Doherty RF Amplifier Peaking Path Impedance Tuning for Distortion
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Solution Overview
Problem
Doherty RF amplifier circuitry generates significant distortion when the peaking amplifier path becomes active due to parasitic impedances, which existing linearization techniques often fail to adequately compensate.
Innovation Solution
Incorporating a peaking variable gain preamplifier that adjusts the current provided to the peaking amplifier, allowing for adjustment of the output impedance presented to the main amplifier path, thereby reducing distortion when the peaking amplifier path is activated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the peaking amplifier path is activated to increase output power, then the power amplification capability is improved, but significant distortion is generated due to parasitic impedances
Solution Approach 1:
The patent changes the operating parameters of the peaking amplifier path by adjusting its output impedance through a variable gain preamplifier. This parameter adjustment allows the peaking amplifier to operate more linearly across different power levels, reducing distortion while maintaining high power amplification capability when activated
Solution Approach 2:
The patent introduces dynamic control of the peaking amplifier path by using a variable gain preamplifier that adjusts the output impedance in real-time based on operating conditions. This dynamic adjustment optimizes the performance of the peaking amplifier path, reducing distortion during activation while preserving power amplification capability
2Reliability
If digital predistortion is used to compensate for distortion, then linearity is improved, but the distortion may still be too large for adequate compensation
Solution Approach 1:
The patent applies preliminary action by adjusting the output impedance of the peaking amplifier path before the signal undergoes significant distortion. The variable gain preamplifier proactively optimizes the operating conditions of the peaking amplifier, preventing excessive distortion from occurring in the first place, thereby reducing the burden on digital predistortion techniques
Data Source
AI summary
Doherty radio frequency (RF) amplifier circuitry includes an input node, an output node, a main amplifier path, and a peaking amplifier path. The main amplifier path is coupled between the input node and the output node and includes a main amplifier. The peaking amplifier path is coupled in parallel with the main amplifier path between the input node and the output node, and includes a peaking amplifier and a peaking variable gain preamplifier between the input node and the peaking amplifier. The peaking variable gain preamplifier is configured to adjust a current provided to the peaking amplifier.