Doherty Amplifier Phase Switching for Summing-Node Impedance Modulation
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Solution Overview
Problem
In Doherty amplifiers, the impedance at the summing node cannot be modulated when the frequency of the input signal changes, leading to deteriorated amplification efficiency.
Innovation Solution
The Doherty amplifier switches between in-phase and out-of-phase signal combinations based on frequency, switching between Doherty and outphasing operation modes to modulate 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 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 applies dynamics by making the phase shift amount variable rather than fixed. The phase shift element's phase shift amount changes dynamically according to the frequency of the input signal, allowing the impedance at the summing node to be modulated adaptively. This resolves the contradiction by introducing frequency-dependent phase adjustment that maintains amplification efficiency across varying frequencies while keeping the overall structure relatively simple.
Solution Approach 2:
The patent changes the parameter of phase shift amount based on frequency. By adjusting the phase shift amount parameter in response to frequency changes, the impedance modulation capability is achieved. This parameter change approach allows the amplifier to adapt to different operating conditions, maintaining efficiency without requiring a completely complex reconfiguration of the amplifier structure.
2Manufacturing precision
If phase adjusters are added to match amplitude and phase between carrier and peak amplifiers, then amplitude and phase matching is improved, but the impedance at the summing node still cannot be modulated when frequency changes
Solution Approach 1:
The patent makes the phase shift element dynamic by configuring it to change its phase shift amount according to the frequency of the input signal. This dynamic behavior enables the system to adapt to frequency changes while maintaining amplitude and phase matching between the carrier and peak amplifiers, thus resolving the contradiction between matching precision and frequency adaptability.
Solution Approach 2:
The phase shift element serves multiple functions: it maintains amplitude and phase matching between amplifiers while simultaneously providing frequency-dependent impedance modulation at the summing node. This multi-functionality allows a single element to address both matching precision and frequency adaptability requirements.
3Ease of operation
If the amplifier operates in a single mode, then the operation is simple, but the bandwidth of efficiency characteristics cannot be widened when signal frequencies change
Solution Approach 1:
The patent implements dynamic switching between Doherty operation mode and outphasing operation mode based on the frequency of the input signal. This dynamic mode selection allows the amplifier to maintain optimal efficiency across a wider bandwidth by adapting to frequency changes, while keeping the control logic relatively simple through frequency-based decision-making.
Solution Approach 2:
The patent changes the operation mode parameter (Doherty or outphasing) according to frequency. By switching between modes based on frequency thresholds, the system achieves wider efficiency bandwidth without complex continuous adjustment mechanisms, maintaining operational simplicity while improving adaptability.
Data Source
Figure 1~2
Figure 3
Figure 4A~4C
AI summary
A Doherty amplifier (1) is configured to include a first transistor (16) that amplifies a first signal and outputs the amplified first signal, a second transistor (20) that amplifies a second signal and outputs the amplified second signal, and a combining circuit (31) that combines the amplified first signal output from the first transistor (16) and the amplified second signal output from the second transistor (20) 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 (16) and the second signal amplified by the second transistor (20) are combined in phase and a signal mode in which the first signal amplified by the first transistor (16) and the second signal amplified by the second transistor (20) 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.