Multi-Stage RF Power Amplifier for Low Dynamic EVM
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Solution Overview
Problem
Radio frequency power amplifiers in wireless communication systems experience higher dynamic error vector magnitude (EVM) due to transient effects during Time Division Duplexing operations, which degrades signal linearity, especially at high data rates.
Innovation Solution
A radio frequency power amplifier circuit design that includes a first active device and a second active device in series, where the second device provides a lower supply voltage across the first device, and a bypass capacitor diverts RF signals, isolating the second device from the RF path, allowing for a fast transient response and low dynamic EVM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a radio frequency power amplifier is pulsed on and off during Time Division Duplexing operation, then the amplifier can support high data rate wireless communication systems, but transient effects cause dynamic error vector magnitude to increase and signal linearity to degrade
Solution Approach 1:
The power amplifier is divided into multiple stages: a first stage with an first active device that responds to enable signals for fast transient response, and a second stage with a second active device that provides power amplification. This segmentation allows the first stage to handle transient effects during pulsing while the second stage maintains signal linearity, thereby resolving the contradiction between high data rate support and signal linearity preservation
Solution Approach 2:
An intermediary circuit is introduced between the first and second active devices, including a bypass capacitor coupled to a node between the devices. This intermediary structure isolates the second active device from rapid voltage transients while allowing the first active device to respond quickly to enable signals, thus maintaining both fast transient response and low dynamic EVM
2Manufacturing precision
If the power amplifier responds quickly to enable signals for fast transient response, then dynamic EVM can be reduced, but circuit complexity increases
Solution Approach 1:
The amplifier circuit is segmented into two functional stages with distinct roles: the first active device stage handles transient response to enable signals, while the second active device stage handles power amplification. This functional segmentation achieves low dynamic EVM through differentiated design responsibilities, preventing the need for over-engineering a single complex stage
Solution Approach 2:
Different parts of the circuit are designed with different properties optimized for their specific functions. The first active device is optimized for fast transient response to enable signals, while the second active device is optimized for power amplification and linearity. The bypass capacitor is strategically placed to provide local voltage stabilization. This local optimization achieves low dynamic EVM without requiring all circuit elements to be complex
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 design achieves a low dynamic EVM of about 3 percent or less, improving signal linearity and maintaining performance even at high data rates and high main supply voltages.
Implementation Method 1
A bypass capacitor may be coupled with a node between the first active device and the second active device to divert RF signals at the node
Data Source
AI summary
Embodiments provide a multi-stage radio frequency (RF) power amplifier (PA) having a low dynamic error vector magnitude (EVM). A first stage of the RF PA may include a first active device configured to receive an enable signal and to turn on in response to the enable signal, thereby activating the first stage. The RF PA may further include a second active device coupled in series with the first active device and configured to receive a main supply voltage. The second active device may provide a first supply voltage across the first active device that is less than and independent of the main supply voltage. One of the first active device or the second active device may be configured to receive an RF input signal and to pass an amplified RF output signal to a second stage of the RF PA circuit.