Envelope-Controlled Power Amplifier Bias for Linearity and Efficiency
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Solution Overview
Problem
Conventional power amplifiers (PAs) face challenges in achieving high efficiency and linearity, with linear PAs having poor efficiency and non-linear PAs having poor linearity, making them unsuitable for high-linearity modulation systems.
Innovation Solution
A control device and method for a PA system that preprocesses input signals by selecting modes, adjusting waveforms, generating power voltages, and setting biases based on envelope amplitudes to optimize supply voltage and input power parameters, enabling operation in both linear and non-linear switching modes for improved efficiency and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear PA system (class-A, class-B, or class-AB) is used with fixed DC bias to achieve better linearity, then linearity is improved, but efficiency deteriorates due to high DC power consumption
Solution Approach 1:
The patent applies dynamics by transitioning from fixed DC bias to dynamic bias control. The bias voltage is adjusted in real-time based on the input signal envelope amplitude, allowing the PA to adapt its operating point. This dynamic adjustment enables the system to achieve high linearity when needed while improving efficiency during other operating conditions.
Solution Approach 2:
The patent changes the bias parameter from a fixed value to a variable that depends on the signal envelope. By making the bias voltage a function of the input signal characteristics, the system can optimize both linearity and efficiency across different operating conditions, resolving the contradiction between these two parameters.
2Power
If input power is excessively increased to improve output power, then output power is improved, but linearity deteriorates due to gain reduction and signal distortion
Solution Approach 1:
The patent applies preliminary action by detecting the envelope amplitude of the input signal before amplification and using this information to pre-adjust the bias voltage and supply voltage. This proactive adjustment prevents the PA from entering non-linear regions, maintaining linearity even at high output power levels.
Solution Approach 2:
The system uses feedback by continuously monitoring the input signal envelope and adjusting the bias and supply voltages accordingly. This closed-loop control ensures that the PA operates within its linear region while maximizing output power, preventing gain reduction and signal distortion.
3Use of energy by moving object
If a non-linear switching PA (class-D, class-E, or class-F) is used to achieve high efficiency, then efficiency is improved, but linearity deteriorates making it unsuitable for linear modulation systems
Solution Approach 1:
The patent segments the operation into different modes based on the envelope amplitude. By dividing the operating range and applying different bias strategies for different segments, the system can achieve high efficiency in switching mode while maintaining linearity when required, thus resolving the contradiction between efficiency and linearity.
4Use of energy by moving object
If mode switching is implemented to operate in different operation modes according to different power regions, then efficiency is improved, but device complexity increases
Solution Approach 1:
The patent uses dynamic envelope detection to automatically determine the appropriate operating mode based on signal characteristics. This dynamic approach simplifies the control logic compared to complex mode switching mechanisms, as the system naturally transitions between operating regions based on the detected envelope amplitude, reducing overall device complexity while maintaining efficiency improvements.
Data Source
AI summary
A power amplifier system, a control method thereof, and a control device thereof are provided. The power amplifier system operates in a non-linear switching mode according to an envelope amplitude of an input signal under control of the control device. When the power amplifier is operated in the non-linear switching mode, a supply voltage and an input signal of the power amplifier are provided to the power amplifier by the control device according to pre-measured properties of the power amplifier so as to equip the power amplifier with a high power-added efficiency (PAE) and a better linearity.