RF Module Grounding Segmentation for Noise Suppression
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Solution Overview
Problem
In multi-stage power amplifiers used in mobile communication devices, the amplification characteristic is degraded due to high-power radio-frequency signals flowing back through the ground electrode layer, causing noise and heat dissipation issues.
Innovation Solution
A radio-frequency module design where the ground terminals of cascade-connected amplification elements are not electrically connected via the first ground electrode layer on the mounting substrate, extending the electrical path and reducing noise entry from the power stage to the drive stage, thereby suppressing amplification characteristic degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ground terminals of cascade-connected amplification elements are electrically connected via the first ground electrode layer, then grounding performance is improved, but high-power radio-frequency signals flow back to preceding stages causing noise and amplification characteristic degradation
Solution Approach 1:
The ground electrode layer is segmented into multiple layers (first ground electrode layer and second ground electrode layer). The first ground electrode layer is positioned closer to the power amplification circuit while the second ground electrode layer is positioned closer to the drive amplification circuit. This segmentation allows each ground layer to serve its respective amplification stage independently, preventing noise coupling while maintaining effective grounding for both stages.
Solution Approach 2:
Different ground electrode layers are assigned to different functional regions: the first ground electrode layer serves the power amplification circuit region, while the second ground electrode layer serves the drive amplification circuit region. This local quality differentiation ensures that grounding is optimized for each specific amplification stage without causing cross-stage noise interference.
2Area of stationary object
If circuit elements are mounted at high density, then space utilization is improved, but heat dissipation becomes more difficult for amplification circuits and passive elements
Solution Approach 1:
Heat dissipation is addressed by transitioning from two-dimensional surface mounting to three-dimensional heat management. Heat generating components are mounted on the front surface while dedicated heat dissipation electrodes are provided on the rear surface of the substrate. This vertical separation allows efficient heat removal through the substrate thickness dimension, enabling high-density front-surface mounting without compromising thermal management.
Data Source
AI summary
A radio-frequency module includes: a transmission power amplifier that includes first and second amplification transistors that are cascade connected to each other; and a mounting substrate that has first and second main surface that face each other, the transmission power amplifier being mounted on the first main surface. The first amplification transistor is arranged in a final stage and has a first emitter terminal. The second amplification transistor is arranged in a stage preceding the first amplification transistor and has a second emitter terminal. The mounting substrate has first to fourth ground electrode layers in order of proximity to the first main surface. The first emitter terminal and the second emitter terminal are not electrically connected to each other via an electrode on the first main surface and are not electrically connected to each other via the first ground electrode layer.