Doherty Amplifier Phase Adjustment for Backoff Oscillation Control
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Solution Overview
Problem
Conventional Doherty amplifiers experience oscillation phenomena during backoff operations due to signal reflection between peak amplifiers, which existing splitter circuits cannot effectively mitigate.
Innovation Solution
Incorporating a signal splitter circuit with a T-branch circuit and a signal delay circuit, along with a phase adjustment circuit to adjust the phase of return signals, ensuring the sum of phases between auxiliary amplification elements is not zero, thereby preventing oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional splitter circuit is used to split signals in a Doherty amplifier, then the amplifier can operate with standard circuit configuration, but oscillation occurs during backoff operations due to signal reflection between peak amplifiers
Solution Approach 1:
A phase adjustment circuit is introduced as an intermediary component between the splitter circuit and the peak amplifiers. This circuit specifically targets and adjusts the phase of return signals reflected between peak amplifiers during backoff operations, preventing oscillation without requiring complete redesign of the overall amplifier configuration.
Solution Approach 2:
The invention changes the phase parameter of return signals by introducing a phase shift that ensures the sum of phases between auxiliary amplification elements is not zero. This parameter modification prevents constructive interference that causes oscillation, while maintaining the standard Doherty amplifier architecture.
2Ease of operation
If the phase of return signals is not adjusted, then the circuit operates simply, but oscillation phenomenon occurs between auxiliary amplification elements during backoff operations
Solution Approach 1:
The phase adjustment circuit performs preliminary phase modification on return signals before they can cause oscillation. By adjusting the phase in advance during backoff operations, the circuit prevents oscillation from occurring while maintaining simple operational procedures.
3Reliability
If a phase adjustment circuit is added to prevent oscillation, then operational stability is improved, but device complexity increases
Solution Approach 1:
The phase adjustment circuit serves as a targeted intermediary that addresses only the specific oscillation problem without requiring comprehensive system redesign. This localized approach improves operational stability while adding minimal complexity compared to complete system reconfiguration.
Data Source
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AI summary
A Doherty amplifier includes: a first main amplification element (5) to amplify a first signal; a second main amplification element (6) to amplify the first signal amplified by the first main amplification element (5) ; a first auxiliary amplification element (7) to amplify a second signal; a second auxiliary amplification element (8) to amplify the second signal amplified by the first auxiliary amplification element (7); a combination circuit (9) to combine the first signal amplified by the second main amplification element (6) and the second signal amplified by the second auxiliary amplification element (8); and a phase adjustment circuit (13) connected between the first auxiliary amplification element (7) and the second auxiliary amplification element (8). The Doherty amplifier is then configured in such a way that the phase adjustment circuit (13) adjusts either the phase of a return signal going to the first auxiliary amplification element (7) as a result of passage of the first signal amplified by the second main amplification element (6) through the second auxiliary amplification element (8) as the return signal, or the phase of the return signal going to the second auxiliary amplification element (8) as a result of reflection of the return signal by the first auxiliary amplification element (7), at a time of a backoff operation of the second auxiliary amplification element (8), in such a way that the sum of the phase of the return signal going to the first auxiliary amplification element (7) and the phase of the return signal going to the second auxiliary amplification element (8) is not equal to 0 degrees in the operating frequency band of the first signal.