Push-Pull Power Amplifier Load Modulation for Balun Leakage
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Solution Overview
Problem
Conventional power amplifiers, such as push-pull power amplifiers, suffer from inefficiencies due to leakage inductance in baluns, leading to non-linear gain and reduced power-added efficiency, especially at saturated power points, which affects their performance metrics like AMAM and PAE.
Innovation Solution
Incorporating a controllable load, such as a switch or variable resistance, coupled with capacitors to balance the leakage inductance of the balun, and varying this load through a control signal to modulate the impedance, thereby improving gain and efficiency by adjusting the collector impedances of driver stages in an out-of-phase relationship.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional push-pull power amplifiers use fixed balun with leakage inductance, then the amplifier can be manufactured with simple structure, but the gain becomes non-linear and power-added efficiency decreases at saturated power points
Solution Approach 1:
The patent applies dynamics by making the balun impedance variable rather than fixed. A voltage-controlled switch (VCS) is introduced to dynamically adjust the effective inductance of the balun, allowing the impedance to adapt to different operating conditions. This dynamic adjustment enables linear gain across the operating range while maintaining manageable structural complexity through controlled variability.
Solution Approach 2:
The patent changes the impedance parameter of the balun from a fixed value to a variable value controlled by a voltage signal. By modifying the inductance parameter through the VCS and associated capacitors, the system achieves improved gain linearity and power-added efficiency. The parameter change transforms the balun from a static component to an adaptive element that optimizes performance across different power levels.
2Power
If conventional power amplifiers operate at saturated power points, then maximum power output is achieved, but power-added efficiency significantly decreases due to balun leakage inductance
Solution Approach 1:
The patent implements feedback by using a voltage-controlled switch whose control voltage is derived from the amplifier's operating conditions. The VCS adjusts the balun impedance in response to the signal level, providing automatic compensation for efficiency losses at saturated power points. This feedback mechanism ensures that the balun operates optimally across the entire power range, maintaining high power-added efficiency even at maximum output.
Solution Approach 2:
The dynamic adjustment of balun impedance through the voltage-controlled switch allows the system to adapt to varying power levels. At saturated power points, the dynamic impedance transformation compensates for the inherent losses in the balun, maintaining high power-added efficiency. The dynamic behavior enables the system to extract maximum power while minimizing energy loss through adaptive impedance matching.
3Device complexity
If fixed impedance balun is used in power amplifier, then circuit design is simplified, but AMAM performance and power-added efficiency are degraded
Solution Approach 1:
The patent changes the impedance parameter of the balun from fixed to variable, controlled by voltage signals. This parameter change enables the system to achieve superior AMAM performance and power-added efficiency. The variable impedance allows the balun to adapt to different operating conditions, transforming it from a limiting component into an optimizing element despite the increased circuit complexity.
Solution Approach 2:
The voltage-controlled switch acts as an intermediary element between the fixed circuit components and the variable impedance requirement. By introducing this intermediate device, the system achieves variable balun impedance without fundamentally redesigning the entire amplifier architecture. The VCS mediates between the simple fixed structure and the performance requirements, enabling parameter adaptation while maintaining reasonable design complexity.
Data Source
AI summary
Aspects of the disclosure include a power amplifier comprising an input to receive an input signal, an output to provide an amplified output signal, a balun coupled between the input and the output, at least one capacitor coupled to the balun, and a controllable load coupled to the at least one capacitor.