Envelope Tracking PA Supply Control for Lower Spectral Noise
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Solution Overview
Problem
RF power amplifiers in portable devices face challenges in maintaining uniform gain while minimizing spectral noise, as conventional envelope tracking methods can introduce non-monotonic variations in supply voltage, leading to increased spectral noise.
Innovation Solution
The RF power amplifier system adjusts the supply voltage in a monotonic manner relative to the amplitude of the RF input signal, ensuring the voltage either increases or remains constant, which may cause some gain variations but reduces overall spectral noise by minimizing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the supply voltage is adjusted to maintain uniform gain in the PA, then the gain uniformity is improved, but non-monotonic variations in supply voltage increase spectral noise
Solution Approach 1:
The patent changes the parameter of supply voltage adjustment from non-monotonic to monotonic variation. Instead of adjusting voltage to perfectly maintain uniform gain, the system accepts some gain variation in exchange for monotonic voltage changes, thereby reducing spectral noise while maintaining acceptable performance
Solution Approach 2:
The patent converts the harmful non-monotonic voltage variations into beneficial monotonic variations. By intentionally allowing gain to vary rather than forcing uniform gain, the system transforms what would be a stability problem into a solution that reduces spectral noise through monotonic voltage behavior
2Object-generated harmful factors
If the supply voltage is adjusted monotonically to reduce spectral noise, then spectral noise is reduced, but gain uniformity deteriorates
Solution Approach 1:
The system changes the voltage adjustment parameter from non-monotonic to monotonic, accepting the trade-off of some gain variation to achieve the benefit of reduced spectral noise through monotonic voltage behavior
Data Source
AI summary
A radio frequency (RF) power amplifier system that comprises a power amplifier configured to amplify an RF input signal to generate an RF output signal. The power amplifier has a gain that is controlled by a supply voltage to the power amplifier. An amplitude detector is configured to generate an amplitude signal indicative of an amplitude of the RF input signal. A power supply generates the supply voltage to the power amplifier based on the amplitude signal indicative of the amplitude of the RF input signal. The gain of the power amplifier is allowed to have variations over the amplitude range of the RF input signal in favor of having a supply voltage that is monotonic relative to the amplitude of the RF input signal across an amplitude range of the RF input signal.