Power Amplifier Bias Circuit Using Enable Shaping for Flat Gain
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Solution Overview
Problem
Existing RF power amplifier systems face challenges in managing gain variations, particularly when transitioning from a disabled to an enabled state, leading to inefficiencies and performance issues such as dynamic error vector magnitude (EVM) degradation.
Innovation Solution
A power amplifier system incorporating a bias block with a time-dependent signal generator and current amplifier to shape and amplify an enable signal, generating a correction current that adjusts the bias current to compensate for gain variations, using a resistor-capacitor (RC) network and current mirror configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a power amplifier is enabled to amplify RF signals, then the power amplifier provides signal amplification capability, but gain variation occurs during the transition from disabled to enabled state
Solution Approach 1:
The bias block generates a correction current in advance during the transition period when the power amplifier is enabled, before the gain variation fully occurs. This preliminary correction current adjusts the bias current to compensate for the upcoming gain variation, thereby maintaining stable gain throughout the transition from disabled to enabled state
2Stability of the object's composition
If the bias current is adjusted to compensate for gain variation, then gain stability is improved, but additional circuit components are required
Solution Approach 1:
The bias block is integrated with the power amplifier circuit, merging the gain compensation function into the existing power amplifier structure. The bias block uses the enable signal already present in the system and generates correction current that is directly applied to the biasing network, combining multiple functions into a unified circuit architecture rather than adding separate independent compensation systems
3Stability of the object's composition
If a time-dependent signal generator is used to shape the enable signal, then gain variation is corrected, but the circuit complexity increases
Solution Approach 1:
The bias block acts as an intermediary between the enable signal and the power amplifier biasing network. It shapes the enable signal to generate a correction current that compensates for gain variation, mediating the interaction between the control signal and the amplifier to achieve stable gain without requiring complex direct modification of the power amplifier circuit
Data Source
AI summary
Apparatus and methods for biasing a power amplifier are disclosed. In one embodiment, a method of biasing a power amplifier includes shaping an enable signal using a time-dependent signal generator to generate a control current, amplifying the control current using a current amplifier to generate a correction current, and generating a bias current for a power amplifier using a primary biasing circuit. The primary biasing circuit is configured to use the correction current to correct for a variation in gain of the power amplifier when the power amplifier is enabled.