Doherty Amplifier Matching Circuit for Peak Gain and Low Distortion
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Solution Overview
Problem
In Doherty amplifier circuits, there is a challenge in improving efficiency while suppressing distortion, particularly in high-output high-frequency applications such as base stations in mobile communication.
Innovation Solution
The proposed solution involves a Doherty amplifier circuit with a divider that splits the input signal into multiple signals, each amplified by a main amplifier and peak amplifiers. The circuit includes matching circuits between the divider and each amplifier, with specific impedance matching configurations to optimize gain and efficiency. The absolute value of return loss seen from the divider toward the second matching circuit is larger than that seen toward the first matching circuit, enhancing the gain of the peak amplifier and suppressing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the gain of the peak amplifier is increased to improve efficiency, then the overall efficiency of the Doherty amplifier circuit is improved, but distortion increases
Solution Approach 1:
The patent applies different return loss characteristics to different matching circuits: the first matching circuit (connected to the main amplifier) has a smaller return loss absolute value, while the second matching circuit (connected to the peak amplifier) has a larger return loss absolute value. This local differentiation allows the peak amplifier to operate with higher gain and efficiency while the main amplifier maintains better linearity, thereby reducing overall distortion despite the high efficiency operation of the peak amplifier.
2Reliability
If the return loss of the first matching circuit is reduced to improve main amplifier performance, then the main amplifier operates more efficiently, but the gain of the peak amplifier is reduced
Solution Approach 1:
The patent implements asymmetric return loss characteristics across the matching circuits. The first matching circuit is optimized with a smaller return loss absolute value to enhance main amplifier performance and reliability, while the second matching circuit is designed with a larger return loss absolute value to maximize peak amplifier gain. This localized optimization of each matching circuit's return loss characteristic allows both amplifiers to operate at their optimal performance points simultaneously.
Data Source
AI summary
A Doherty amplifier circuit includes a divider dividing a received input signal into a first signal and a second signal, a main amplifier amplifying the first signal and output an amplified signal as a fourth signal, a first peak amplifier amplifying the second signal and output an amplified signal as a fifth signal, a combiner combining the fourth signal and the fifth signal into a combined signal and output the combined signal as an output signal to an output terminal, a first matching circuit connected between the divider and the main amplifier, and a second matching circuit connected between the divider and the first peak amplifier. In an operation band, an absolute value of a return loss seen from the divider toward the second matching circuit is larger than an absolute value of a return loss seen from the divider toward the first matching circuit.