Outphasing Power Amplifier Impedance Matching for Back-Off Efficiency
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Solution Overview
Problem
Current power amplifiers face challenges in achieving high efficiency and linearity due to increased signal peak-to-average ratio in modern wireless communication systems, leading to complex circuit designs and debugging difficulties, especially with switching mode power amplifiers that require harmonic control.
Innovation Solution
The outphasing power amplifier employs a signal component separator, multiple power amplifier branches, and a combiner with input and output matching circuits to maintain high efficiency by matching impedances corresponding to peak and average output powers, simplifying the circuit design and reducing the need for harmonic control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If complex digital modulation techniques with multicarrier configuration are used to achieve higher data transmission rate, then data transmission rate is improved, but signal peak-to-average ratio increases making it difficult to achieve high efficiency
Solution Approach 1:
The power amplifier is divided into multiple parallel branches (at least two), each handling a portion of the modulated signal. This segmentation allows each branch to operate more efficiently while collectively maintaining the required data transmission rate, thereby resolving the contradiction between high data rate and power efficiency.
Solution Approach 2:
The patent implements dynamic impedance matching that automatically adjusts to maintain optimal operating conditions across varying signal conditions. The system dynamically adapts the impedance transformation ratio based on the signal's peak-to-average ratio, enabling the power amplifier to maintain high efficiency even when handling complex modulation schemes with varying power levels.
2Use of energy by moving object
If switching mode power amplifiers are used to achieve high efficiency, then power amplifier efficiency is improved, but linearity becomes difficult to maintain
Solution Approach 1:
By segmenting the signal across multiple parallel power amplifier branches, each operating in switching mode for high efficiency, the patent maintains overall signal linearity through coherent combination. The segmentation allows non-linear switching amplifiers to be used while preserving linearity at the output through proper phase and amplitude control of each branch.
Solution Approach 2:
Multiple parallel power amplifier branches are merged at the output through a combiner network. This merging process combines the outputs of individual switching-mode amplifiers in such a way that the overall system maintains linearity while each individual amplifier operates in the efficient switching mode, thus resolving the contradiction between efficiency and linearity.
3Reliability
If harmonic control is implemented in switching mode power amplifiers to maintain linearity, then signal linearity is improved, but circuit design complexity increases
Solution Approach 1:
The patent extracts and removes the complex harmonic control circuits from the traditional switching mode power amplifier design. By using parallel branches with simplified impedance matching networks instead of complex harmonic control, the system achieves the required linearity without the burden of complex harmonic management circuitry, thereby reducing overall design complexity.
Solution Approach 2:
The patent introduces intermediate impedance matching networks as mediators between the switching mode power amplifiers and the load. These intermediary networks simplify the overall circuit design by handling impedance transformation and signal combining functions, replacing the need for complex direct harmonic control circuits while maintaining signal linearity.
4Power
If impedance matching is optimized for peak output power, then maximum output power is achieved, but efficiency at average power levels decreases
Solution Approach 1:
The patent implements dynamic impedance matching that automatically adjusts the impedance transformation ratio based on the signal's instantaneous power level. When the signal is at peak power, the matching network optimizes for maximum power transfer; when the signal is at average power levels, it dynamically adjusts to maintain optimal efficiency, thus resolving the contradiction between peak power and average efficiency.
Solution Approach 2:
The system changes the impedance matching parameters dynamically based on operating conditions. By adjusting the impedance transformation ratio and other matching parameters according to whether the amplifier is operating at peak or average power levels, the patent achieves both maximum output power capability and high efficiency at average power operation.
Data Source
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AI summary
An out-of-phase power amplifier and a method for realizing output matching therefor, comprising: calculating an offset angle of a combiner according to signal power back-off of a signal source, i.e., a signal peak-to-average ratio; determining, according to the calculated offset angle, a ratio of optimal impedance Zm1 corresponding to a peak output power of a power tube to optimal impedance Zm2 corresponding to a mean output power of the power tube, wherein the ratio is a standing-wave ratio; determining, according to the size of an isostatic standing-wave ratio circle, a maximum power point impedance Zopt of the power tube by means of a load pull mode; by taking the maximum power point impedance Zopt as a reference point, finding out a back-off high-efficiency point impedance Zbk_eff on the isostatic standing-wave ratio circle; and matching the maximum power point impedance Zopt and the back-off high-efficiency point impedance Zbk eff, as corresponding impedance values, respectively to two input ends of the combiner.