Wideband Doherty Amplifier Harmonic Injection for Back-Off Efficiency
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Solution Overview
Problem
Doherty power amplifiers face challenges in maintaining high efficiency over a wide frequency range due to high peak to average power ratios in modern wireless communication devices, particularly with the use of multi-input multi-output and carrier aggregation techniques, leading to issues with output back-off range, linearity, and operating bandwidth.
Innovation Solution
A Doherty power amplifier design featuring a main and auxiliary power amplification device in parallel, with a load modulation circuit that includes a harmonic injection circuit providing phase shift and a phase compensation circuit, allowing for efficient transfer of second harmonic components and compensating inherent phase differences between the devices, optimized for deep Class AB and Class C amplifier operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional Doherty power amplifier design is used, then the amplifier can operate at saturation, but efficiency deteriorates over wide frequency range due to high PAPR and multi-input multi-output techniques
Solution Approach 1:
The patent applies preliminary action by pre-compensating phase differences between main and auxiliary amplification devices using a phase compensation circuit. This circuit is designed to counteract the inherent phase shifts that occur during wideband operation, ensuring that second harmonic components are properly transferred between devices before they cause efficiency degradation. The phase compensation is built into the amplifier architecture rather than added as a separate correction step.
Solution Approach 2:
The patent uses an intermediary approach by introducing a dedicated phase compensation circuit as a mediator between the main and auxiliary power amplification devices. This intermediary circuit specifically addresses the phase mismatch problem that arises in wideband Doherty amplifiers, allowing the second harmonic transfer mechanism to function correctly across the operating bandwidth without directly modifying the main amplification path.
2Loss of energy
If second harmonic transfer is implemented between main and auxiliary devices, then efficiency is improved, but phase differences between devices cause performance degradation
Solution Approach 1:
The phase compensation circuit serves as an intermediary element that mediates the phase relationship between main and auxiliary amplification devices. It is inserted into the signal path to actively correct phase mismatches, enabling the second harmonic transfer mechanism to operate effectively despite the inherent phase differences that exist in wideband Doherty amplifier configurations.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the phase compensation across the operating bandwidth. The phase compensation circuit is designed to provide frequency-dependent phase correction, changing its compensation characteristics to maintain optimal phase relationships as the operating frequency varies across the wideband range.
3Productivity
If deep Class AB and Class C amplifier operation is used, then output back-off range is improved, but linearity and efficiency are compromised
Solution Approach 1:
The patent converts the harmful effect of second harmonic distortion, which naturally occurs in deep Class AB and Class C amplifier operation, into a beneficial mechanism. By deliberately transferring second harmonic components between the main and auxiliary amplification devices through the load modulation circuit, the amplifier achieves improved efficiency and output back-off range while using the previously harmful harmonics to enhance performance.
Solution Approach 2:
The phase compensation circuit acts as an intermediary that enables the deep Class AB and Class C operation to maintain linearity despite the aggressive biasing conditions. It ensures that the phase relationships remain correct during the nonlinear operation modes, allowing the amplifier to achieve high output back-off range while maintaining acceptable linearity through proper harmonic transfer.
Data Source
AI summary
A Doherty power amplifier having a main power amplification device and an auxiliary power amplification device arranged in parallel with the main power amplification device includes a load modulation circuit having a harmonic injection circuit connected with respective outputs of the main power amplification device and the auxiliary power amplification device. The harmonic injection circuit is arranged to provide a phase shift to simultaneously modulate transfer of second harmonic components generated at the main power amplification device to the auxiliary power amplification device and transfer of second harmonic components generated at the auxiliary power amplification device to the main power amplification device, when the main power amplification device and the auxiliary power amplification device are operated at saturation.