Load Modulation Amplifier With Dynamic Peak Impedance at mmWave
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Solution Overview
Problem
Doherty power amplifiers experience efficiency degradation at high frequencies, particularly in 5G wireless network millimeter wave frequencies, due to parasitic capacitance and inductance, and struggle with output power linearity and cost complexity, making them unsuitable for phased array applications without digital pre-distortion.
Innovation Solution
A load modulation amplifier with a carrier amplifier and a peak amplifier coupled in parallel, featuring an output quadrature coupler and a matching network that increases the output impedance of the peak amplifier monotonically with increasing output power, allowing efficient power steering from the carrier to the peak amplifier without digital pre-distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Doherty power amplifier is used to improve high power backed off efficiency, then efficiency is improved, but performance degrades at high frequencies due to parasitic capacitance and inductance
Solution Approach 1:
The amplifier is segmented into a carrier amplifier and a peak amplifier that operate in different power ranges. The carrier amplifier handles low to medium power levels while the peak amplifier handles high power levels, allowing each amplifier to be optimized for its specific operating range and reducing the impact of parasitic effects at high frequencies.
Solution Approach 2:
The output impedance of the peak amplifier is designed to dynamically increase with increasing output power. This dynamic impedance modulation enables efficient power transfer across different power levels while compensating for frequency-dependent parasitic effects, maintaining performance at millimeter wave frequencies.
2Power
If Doherty power amplifier is used for high power amplification, then output power is increased, but output power linearity deteriorates
Solution Approach 1:
The invention changes the operating parameters of the two amplifiers differently based on input power level. The carrier amplifier operates in a linear region at lower powers, while the peak amplifier is biased to operate efficiently at high powers. The dynamic impedance transformation ensures that the combined output maintains linearity across the full power range without requiring digital pre-distortion.
3Manufacturing precision
If digital pre-distortion is applied to correct non-linear Doherty operation, then linearity is improved, but complexity and cost increase
Solution Approach 1:
The amplifier system achieves linearity through its inherent design rather than external correction. The dynamic impedance modulation and dual-amplifier architecture automatically compensate for non-linearities, allowing the system to self-correct without requiring digital pre-distortion processing, thereby reducing complexity and cost.
4Power
If Doherty power amplifier is used for phased array applications, then output power capability is improved, but cost and complexity increase
Solution Approach 1:
The phased array system uses multiple instances of this simplified two-amplifier architecture rather than complex single-amplifier solutions. Each amplifier module is independently designed with carrier and peak amplifiers, allowing modular deployment that scales with array size while maintaining manageable complexity at each node.
Data Source
AI summary
A load modulation amplifier is disclosed. The load modulation amplifier includes a carrier amplifier for amplifying a radio frequency signal when input power of the radio frequency signal is below a predetermined power threshold value and a peak amplifier coupled in parallel with the carrier amplifier for amplifying the radio frequency signal when input power of the radio signal is above the predetermined power threshold value. The load modulation amplifier further includes an output quadrature coupler configured to combine power from both the carrier amplifier and the peak amplifier for output through an output load terminal. Output impedance of the peak amplifier monotonically increases with increasing output power at the output load terminal.