Adaptive PA Predistortion Using Split Feedback Sideband Detection
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Solution Overview
Problem
Current power amplifiers in wireless communication systems face efficiency limitations due to the need to maintain low intermodulation distortion (IMD) levels, which increases costs and DC power consumption, especially for high-frequency signals, as high-speed components are required to process and cancel distortion.
Innovation Solution
An adaptive power amplifier linearization system that uses a linearizer with predistortion and a feedback block to generate a predistortion control signal, canceling high side and low side amplifier distortion, thereby reducing the need for high-speed components and lowering costs and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-speed components are used to process and cancel distortion in power amplifiers, then distortion cancellation performance is improved, but device complexity and power consumption increase
Solution Approach 1:
The feedback signal processing is segmented into two separate paths: one path processes the high sideband distortion and the other path processes the low sideband distortion. Each path uses dedicated downconversion and detection circuits operating at lower speeds, avoiding the need for a single high-speed processing path that would require complex and power-consuming high-speed components.
Solution Approach 2:
The high sideband and low sideband distortion components are extracted separately from the feedback signal using frequency-selective downconversion. By separating the distortion cancellation function into two independent lower-speed processing paths, the system eliminates the requirement for high-speed components while maintaining effective distortion cancellation performance.
2Manufacturing precision
If high-speed components are used to process and cancel distortion, then distortion cancellation performance is improved, but power consumption increases
Solution Approach 1:
The feedback signal processing is segmented into two separate paths: one path processes the high sideband distortion and the other path processes the low sideband distortion. Each path uses dedicated downconversion and detection circuits operating at lower speeds, avoiding the need for a single high-speed processing path that would require complex and power-consuming high-speed components.
Solution Approach 2:
The high sideband and low sideband distortion components are extracted separately from the feedback signal using frequency-selective downconversion. By separating the distortion cancellation function into two independent lower-speed processing paths, the system eliminates the requirement for high-speed components while maintaining effective distortion cancellation performance.
3Power
If power amplifier output power is increased, then system gain and link performance are improved, but intermodulation distortion increases
Solution Approach 1:
A feedback mechanism is implemented where a portion of the power amplifier output is fed back to a detection circuit that measures the high sideband and low sideband distortion. The measured distortion information is used to generate predistortion control signals that adjust the linearizer, creating a closed-loop system that actively compensates for intermodulation distortion even at high output power levels.
Solution Approach 2:
The linearizer applies predistortion to the input signal before amplification, pre-compensating for the expected nonlinearity of the power amplifier. This preliminary action, controlled by feedback from measured distortion, prevents intermodulation distortion from occurring in the first place, allowing high output power operation while maintaining low distortion.
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
The system improves power amplifier efficiency and linearity, reducing distortion and power consumption while maintaining regulatory compliance, thus enhancing the performance and cost-effectiveness of wireless communication systems.
Implementation Method 1
The linearizer may be configured to use a predistortion control signal to add predistortion to a receive signal to generate a predistorted signal
Implementation Method 2
The power amplifier may be configured to amplify power of the predistorted signal to generate a first amplified signal
Implementation Method 3
The feedback block may be configured to capture a feedback signal based on a previous amplified signal from the power amplifier, to determine high side and low side distortion of the captured feedback signal, and to generate the predistortion control signal based on the determined high side and low side distortion
Data Source
AI summary
An exemplary system comprises a linearizer, a power amplifier, and a feedback block. The linearizer may be configured to use a predistortion control signal to add predistortion to a receive signal to generate a predistorted signal. The power amplifier may be configured to amplify power of the predistorted signal to generate a first amplified signal. The power amplifier may also add high side and low side amplifier distortion to the predistorted signal. The high side and low side amplifier distortion may cancel at least a portion of the predistortion. The feedback block may be configured to capture a feedback signal based on a previous amplified signal from the power amplifier, to determine high side and low side distortion of the captured feedback signal, and to generate the predistortion control signal based on the determined high side and low side distortion.