Input Impedance Control in Power Amplifiers for AM-PM Suppression
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Solution Overview
Problem
Power amplifiers in mobile communications terminals face limitations in increasing battery life due to size constraints, and existing power amplifiers struggle to maintain linearity characteristics while suppressing both amplitude and phase fluctuations in output signals, particularly phase fluctuations (AM-PM) caused by input level changes.
Innovation Solution
A power amplifier design that varies impedance between the signal input terminal and the amplification unit based on the power level of the input signal, using a bias voltage generation unit, an amplification unit, and an impedance variation unit with a transistor and inductor to adjust impedance in accordance with the bias voltage, thereby suppressing phase fluctuations in the output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a power amplifier is designed to satisfy linearity characteristics at maximum output level, then linearity is improved, but power consumption increases
Solution Approach 1:
The patent applies dynamics by making the impedance of the signal transmission path adjustable rather than fixed. The impedance variation unit changes the impedance according to the power level of the input signal, allowing the system to adapt its characteristics dynamically. This enables the power amplifier to maintain linearity characteristics across different operating conditions without continuously operating at maximum power level, thus resolving the contradiction between linearity and power consumption.
Solution Approach 2:
The patent changes the impedance parameter of the signal transmission path based on the input signal power level. By varying this parameter dynamically, the system can optimize its performance for different operating conditions. When the input signal is at maximum level, the impedance is adjusted to ensure linearity; when the input signal is lower, the impedance changes to reduce power consumption while maintaining acceptable linearity, thus resolving the contradiction.
2Manufacturing precision
If a method suppresses fluctuations in the level (AM-AM) of output signals, then amplitude linearity is improved, but phase fluctuations (AM-PM) occur in accordance with input level fluctuations
Solution Approach 1:
The patent introduces an intermediary mechanism - the impedance variation unit - that mediates between the input signal and the amplification unit. This intermediary dynamically adjusts the impedance of the signal transmission path based on the input signal power level, which simultaneously addresses both amplitude linearity and phase stability. The impedance adjustment acts as a compensating mechanism that prevents phase fluctuations caused by AM-PM effects while maintaining amplitude linearity.
3Duration of action of moving object
If battery size is increased to extend mobile terminal usage period, then usage period is improved, but terminal weight and size increase
Solution Approach 1:
The patent employs periodic or conditional action by adjusting the impedance based on the power level of the input signal. Rather than operating continuously at high power, the system dynamically adapts its impedance to match the actual signal conditions. This allows the power amplifier to consume less power during normal operation while maintaining performance when needed, effectively extending battery life without increasing battery size, weight, or terminal dimensions.
Data Source
AI summary
There is provided a power amplifier which may suppress fluctuations in a phase of an output signal in accordance with fluctuations in a level of an input signal by varying an impedance between a signal input terminal and an amplification unit in accordance with a power level of an input signal. The power amplifier includes a bias voltage generation unit generating a bias voltage set in accordance with a power level of an input signal, an amplification unit amplifying the power level of the input signal in accordance with the bias voltage, and an impedance variation unit varying an impedance of a signal transmission path through which the input signal is transmitted to the amplification unit in accordance with the bias voltage.