Cascode Power Amplifier Bias Switching for Envelope Tracking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing amplification circuits using envelope tracking (ET) suffer from deteriorated amplification characteristics due to capacitance components in the wiring that supply power supply voltages, leading to inefficiencies and reduced gain.
Innovation Solution
The amplification circuit employs a configuration with cascode-connected power amplifiers and a switching circuit that maintains constant direct-current power supply voltages to each amplifier, while using digital control signals to switch bias currents based on envelope signals, thereby suppressing waveform blunting and maintaining efficiency and gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If power supply voltages are supplied from the tracker circuit to the amplification circuit using wiring, then the amplification circuit can operate with envelope tracking, but the capacitance components of the wiring cause waveform blunting and deteriorate amplification characteristics
Solution Approach 1:
The patent divides the amplification circuit into multiple independent power amplifier units (first power amplifier and second power amplifier), each with its own constant power supply voltage. This segmentation eliminates the need for high-speed switching of power supply voltages, thereby preventing waveform blunting caused by wiring capacitance while maintaining amplification efficiency.
Solution Approach 2:
The patent applies equipotentiality by providing constant power supply voltages (first power supply voltage and second power supply voltage at different voltage levels) to each power amplifier unit without switching. This eliminates voltage transitions and associated waveform blunting, while the biasing circuit enables efficient operation across different power levels.
2Loss of energy
If power supply voltage switching is performed based on envelope signals, then power added efficiency can be improved, but gain and amplification characteristics deteriorate due to wiring capacitance
Solution Approach 1:
The patent segments the power amplification function into multiple parallel power amplifier units that can be independently controlled. Each unit operates with a constant power supply voltage, eliminating waveform blunting. The biasing circuit selectively activates specific units based on envelope signal levels, achieving high power added efficiency without compromising amplification gain.
Solution Approach 2:
The patent introduces dynamics through the biasing circuit, which dynamically adjusts the operating state of each power amplifier unit based on the envelope signal. While power supply voltages remain constant to avoid waveform blunting, the bias currents are dynamically controlled to optimize efficiency and maintain gain across varying signal conditions.
3Productivity
If multiple discrete voltage levels are supplied to the amplification circuit, then power efficiency is improved, but device complexity increases
Solution Approach 1:
The patent uses segmentation to provide multiple voltage levels by creating separate power supply paths for different voltage levels (first power supply voltage and second power supply voltage). Each power amplifier unit is connected to a specific voltage level, simplifying the overall circuit architecture compared to complex switching networks while maintaining power efficiency.
Solution Approach 2:
The biasing circuit serves multiple functions: it provides bias currents to multiple power amplifier units, selectively activates units based on envelope signal levels, and enables efficient operation across different power levels. This multi-functionality reduces the need for additional complex control circuitry.
Data Source
AI summary
An amplification circuit includes a power supply voltage terminal that receives a power supply voltage V1, a power supply voltage terminal that receives a power supply voltage V2 having a different voltage level from that of the power supply voltage V1, digital control terminals that receive digital control signals based on an envelope signal, a power amplifier connected to the power supply voltage terminal, a power amplifier connected to the power supply voltage terminal, a synthetic circuit connected to the power amplifiers, a biasing circuit that supplies bias currents, and a switching circuit connected to the digital control terminals and configured to switch connection and disconnection between the biasing circuit and the power amplifier and to switch connection and disconnection between the biasing circuit and the power amplifier. Each of the power amplifiers includes multiple cascode-connected amplification transistors.