Envelope-Tracking Power Amplifier Bias Regulation for Low Gain Variation
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Solution Overview
Problem
Power amplifier circuits face challenges in maintaining low gain variation and high power efficiency, especially when dealing with wide modulation bandwidth transmission signals, as existing envelope tracking systems struggle to generate a power supply voltage that completely follows the signal envelope, leading to varying power supply voltage levels and subsequent gain variations.
Innovation Solution
A power amplifier circuit design that includes a regulation circuit to adjust bias currents based on changes in power supply voltage, using a combination of transistors, capacitors, and inductors to regulate the bias current and reduce gain dependence on power supply voltage, thereby minimizing gain variation while maintaining high power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a power supply voltage is changed to follow the envelope of a transmission signal in an ET system, then power efficiency is improved, but gain variation increases when the modulation band width is wide (100 MHz or more) because the power supply voltage cannot completely follow the envelope
Solution Approach 1:
The patent employs feedback mechanisms where the power supply voltage adjustment is continuously monitored and corrected based on the actual envelope tracking performance. The system detects deviations between the desired and actual power supply voltage levels and adjusts the bias current accordingly to maintain consistent gain while preserving power efficiency benefits
Solution Approach 2:
The patent dynamically adjusts multiple parameters including power supply voltage, bias current, and amplifier operating point in response to modulation bandwidth conditions. By changing these parameters adaptively, the system maintains optimal performance across different operating conditions, reducing gain variation while preserving power efficiency improvements
2Adaptability or versatility
If the power supply voltage changes at a slower rate to be applicable to wide modulation bandwidth signals, then adaptability to wide bandwidth signals is improved, but gain variation increases due to different power supply voltage levels for the same output power
Solution Approach 1:
The patent implements dynamic adjustment mechanisms that allow the power supply voltage and bias current to adapt in real-time to modulation bandwidth variations. The system transitions from static to dynamic operation, continuously optimizing the power supply voltage waveform to maintain both adaptability to wide bandwidth signals and consistent gain performance
Solution Approach 2:
The system uses feedback loops to monitor the relationship between power supply voltage levels and output power, automatically correcting gain variations by adjusting the bias current based on detected deviations, thereby maintaining consistent amplification across different modulation bandwidth conditions
3Use of energy by moving object
If envelope tracking is applied to transmission signals with 100 MHz or more modulation band width, then power efficiency can be maintained, but it becomes difficult to generate a power supply voltage that completely follows the envelope
Solution Approach 1:
The patent introduces intermediate processing stages and circuit elements that facilitate the generation of power supply voltage waveforms suitable for wide bandwidth signals. These intermediary components bridge the gap between the ideal envelope tracking requirement and the practical limitations of generating high-frequency power supply voltages, maintaining power efficiency while simplifying the generation process
Data Source
AI summary
A power amplifier circuit includes an amplifier transistor having a first terminal supplied with a power supply voltage that changes in accordance with an amplitude level of an input signal, and a second terminal supplied with the input signal and a bias current, an amplified signal obtained by amplifying the input signal being outputted from the first terminal, a bias circuit that outputs the bias current from an output terminal thereof in accordance with a reference current supplied to an input terminal thereof, and a regulation circuit that generates a regulation current for regulating the bias current in accordance with a change in the power supply voltage. The regulation current increases with an increase in the power supply voltage, and decreases with a decrease in the power supply voltage. The regulation circuit extracts the regulation current from at least one of the reference current or the bias current.