Switched-Mode Power Amplifier Impedance Compensation for Linearity
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Solution Overview
Problem
Power amplifiers in communication devices face challenges in achieving both linearity and high efficiency, as they often dissipate out-of-band frequency components, leading to power loss and non-linearities due to time-variant output impedance.
Innovation Solution
Incorporating impedance compensation circuitry that alters the output impedance of the power amplification stage based on a control signal, allowing out-of-band power to be stored in LC circuits instead of being dissipated, and using a switched mode power amplification stage to manage drive signals effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a band-pass filter is used to filter out-of-band frequency components, then frequency selectivity is improved, but power loss increases due to dissipation in dump resistor
Solution Approach 1:
The patent converts the harmful reflected power into a beneficial resource by storing it in LC circuits. The out-of-band frequency components that are reflected by the band-pass filter instead of being dissipated are captured and stored, transforming energy waste into usable energy storage that can be reused during active periods.
Solution Approach 2:
The patent implements a recovery mechanism for reflected power by using LC circuits to store the out-of-band frequency components during inactive periods. This allows the system to recover and reuse the energy that would otherwise be discarded, improving overall power efficiency while maintaining frequency selectivity.
2Device complexity
If out-of-band power is dissipated in dump resistor, then frequency filtering is simplified, but efficiency deteriorates due to power loss
Solution Approach 1:
The patent introduces dynamic switching between different operating modes using a control signal. The power amplification stage can switch between active and inactive states, and the LC circuits dynamically store or release energy based on the operational phase, optimizing efficiency without compromising filtering performance.
Solution Approach 2:
The patent employs periodic switching of the power amplification stage between active and inactive phases. During inactive periods, out-of-band power is stored in LC circuits; during active periods, the stored energy is utilized. This periodic operation maintains filtering effectiveness while significantly improving overall efficiency.
3Power
If power amplification stage operates continuously, then output power is maintained, but linearity deteriorates due to time-variant output impedance
Solution Approach 1:
The patent uses periodic switching of the power amplification stage between active and inactive states controlled by a control signal. This periodic operation allows the output impedance to be reset during inactive periods, preventing the accumulation of time-variant impedance effects and maintaining linearity while still delivering required output power during active phases.
Solution Approach 2:
The patent prepares the power amplification stage for optimal operation by resetting its state during inactive periods. The LC circuits pre-store energy and the amplifier is allowed to settle, ensuring that when the active phase begins, the amplifier operates from a known stable state, thereby maintaining linearity throughout the output cycle.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the efficiency and linearity of power amplifiers by reducing power loss and enabling fast response times, making them suitable for modern communication systems that require linear amplification.
Implementation Method 1
impedance compensation circuitry coupled to the output of the power amplification stage. The impedance compensation circuitry can selectively alter an output impedance of the power amplification stage as a function of a control signal
Implementation Method 2
allowing out-of-band power to be stored in LC circuits instead of being dissipated
Data Source
AI summary
One embodiment relates to a power amplifier that includes a switched mode power amplification stage. The power amplification stage has an output configured to provide an amplified output voltage as a function of a drive signal, where the drive signal fluctuates during a first time and is inactive during a second time. The power amplifier also includes impedance compensation circuitry coupled to the output of the power amplification stage. The impedance compensation circuitry can selectively alter an output impedance of the power amplification stage as a function of a control signal that is continuously de-asserted during the first time and continuously asserted during the second time. Other embodiments are also disclosed.