Stacked Asymmetric Doherty Amplifier for Stable Driver Operation
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Solution Overview
Problem
The existing design of high frequency amplifiers, particularly when a driver amplifier and a Doherty amplifier are mounted on a printed circuit board, faces challenges in reducing size due to the need for a large printed circuit board and potential instability issues when the driver and carrier amplifiers are positioned close to each other.
Innovation Solution
The proposed solution involves an asymmetric Doherty amplifier configuration with a carrier amplifier and a peak amplifier, where the peak amplifier starts amplifying when the carrier amplifier reaches saturation. This configuration includes a driver amplifier, a branch circuit, a phase adjustment circuit, and substrates for mounting these components in a stacked manner, optimizing electrical length and phase differences to prevent instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the driver amplifier and carrier amplifier are positioned close to each other to reduce size, then the amplifier size is reduced, but the driver amplifier becomes unstable
Solution Approach 1:
The patent transitions from a planar layout to a three-dimensional stacked configuration. The driver amplifier is mounted on a first substrate while the carrier and peak amplifiers are mounted on a second substrate positioned above the first substrate. This vertical stacking enables compact integration while maintaining stable electrical connections through through-substrate conductors, resolving the contradiction between size reduction and stability.
2Reliability
If a large printed circuit board is used to accommodate all amplifiers on the same plane, then the driver amplifier remains stable, but the amplifier size increases
Solution Approach 1:
The invention moves away from the conventional planar arrangement on a single large PCB to a multi-layer stacked architecture. By placing the driver amplifier on one substrate and the Doherty amplifiers on another substrate above it, the design achieves compact volume while maintaining stable operation through controlled electrical paths and proper phase adjustment.
Solution Approach 2:
The amplifier system is segmented into two separate substrates: the first substrate for the driver amplifier and the second substrate for the carrier and peak amplifiers. This segmentation allows each amplifier to be optimally positioned and connected, reducing interference and maintaining stability while minimizing overall size.
3Reliability
If the electrical length from driver amplifier input to carrier amplifier output is optimized for stability, then the driver amplifier remains stable, but the phase adjustment complexity increases
Solution Approach 1:
The patent optimizes the electrical length parameter of the transmission path from the driver amplifier input to the carrier amplifier output to be within a specific range (0.05λ to 0.25λ, where λ is the wavelength at the center frequency). This parameter optimization ensures stable operation while simplifying the phase adjustment requirements, as the controlled electrical length naturally provides the necessary phase relationship.
Data Source
AI summary
A high frequency amplifier includes an asymmetric Doherty amplifier configured to amplify a high frequency signal having a wavelength λ, the high frequency signal being input, and the asymmetric Doherty amplifier including a carrier amplifier and a peak amplifier, the peak amplifier being configured to start an amplifying operation when an output of the carrier amplifier reaches a saturation region and having a saturation output different from a saturation output of the carrier amplifier, a driver amplifier configured to drive the asymmetric Doherty amplifier, a branch circuit configured to branch the high frequency signal amplified by the driver amplifier into an input path on a peak amplifier side and an input path on a carrier amplifier side, a phase adjustment circuit configured to delay either a phase of a signal input to the peak amplifier or a phase of a signal input to the carrier amplifier, the phase adjustment circuit being provided on either the input path on the peak amplifier side or the input path on the carrier amplifier, a first substrate on which the carrier amplifier and the peak amplifier are mounted, and a second substrate on which the driver amplifier, the branch circuit, and the phase adjustment circuit are mounted. An input terminal of the driver amplifier and an input terminal of the carrier amplifier are disposed at positions where the input terminal of the driver amplifier and the input terminal of the carrier amplifier project to each other when the second substrate is stacked on the first substrate. An electrical length from the input terminal of the driver amplifier to an output terminal of the carrier amplifier is set to a phase of (2n+1)×π, where n is an integer greater than or equal to 0.