Doherty Amplifier Mode Switching for Wideband Back-Off Efficiency
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Solution Overview
Problem
The existing Doherty amplifier fails to modulate impedance at the summing node effectively when the frequency of the input signal changes, leading to deteriorated amplification efficiency.
Innovation Solution
A Doherty amplifier that switches between in-phase and out-of-phase signal combinations based on frequency, switching between Doherty and outphasing operation modes to adjust impedance and maintain efficiency across varying frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional Doherty amplifier configuration is used with fixed phase shift elements, then the circuit structure is simple, but the impedance at the summing node cannot be modulated when frequency changes, leading to deteriorated amplification efficiency
Solution Approach 1:
The patent introduces dynamic phase shift elements that can adjust their phase shift amount according to frequency changes. The phase shift element includes switching elements that connect different capacitor combinations based on the operating frequency, enabling the impedance at the summing node to be modulated dynamically. This resolves the contradiction by transforming the static circuit structure into a dynamic one that adapts to frequency variations, maintaining amplification efficiency across different frequency ranges.
Solution Approach 2:
The patent changes the electrical parameters (phase shift amount, impedance) of the phase shift element based on frequency. By switching between different capacitor configurations, the phase shift amount and resulting impedance at the summing node are adjusted to match the optimal values for different frequency ranges. This parameter adaptation allows the amplifier to maintain high efficiency despite frequency variations, resolving the contradiction between simple structure and reliable performance.
2Reliability
If phase shift elements are added to match amplitude and phase between carrier and peak amplifiers, then amplification efficiency improves, but the impedance still cannot be modulated when frequency changes, limiting bandwidth
Solution Approach 1:
The patent makes the phase shift element dynamic by incorporating frequency-dependent switching mechanisms. The switching elements activate different capacitor configurations based on the input signal frequency, enabling the phase shift amount to vary dynamically. This dynamic adjustment allows the amplifier to maintain proper impedance matching and phase relationships across a wider frequency range, thereby expanding bandwidth while preserving amplification efficiency.
Solution Approach 2:
The phase shift element is designed to perform multiple functions: it provides the necessary phase shift for Doherty operation at the center frequency, and simultaneously adapts its phase shift amount for other frequency ranges through the switching mechanism. This multi-functionality allows a single circuit configuration to handle both efficiency matching and bandwidth expansion, resolving the contradiction between these two performance aspects.
3Stability of the object's composition
If the amplifier operates in a fixed mode (Doherty or outphasing), then the operation is stable, but it cannot adapt to frequency changes, deteriorating efficiency across different frequency ranges
Solution Approach 1:
The patent introduces a dynamic switching mechanism that automatically transitions between Doherty operation mode and outphasing operation mode based on the input frequency. The switching elements respond to frequency changes and reconfigure the circuit accordingly, maintaining stable operation within each frequency range while adapting to frequency variations. This dynamic mode switching resolves the contradiction by allowing the amplifier to preserve mode stability locally while achieving frequency adaptability globally.
Solution Approach 2:
The patent implements a frequency-dependent feedback mechanism where the operating mode is automatically selected based on the input frequency. The switching elements monitor the frequency and adjust the circuit configuration to maintain optimal operation. This feedback control ensures that the amplifier operates in the appropriate mode (Doherty or outphasing) for each frequency range, resolving the contradiction between mode stability and frequency adaptability.
Data Source
AI summary
A Doherty amplifier is configured to include a first transistor that amplifies a first signal and outputs the amplified first signal, a second transistor that amplifies a second signal and outputs the amplified second signal, and a combining circuit that combines the amplified first signal output from the first transistor and the amplified second signal output from the second transistor and outputs a combined signal of the amplified first signal and the amplified second signal, in which a signal mode in which the first signal amplified by the first transistor and the second signal amplified by the second transistor are combined in phase and a signal mode in which the first signal amplified by the first transistor and the second signal amplified by the second transistor are combined out of phase are switched in accordance with a frequency, and an operation mode is switched to a Doherty operation mode or an outphasing operation mode depending on the switched signal mode.