Power Amplifier Linearization with Echo Cancellation Feedback
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Solution Overview
Problem
Power amplifiers in transmitters are non-linear, leading to distortion and out-of-band emission that reduce signal-to-noise ratio (SNR), and conventional methods for reducing distortion require accurate analog-to-digital converters, increasing complexity and cost.
Innovation Solution
A system combining power amplifier linearization and non-linear echo cancellation, where a portion of the transmit signal is tapped off for feedback, allowing for digital domain processing to reduce the dynamic range requirements of the ADC and implement a smaller, less power-consuming ADC, while also using an echo canceller to remove residual non-linear echoes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to reduce non-linear distortion, then distortion is reduced, but a very accurate ADC is required which increases complexity and cost
Solution Approach 1:
The patent segments the echo cancellation task into two parts: a linear echo canceller that handles the linear component of the echo, and a non-linear echo canceller that handles the remaining non-linear component. This segmentation allows the system to reduce distortion while using a less accurate ADC, thereby reducing complexity and cost.
Solution Approach 2:
The patent introduces a linear echo canceller as an intermediary component that processes the feedback signal before it is fed to the non-linear echo canceller. This intermediary linear processing simplifies the requirements for the ADC by removing the linear component of the echo, allowing the use of a less accurate ADC while still achieving good distortion reduction.
2Manufacturing precision
If a very accurate ADC is used to estimate the signal after power amplification, then distortion is reduced, but system complexity and cost increase
Solution Approach 1:
The patent segments the echo cancellation task into two parts: a linear echo canceller that handles the linear component of the echo, and a non-linear echo canceller that handles the remaining non-linear component. This segmentation allows the system to reduce distortion while using a less accurate ADC, thereby reducing complexity and cost.
3Manufacturing precision
If power amplifier operates in linear region, then distortion is reduced, but power efficiency decreases
Solution Approach 1:
The patent applies preliminary digital predistortion to the transmit signal before it is amplified by the power amplifier. This predistortion pre-compensates for the non-linearities of the power amplifier, allowing the amplifier to operate in a more efficient region while still achieving good linearity in the final output signal.
Solution Approach 2:
The patent implements a feedback path that taps a portion of the transmit signal and feeds it back through a linear echo canceller and non-linear echo canceller. This feedback mechanism allows the system to continuously monitor and correct for non-linear distortions, enabling the power amplifier to operate efficiently while maintaining signal quality.
Data Source
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AI summary
A system for power amplifier linearization comprises a power amplifier configured to amplify a transmit signal; a digital-to-analog converter configured to convert the transmit signal to an analog domain; a coupler for coupling the transmit signal after amplifying by the power amplifier to a transmit port; a signal cancelation system for canceling a linear component of the transmit signal from the feedback signal in an analog domain; an analog-to-digital converter for converting the feedback signal after canceling the linear component of the transmit signal to a digital domain; an echo cancelation filter for generating an echo cancelation signal either from the feedback signal after canceling the linear component of the transmit; and a subtractor for subtracting the echo cancelation signal from the receive signal in a digital domain.