Doherty Amplifier Phase Compensation for Peaking Impedance Variation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Doherty amplifiers face challenges in achieving high efficiency and linearity due to significant non-linear input impedance variations in peaking amplifiers, leading to AM/PM distortion and reduced power performance.
Innovation Solution
A phase distortion compensation circuit using a Pi-network and control load circuit is implemented to absorb non-linear input impedance variations, providing phase pre-distortion between peaking amplifiers and maintaining phase consistency with the carrier amplifier, thereby enhancing efficiency and reducing AM/PM distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Doherty amplifiers use transistors with high theoretical power efficiency, then power efficiency is improved, but linearity deteriorates due to significant non-linear input impedance variations
Solution Approach 1:
The patent applies preliminary action by implementing a phase pre-distortion circuit that anticipates and compensates for non-linear input impedance variations before they cause distortion. The circuit calculates correction values based on expected operating conditions and applies phase corrections in advance, preventing AM/PM distortion rather than correcting it after occurrence. This allows the amplifier to maintain both high efficiency and linearity by pre-adjusting the phase characteristics.
2Reliability
If phase distortion compensation circuitry is added to improve linearity, then linearity is improved, but device complexity increases
Solution Approach 1:
The patent implements parameter changes by dynamically adjusting phase shift values based on operating conditions. The phase pre-distortion circuit modifies phase parameters in response to detected input impedance variations, allowing the system to adapt to different power levels and loading conditions. This dynamic parameter adjustment achieves improved linearity without requiring a completely complex fixed circuit architecture, as the same circuit can adapt its behavior based on real-time conditions.
3Reliability
If input impedance variations are compensated to reduce AM/PM distortion, then linearity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs feedback mechanisms where the phase pre-distortion circuit continuously monitors operating conditions and adjusts phase corrections accordingly. By detecting actual performance deviations and applying compensatory phase adjustments, the system can achieve consistent linearity performance without requiring extremely tight manufacturing tolerances. The feedback loop masks the effects of manufacturing variations through active compensation.
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
The embodiments described herein include amplifiers (100) that are typically used in radio frequency (RF) applications. Specifically, the amplifiers (100) described herein include a phase distortion compensation circuit (108) that can compensate for input impedance variations that could otherwise lead to reduced efficiency and power performance. In one specific embodiment, the phase distortion compensation circuit (108) is used to compensate for input impedance variations in the peaking amplifiers (104,106) of a Doherty amplifier (100). In such embodiments, the phase distortion compensation circuit (108) can absorb the non-linear input impedances of the peaking amplifiers (104, 106) in a way that may facilitate improved phase maintenance between the carrier and peaking stages of the Doherty amplifier (100).