innovation Solution
The implementation of a load modulated radio-frequency amplifier circuit with an adjustable load impedance, coupled with supply modulation and load modulation circuitry, allows for dynamic adjustment of the power supply voltage and load control signal based on the baseband signal and envelope signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional fixed-power amplifiers are used, then the circuit design is simple, but the amplifier efficiency deteriorates when operating at varying power levels
Solution Approach 1:
The patent applies dynamics by making the load impedance adjustable rather than fixed. The load modulation circuitry dynamically adjusts the load impedance seen by the amplifier core based on the envelope signal, allowing the amplifier to maintain optimal efficiency across varying power levels. This transforms a static system into a dynamic one that adapts to changing operating conditions.
Solution Approach 2:
The patent changes the load impedance parameter dynamically through load modulation circuitry that adjusts the load based on the envelope signal. Additionally, the supply voltage parameter is changed through envelope tracking that modulates the power supply voltage according to the signal envelope, enabling the amplifier to operate efficiently across different power levels.
2Loss of energy
If load modulation with adjustable load impedance is implemented, then amplifier efficiency is improved across varying power levels, but the device complexity increases
Solution Approach 1:
The patent segments the amplifier system into distinct functional blocks: an amplifier core, separate load modulation circuitry, and supply modulation circuitry. This segmentation allows each block to be optimized independently and simplifies the overall design by distributing complexity across modular components rather than requiring a completely redesigned integrated system.
3Measurement precision
If envelope tracking with full bandwidth is used, then signal fidelity is maintained, but the bandwidth requirements for power supply modulation increase
Solution Approach 1:
The patent applies partial action by using a reduced bandwidth envelope signal for load modulation purposes. The load shaping circuit processes a bandwidth-reduced version of the envelope signal, which is sufficient for controlling the load impedance without requiring the full bandwidth of the original envelope signal. This partial action approach maintains adequate signal fidelity while reducing the bandwidth burden on the power supply modulation system.
Data Source
AI summary
An electronic device may include wireless circuitry. The wireless circuitry may include a radio-frequency amplifier having a data input configured to receive a radio-frequency signal generated from a baseband signal, supply modulation blocks configured to output a power supply voltage, derived from the baseband signal, for powering the radio-frequency amplifier, and load modulation blocks configured to output a load control signal, derived from the baseband signal and a bandwidth reduced envelope signal output from the supply modulation circuitry, for tuning an adjustable load component of the radio-frequency amplifier. The supply modulation blocks can include a full envelope generator, a bandwidth reduction block for outputting the bandwidth reduced envelope signal, an envelope shaping block, and an envelope tracker. The load modulation blocks can include an inverse amplifier gain model and a load shaping block.