Power Amplifier Linearization Using Analog Echo Cancellation
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Solution Overview
Problem
Power amplifiers in transmitters are non-linear, leading to distortion and out-of-band emission, which reduces the signal-to-noise ratio (SNR) of both transmit and receive signals, and existing methods require accurate analog-to-digital converters (ADCs) for linearization, increasing complexity and cost.
Innovation Solution
A system combining power amplifier linearization with non-linear echo cancellation, where the linear component of the transmit signal is subtracted from the feedback signal to increase the ADC's dynamic range, allowing for a smaller and less power-consuming ADC, and the remaining non-linear echo is cancelled in the digital domain using a linear filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional power amplifier linearization methods are used, then the power amplifier's power back-off is reduced and power efficiency is increased, but a very accurate analog-to-digital converter (ADC) is required to estimate the signal after power amplification, increasing system complexity and cost
Solution Approach 1:
The patent extracts and removes the linear component of the power amplifier output signal before it enters the ADC. By separating the linear component (which consumes most of the signal energy) from the non-linear distortion components, the system can use a lower-resolution ADC while still achieving accurate linearization. This is accomplished through a feedback path that processes the amplified signal and subtracts the linear portion, leaving only the distortion components for digital processing.
Solution Approach 2:
The patent changes the parameter being measured by the ADC from the full power amplifier output signal to only the non-linear distortion components. This parameter transformation allows the use of a lower-resolution ADC (reducing complexity and power consumption) while maintaining the ability to accurately estimate and compensate for power amplifier non-linearities through digital signal processing.
2Measurement precision
If a high-resolution ADC is used for power amplifier linearization, then accurate signal estimation is achieved, but the ADC consumes more power and occupies more area
Solution Approach 1:
The patent removes the dominant linear component from the feedback signal path, leaving only the non-linear distortion components to be processed by the ADC. This extraction enables the use of a lower-resolution, lower-power ADC while maintaining sufficient measurement precision for linearization purposes, as the ADC only needs to resolve the smaller distortion components rather than the full dynamic range of the amplified signal.
3Loss of information
If the linear component of the power amplifier output signal is included in the feedback signal to the ADC, then complete signal information is available, but the ADC dynamic range requirement increases significantly
Solution Approach 1:
The patent extracts and eliminates the linear component from the feedback signal path using a subtraction mechanism. This allows the ADC to process only the non-linear distortion components with reduced dynamic range requirements, while the linear component is handled separately through the predistortion system, maintaining overall signal information completeness without overwhelming the ADC.
Solution Approach 2:
The patent segments the power amplifier output signal into two distinct components: the linear component and the non-linear distortion components. The linear component is processed through a separate feedback path, while the distortion components are fed to the ADC for digital processing. This segmentation allows each component to be handled by the most appropriate processing mechanism, reducing the ADC's dynamic range burden.
Data Source
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AI summary
A system and method for power amplifier linearization with echo cancelation capabilities. The system includes a power amplifier configured to amplify a transmit signal and a linearization device configured distort the transmit signal in a digital domain to linearize a transfer function of the power amplifier. A signal cancelation system is included for canceling a linear component of the transmit signal from the feedback signal in an analog domain. A signal reconstruction filter reconstructs the linear component of the transmit signal in a digital domain, and the reconstructed linear component of the transmit signal is combined with the feedback signal after canceling the linear component of the transmit signal in an analog domain. The parameters for the linearization device are generated based on an output of the combination.