Feed-Forward Linearizer Control for Power Amplifier ACPR
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Solution Overview
Problem
Power amplifiers suffer from non-linearity issues, such as intermodulation products and noise, which degrade their performance and increase power consumption, leading to reduced Adjacent Channel Power Ratio (ACPR) and increased power consumption.
Innovation Solution
A linearizer system that uses a feed-forward method with noise cancellers and a controller to adjust settings, sampling both input and output signals to cancel or reduce unwanted spectral components like intermodulation products and noise, thereby improving the linearity of the power amplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If power amplifier operates at high power, then output power is improved, but non-linearity increases causing degraded ACPR
Solution Approach 1:
The system segments the signal processing into multiple paths: a main signal path through the power amplifier and a separate cancellation path that processes a scaled version of the input signal. The cancellation path is further segmented into multiple cancellers that target different intermodulation products independently, allowing selective suppression without affecting the main output power.
Solution Approach 2:
The patent introduces cancellation signals as intermediary elements that mediate between the non-linear power amplifier output and the desired linear output. These cancellation signals are generated by processing the input signal through scaling factors and combining with the amplifier output to suppress intermodulation products, effectively acting as a mediator to correct non-linearity.
2Power
If power amplifier operates at high power, then output power is improved, but power consumption increases
Solution Approach 1:
The system employs feedback mechanisms where the output signal is monitored and fed back through the cancellation path. The controller adjusts scaling factors and canceller settings based on measured intermodulation products, creating a closed-loop system that optimizes power efficiency by reducing the need for excessive back-off operation while maintaining ACPR requirements.
3Object-generated harmful factors
If noise cancellers are added to improve linearity, then ACPR is improved, but device complexity increases
Solution Approach 1:
The patent implements dynamic control where the controller adjusts scaling factors and canceller activation based on operating conditions. Not all cancellers are always active; instead, the system dynamically enables only the necessary cancellers for current operating points, reducing effective complexity while maintaining linearity improvement when needed.
Solution Approach 2:
The system changes parameters such as scaling factors and canceller gain settings based on operating conditions rather than using fixed complex structures. By adjusting these parameters dynamically, the system achieves linearity improvement with simpler average complexity, as the full cancellation capability is only activated when intermodulation products exceed thresholds.
Data Source
AI summary
Linearizers can improve the linearity of power amplifiers by canceling or reducing amplitude of non-linearity components, (e.g., IM3, IM5, IM7, IM9, etc.) generated by the power amplifier. The linearizers can obtain samples of signals output by the power amplifier and process the samples to produce a canceling signal that is applied onto or into an output of the power amplifier. The canceling signal is generated such that when applied to the output of the power amplifier, the canceling signal cancels or reduces at least a portion of the non-linearity components produced by the power amplifier. A controller can improve the correction of the non-linearity components by executing one or more tuning algorithms and adjusting settings of the linearizer based on the results of the algorithm(s).