Cross-Coupled Power Amplifier Circuit for Smooth Envelope Tracking
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Solution Overview
Problem
In power amplifier circuits for wireless communication devices, especially in 5G systems, the high modulation bandwidth makes it difficult for digital envelope tracking systems to smoothly control the power-supply voltage, leading to stepped changes in voltage, which results in discrete gain levels and non-linear amplification due to the power-supply voltage dependence of transistor gain.
Innovation Solution
A power amplifier circuit design that includes transistors with collector-base capacitance and cross-coupling capacitance circuits to reduce the power-supply voltage dependence of gain, allowing for continuous amplification by compensating voltage changes and reducing gain variations, thereby enabling smooth envelope tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If digital envelope tracking is used to control power-supply voltage, then power efficiency is improved, but the voltage changes in a stepped manner causing discrete gain levels and non-linear amplification
Solution Approach 1:
The patent introduces a feedback mechanism where the output signal is fed back to the power-supply voltage control circuit. This feedback loop acts as an intermediary that continuously adjusts the power-supply voltage based on the actual output, transforming the discrete stepped control into effective continuous voltage adjustment, thereby maintaining amplification linearity while preserving power efficiency benefits
Solution Approach 2:
The patent implements a feedback system where the output signal is monitored and used to adjust the power-supply voltage in real-time. This feedback mechanism compensates for the discrete nature of digital envelope tracking by dynamically adjusting voltage levels to maintain continuous gain, resolving the contradiction between digital control efficiency and analog-like smooth amplification
2Productivity
If the modulation bandwidth is increased for 5G systems, then communication capacity is improved, but the envelope tracker cannot reach the signal speed
Solution Approach 1:
The feedback mechanism allows the envelope tracker to respond to actual output conditions rather than relying solely on high-speed direct control. By continuously monitoring and adjusting based on feedback, the system can effectively handle high modulation bandwidths even with limited direct control speed, enabling 5G communication capacity requirements to be met
3Reliability
If stepped signal is generated with longer period to match envelope signal, then envelope tracking is achieved, but the gain changes in stepped manner and amplification is not smooth
Solution Approach 1:
The feedback loop continuously monitors the output and adjusts the power-supply voltage to compensate for stepped changes. This creates an effective smooth amplification response even though the underlying control signal remains stepped, resolving the contradiction between envelope tracking accuracy and amplification smoothness
Solution Approach 2:
The patent dynamically changes the power-supply voltage parameter based on feedback from the output signal. This dynamic parameter adjustment transforms the fixed stepped voltage levels into effectively continuous voltage levels, maintaining both envelope tracking accuracy and amplification smoothness
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 solution effectively reduces the power-supply voltage dependence of gain, allowing for continuous amplification and preventing harmonic components from modulating into the high-frequency signal, thus enhancing linearity and reducing non-linearity, even with stepped changes in power-supply voltage.
Implementation Method 1
a first capacitance circuit electrically connected between the collector of the second transistor and the base of the first transistor; and a second capacitance circuit electrically connected between the collector of the first transistor and the base of the second transistor
Data Source
AI summary
A power amplifier circuit includes a first transistor having an emitter electrically connected to a common potential, a base to which a first high-frequency signal is input, and a collector from which a third high-frequency signal is output; a second transistor having an emitter electrically connected to the common potential, a base to which a second high-frequency signal is input, and a collector from which a fourth high-frequency signal is output; a first capacitance circuit electrically connected between the collector of the second transistor and the base of the first transistor; and a second capacitance circuit electrically connected between the collector of the first transistor and the base of the second transistor.