Power Supply Modulation for Doherty Amplifier Efficiency
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Solution Overview
Problem
Conventional Doherty amplifiers cannot detect load modulation, leading to efficiency decreases when signal levels are low, and power supply modulation units fail to adjust back-off levels correctly, resulting in inefficiencies.
Innovation Solution
A power supply modulation device that detects amplitudes from digital signals, calculates time differential values of amplitude ratios, and controls power supply voltages to determine and adjust for changes in output impedance of the combining circuit, ensuring efficient operation even when load modulation does not occur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional Doherty amplifier operation is used, then high efficiency operation is achieved when load modulation occurs, but efficiency decreases when signal levels are low and load modulation does not occur
Solution Approach 1:
The patent implements dynamic switching between two operational modes (first operation mode and second operation mode) based on detected load modulation conditions. The operation mode switching unit dynamically selects the appropriate mode to maintain high efficiency across different signal levels, making the system adaptable to varying operating conditions rather than being fixed in a single mode.
Solution Approach 2:
The patent employs a detection unit that continuously monitors load modulation conditions by calculating time differential values of amplitude ratios. This feedback mechanism provides real-time information about the operating state, enabling the operation mode switching unit to make informed decisions about mode selection to optimize efficiency under different signal level conditions.
2Extent of automation
If power supply modulation unit is applied to conventional Doherty amplifier, then power supply modulation is performed, but back-off level detection fails when carrier amplifier and peaking amplifier are switched
Solution Approach 1:
The patent introduces an operation mode switching unit as an intermediary between the detection unit and power supply modulation unit. This intermediary component ensures that power supply modulation is only performed when load modulation is detected, preventing incorrect back-off level detection and modulation when the amplifier configuration has switched, thereby maintaining measurement precision while preserving automation capability.
3Adaptability or versatility
If carrier amplifier and peaking amplifier are switched based on signal power, then amplifier flexibility is improved, but load modulation detection becomes unreliable
Solution Approach 1:
The patent performs preliminary detection of load modulation conditions through calculating time differential values of amplitude ratios before making amplifier switching decisions or power supply modulation adjustments. This preliminary action ensures that the detection of load modulation is performed under known operating conditions, maintaining reliability even when amplifier configurations are switched.
Data Source
AI summary
A power supply modulation device includes a unit detecting, from a first digital signal, a first amplitude being the amplitude of a first analog signal provided to a first amplifier and detecting, from a second digital signal, a second amplitude being the amplitude of a second analog signal provided to a second amplifier; a unit that calculates a time differential value of a ratio of the first amplitude to a sum of the first amplitude and the second amplitude, and determines, on the basis of the time differential value, whether or not output impedance of a combining circuit that combines together the first analog signal amplified and the second analog signal changes along with a change in power of the combined signal; and a unit that controls a power supply voltage supplied to each of the first amplifier and the second amplifier, on the basis of the determination.