Asymmetrical Doherty Amplifier Layout for Stable 3D RF Mounting
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Solution Overview
Problem
High frequency amplifiers face challenges in heat dissipation and stability due to close proximity of driver and peak amplifiers, leading to potential electrical instability and oscillation, especially in miniaturized three-dimensional mounting configurations.
Innovation Solution
The design incorporates an asymmetrical Doherty amplifier with a phase adjusting circuit that sets the electrical length between the driver and peak amplifier terminals to achieve antiphase signal phases, and a base member for heat dissipation, along with a grounded metal layer to shield electromagnetic interference, ensuring stable operation and efficient heat management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the driver amplifier and peak amplifier are mounted close to each other in a three-dimensional configuration, then the device size is reduced, but electrical instability and oscillation occur due to electromagnetic interference
Solution Approach 1:
A grounded metal layer is introduced as an intermediary shielding structure between the driver amplifier and peak amplifier. This ground layer acts as a barrier to electromagnetic fields, preventing interference while allowing the amplifiers to be mounted in close proximity for compact device size.
Solution Approach 2:
The shielding structure is applied locally between specific amplifier components rather than throughout the entire device. The grounded metal layer is positioned specifically between the driver and peak amplifiers where electromagnetic interference is most problematic, providing targeted protection while minimizing overall device volume.
2Volume of moving object
If the driver amplifier and peak amplifier are mounted close to each other, then space is saved, but heat dissipation becomes difficult due to restricted airflow and proximity
Solution Approach 1:
Heat dissipation structures are applied locally to the amplifiers that generate the most heat. The driver amplifier and peak amplifier are equipped with dedicated heat dissipation structures positioned to maximize thermal release while maintaining compact overall device dimensions.
Solution Approach 2:
The grounded metal layer serves dual functions as both an electromagnetic shield and a thermal management structure. It acts as an intermediary that does not obstruct heat dissipation pathways while providing EMI shielding, allowing close mounting without compromising thermal performance.
3Volume of moving object
If miniaturization is achieved through three-dimensional mounting, then device size is reduced, but heat dissipation efficiency decreases
Solution Approach 1:
Heat dissipation structures are strategically positioned on the amplifiers to maximize thermal release efficiency within the compact three-dimensional configuration. The structures are placed on surfaces with optimal exposure for heat release while maintaining the miniaturized device form factor.
4Device complexity
If the electrical length between driver and peak amplifier is not properly adjusted, then the device structure is simplified, but oscillation occurs due to phase interference
Solution Approach 1:
The electrical length between the driver amplifier and peak amplifier is precisely controlled by adjusting the physical dimensions of the transmission path. By changing the length parameter of the transmission line to satisfy specific phase conditions, oscillation is prevented while maintaining a relatively simple circuit configuration without requiring complex additional components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration stabilizes the electric characteristics of the peak amplifier, prevents oscillation, and enhances heat dissipation, resulting in a compact, reliable high frequency amplifier with improved power efficiency and reduced costs.
Implementation Method 1
a base member that mounts the first circuit board and the second circuit board
Implementation Method 2
The phase adjusting circuit is provided on at least one of the input paths of the peak amplifier and the carrier amplifier to delay at least one of phases of input signals of the peak amplifier and the carrier amplifier. The electrical length from an output terminal of the driver amplifier to the input terminal of the peak amplifier, when converted based on a phase of the input high frequency signal, is from (2n+1)×π−π/4 to (2n+1)×π+π/4
Data Source
AI summary
A high frequency amplifier includes an asymmetrical Doherty amplifier having a carrier amplifier, a peak amplifier, a branch circuit, and a phase adjusting circuit, a driver amplifier, and a base member mounting a first circuit board mounting the driver amplifier, the carrier amplifier, and the peak amplifier and a second circuit board mounting the circuits. The branch circuit divides a path of a RF signal into input paths of the peak and carrier amplifiers. The driver amplifier, the carrier amplifier, and the peak amplifier have rear surfaces in contact with the base member. The electrical length from the output terminal of the driver amplifier to the input terminal of the peak amplifier, when converted based on a phase of the signal, is from (2n+1)×π−α/4 to (2n+1)×π+π/4, where n is an integer greater than or equal to zero.