RF Power Amplifier Impedance Matching for Back-Off Efficiency
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Solution Overview
Problem
Conventional RF power amplifiers experience significant decreases in Power Added Efficiency (PAE) and increased power consumption when operating in a power back-off state, particularly in mobile communication systems like 5G NR, due to high Peak to Average Power Ratio (PAPR), which requires improved impedance management and efficiency.
Innovation Solution
A radio frequency power amplifier design incorporating a main amplifier, main matching circuit, auxiliary amplifier, auxiliary matching circuit, and impedance conversion circuit, with impedance matching circuits configured to adjust phases and raise output impedances, effectively increasing the impedance at the combining node to improve efficiency and reduce loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power amplifier operates in a power back-off state to maintain high linearity, then the linearity requirement is met, but the power added efficiency decreases significantly
Solution Approach 1:
The power amplifier is divided into two separate amplifiers: a main amplifier that operates in a power back-off state to maintain high linearity, and an auxiliary amplifier that operates at high efficiency. This segmentation allows each amplifier to operate in its optimal efficiency region while collectively meeting the overall linearity and power requirements.
Solution Approach 2:
The main amplifier and auxiliary amplifier are combined through their output signals at a combining node. The main amplifier handles the linearization function while the auxiliary amplifier supplements the output power, merging their contributions to achieve both high linearity and high power added efficiency simultaneously.
2Power
If the output impedance of the amplifier is low, then the amplifier can deliver high power, but the impedance at the combining node is insufficient, increasing loss
Solution Approach 1:
Impedance matching circuits are introduced as intermediary components between the amplifiers and the combining node. These matching circuits transform the low output impedance of the amplifiers to a higher impedance level at the combining node, reducing signal loss while maintaining the high power delivery capability.
Solution Approach 2:
The impedance matching circuits change the impedance parameter from low (at the amplifier output) to high (at the combining node). This parameter transformation optimizes the power transfer efficiency and reduces energy loss in the output circuit.
3Productivity
If complex modulation schemes are adopted to improve spectrum utilization, then the data capacity and transmission rate increase, but the Peak to Average Power Ratio increases, requiring higher linearity
Solution Approach 1:
The system segments the amplification function into two specialized amplifiers: one dedicated to maintaining linearity for complex modulation schemes, and another dedicated to providing high efficiency. This allows the system to support high data capacity modulation while meeting the stringent linearity requirements.
Solution Approach 2:
The system changes the operating parameters of the two amplifiers differently: the main amplifier operates with higher linearity to handle the complex modulation, while the auxiliary amplifier operates at higher efficiency to compensate for the power back-off, collectively supporting high data capacity transmission.
Data Source
AI summary
A radio frequency power amplifier includes a main amplifier, a main matching circuit, an auxiliary amplifier, an auxiliary matching circuit and an impedance conversion circuit. The main amplifier is configured to output a first amplified signal. The main matching circuit is connected between the main amplifier and a combining node, including at least one-stage impedance matching circuit and is configured to adjust a phase of the first amplified signal and raise an output impedance of the main amplifier to a first impedance. The auxiliary amplifier is configured to output a second amplified signal. The auxiliary matching circuit is connected between the auxiliary amplifier and the combining node, including a multi-stage impedance matching circuit and is configured to adjust a phase of the second amplified signal and raise an output impedance of the auxiliary amplifier to a second impedance. The impedance conversion circuit is connected to the combining node.