RF Power Amplifier Envelope Tracking at Low Output Power
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Solution Overview
Problem
Current wireless communication apparatuses, such as mobile phones, face challenges in reducing power consumption, especially at low power levels, as existing techniques like envelope tracking mode are not effective at these levels, leading to inefficiencies in high-frequency power amplifiers.
Innovation Solution
A wireless communication apparatus with a power amplifying circuit, a source voltage generating circuit, and a bias control circuit that switches between envelope tracking mode and variable control mode based on power levels, adjusting source voltage and bias in proportion to power levels to optimize power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If envelope tracking mode is used to improve power added efficiency at low power levels, then power consumption is reduced, but the complexity of the high-frequency signal processing apparatus increases due to additional circuits
Solution Approach 1:
The patent combines the envelope tracking function with the existing high-frequency signal processing circuits by integrating an envelope detection circuit into the amplitude modulated signal processing path. The envelope detection circuit extracts amplitude information from the amplitude modulated signal, and this envelope signal is used to control the power amplifier's operating point, thereby reducing power consumption without requiring completely separate additional circuits.
Solution Approach 2:
The power amplifier is designed to operate in multiple modes (linear mode and envelope tracking mode) depending on the output power level. The same power amplifier circuit serves both high power level operations with fixed source voltage and low power level operations with variable source voltage, making the apparatus multi-functional and reducing the need for separate dedicated circuits for each operating condition.
2Ease of operation
If fixed source voltage is used in linear mode, then the apparatus is simple to operate, but power added efficiency deteriorates at low power levels due to unnecessary DC power loss
Solution Approach 1:
The patent introduces dynamic control of the source voltage based on the output power level. When the output power level is low, the source voltage is varied in accordance with the envelope of the amplitude modulated signal, allowing the power amplifier to maintain optimal efficiency. This dynamic adjustment is controlled by the envelope detection circuit that extracts amplitude information from the input signal, enabling the system to adapt its operating characteristics to match the current power level requirements.
3Loss of energy
If envelope tracking mode is used to reduce DC power loss, then power added efficiency is improved, but the device complexity increases due to envelope detection and variable source voltage control circuits
Solution Approach 1:
The envelope detection circuit performs preliminary extraction of amplitude information from the amplitude modulated signal before the signal reaches the power amplifier. This pre-processing of the signal's envelope information allows the control circuit to prepare the appropriate source voltage level in advance, enabling the power amplifier to operate efficiently at low power levels without requiring complex real-time adjustment mechanisms during amplification.
Data Source
AI summary
A high-frequency signal processing apparatus and a wireless communication apparatus can achieve a decrease in power consumption. For example, when an indicated power level to a high-frequency power amplifier is equal to or greater than a second reference value, envelope tracking is performed by causing a source voltage control circuit to control a high-speed DCDC converter using a detection result of an envelope detecting circuit and causing a bias control circuit to indicate a fixed bias value. The source voltage control circuit and the bias control circuit indicate a source voltage and a bias value decreasing in proportion to a decrease in the indicated power level when the indicated power level is in a range of the second reference value to the first reference value, and indicate a fixed source voltage and a fixed bias value when the indicated power level is less than the first reference value.