Hybrid Bias Compensation for RF Power Amplifier Drift Control
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Solution Overview
Problem
Current transmitter systems with gallium nitride (GaN) RF power amplifiers face challenges in mitigating charge trapping and drift due to latency between the baseband controller and power amplifier module, making real-time compensation impractical.
Innovation Solution
A transmitter system with hybrid digital drift/trap compensation, incorporating a baseband processor, RF power amplifier, and bias processor that generates feedback envelope error signals to correct dynamic bias errors through analog bias adjustments, using converters and digital pre-distortion to mitigate amplification variations and nonlinearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If baseband controller is used to control RF power amplifier, then control functions can be implemented, but latency occurs between baseband controller and power amplifier module making real-time compensation impractical
Solution Approach 1:
The control system is divided into two independent parts: a baseband processor for non-time-critical functions and a dedicated bias processor for real-time bias control. This segmentation allows the bias processor to operate independently with direct access to the power amplifier, eliminating the latency bottleneck while the baseband processor handles higher-level control functions.
Solution Approach 2:
A bias processor is introduced as an intermediary component between the baseband processor and the power amplifier. This intermediary handles the time-critical bias control functions, receiving commands from the baseband processor and directly adjusting the power amplifier bias without waiting for baseband processing cycles, thus reducing latency.
2Ease of manufacture
If one-time programmable codeplug is used for power amplifier control, then settings can be stored, but all characterization must be accomplished during manufacturing process
Solution Approach 1:
The bias control system transitions from a static, one-time programmable configuration to a dynamic system where the bias processor can continuously adjust bias settings in real-time based on operating conditions. This allows the power amplifier to adapt to varying requirements after manufacturing, enhancing versatility while maintaining the simplicity of pre-wired control for basic functions.
Data Source
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AI summary
The present disclosure relates to a transmitter system that includes an RF power amplifier (PA) and a baseband processor (14). The RF PA is configured to amplify an RF input signal to an RF output signal and configured to receive an analog bias adjustment signal, which is applied to correct dynamic bias errors in the RF PA caused by amplification variations that have time constants. The baseband processor (14), in response to an input envelope and a feedback output envelope, is configured to generate a feedback envelope error signal. Herein, the input envelope is estimated based on a baseband input signal received by the baseband processor (14), and the feedback output envelope is estimated based on the RF output signal. The RF input signal and the analog bias adjustment signal fed to the RF PA are generated from the baseband input signal and the feedback envelope error signal, respectively.