Power Amplifier Bias Circuit for Flat Gain During Enable
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Solution Overview
Problem
Existing power amplifier systems face challenges in managing RF signal amplification, leading to potential out-of-band transmission and inefficient biasing, which affects the gain stability and performance, particularly in mobile devices.
Innovation Solution
A power amplifier system with a bias block that includes a time-dependent signal generator, current amplifier, and primary biasing circuit to shape and amplify the enable signal, generating a correction current to adjust the bias current and compensate for gain variations, ensuring stable gain over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a power amplifier is used to amplify RF signal, then the power of RF signal is boosted, but the gain of power amplifier varies when it is enabled, causing out-of-band transmission
Solution Approach 1:
The patent applies preliminary action by generating a correction current before the power amplifier is fully enabled. The time-dependent signal generator creates a preliminary current that anticipates the gain variation, and this correction current is injected into the biasing circuit to pre-compensate for the expected gain change, thereby maintaining stable gain from the moment the amplifier is enabled.
Solution Approach 2:
The patent implements feedback by continuously monitoring the enable signal of the power amplifier and using it to generate a correction current that counteracts gain variations. The biasing circuit receives feedback about the amplifier's operational state and adjusts the bias current accordingly, creating a closed-loop system that maintains gain stability despite dynamic operating conditions.
2Speed
If the enable signal is directly applied to the power amplifier, then the amplifier is quickly enabled, but the gain varies during the transition, affecting transmission accuracy
Solution Approach 1:
The patent introduces an intermediary element - the time-dependent signal generator and correction current circuit - that mediates between the enable signal and the power amplifier. Instead of directly applying the enable signal to the amplifier, the system uses this intermediary to shape the enabling process and generate appropriate correction currents that maintain gain accuracy during the transition.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the bias current parameters based on the enable signal timing. The system changes the current magnitude and timing parameters of the correction current to match the specific moment in the enable transition, allowing fast enabling while maintaining accurate gain control through parameter optimization.
3Device complexity
If conventional biasing circuit is used, then the circuit is simple, but it cannot compensate for gain variations, leading to poor transmission performance
Solution Approach 1:
The patent applies segmentation by dividing the biasing function into separate components: a conventional biasing circuit for basic operation and an additional correction current generation circuit for gain stabilization. This segmentation allows the system to maintain the simplicity of conventional biasing while adding targeted functionality to compensate for gain variations, improving transmission performance without completely redesigning the biasing system.
Data Source
AI summary
Apparatus and methods for biasing of power amplifiers are disclosed. In one embodiment, a mobile device includes a transceiver that generates a radio frequency signal and a power amplifier enable signal, a power amplifier that provides amplification to the radio frequency signal and that is biased by a bias signal, and a bias circuit that receives the power amplifier enable signal and generates the bias signal. The bias circuit includes a gain correction circuit that generates a correction current in response to activation of the power amplifier enable signal, and a primary biasing circuit that generates the bias signal based on the correction current and the power amplifier enable signal.