RF Module Filter Layout for Power Amplifier Heat Stability
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Solution Overview
Problem
The semiconductor module's signal-transfer characteristics deteriorate due to temperature-dependent frequency changes caused by the power amplifier's heat, affecting the performance of surface acoustic wave filters.
Innovation Solution
A radio frequency module is designed with a transmission filter having a smaller temperature coefficient of frequency (TCF) than the reception filter, and the transmission filter is placed closer to the power amplifier, while the reception filter is farther away, to minimize the impact of temperature changes on signal transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a surface acoustic wave filter is used as a filter on the semiconductor module, then the filter can be mounted on the wiring board, but the passing characteristics of the filter exhibit temperature-dependent frequency change due to heat from the power amplifier, resulting in deterioration of signal-transfer characteristics
Solution Approach 1:
The patent applies local quality by assigning different TCF characteristics to different filters based on their specific locations and thermal environments. The transmission filter is selected with a smaller absolute TCF value to withstand higher temperatures near the power amplifier, while the reception filter can have a larger TCF value since it operates in a cooler region. This localized optimization of filter characteristics resolves the contradiction by matching each filter's temperature stability to its specific thermal exposure.
Solution Approach 2:
The patent changes the parameter of TCF value selection based on the thermal environment. By selecting filters with appropriate TCF characteristics (smaller absolute TCF for transmission filter near heat source, larger TCF for reception filter farther from heat source), the system adapts to temperature variations and maintains signal-transfer characteristics despite the presence of heat-generating power amplifiers.
2Area of stationary object
If the transmission filter is placed closer to the power amplifier, then the layout is more compact, but the temperature change from the power amplifier affects the filter's frequency characteristics
Solution Approach 1:
The patent applies local quality by selecting filters with TCF characteristics matched to their local thermal environments. The transmission filter positioned near the power amplifier (high temperature zone) is selected with a smaller absolute TCF value to maintain stability under thermal stress, while the reception filter in the cooler zone can have a larger TCF value. This resolves the contradiction by making the system tolerant to temperature variations through localized parameter optimization.
3Reliability
If the reception filter is placed farther from the power amplifier, then the temperature impact is reduced, but the overall module size increases
Solution Approach 1:
The patent resolves this contradiction by applying local quality optimization where each filter's TCF characteristic is matched to its specific thermal zone. The reception filter can be positioned farther from the power amplifier and uses a TCF characteristic that is less sensitive to temperature changes, allowing for relaxed spacing requirements while maintaining stability. This enables compact module design without compromising reception filter performance.
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 reduces the deterioration of signal-transfer characteristics caused by temperature changes, maintaining the module's performance and stability.
Implementation Method 1
a transmission filter (a first acoustic wave filter) disposed on one of the first principal surface and the second principal surface; and a reception filter (a second acoustic wave filter) disposed on one of the first principal surface and the second principal surface
Data Source
AI summary
A radio frequency module includes: a module board that includes a first principal surface and a second principal surface on opposite sides of the module board; a power amplifier disposed on the module board; a low noise amplifier disposed on the module board; a transmission filter (a first acoustic wave filter) disposed on one of the first principal surface and the second principal surface; and a reception filter (a second acoustic wave filter) disposed on one of the first principal surface and the second principal surface. An absolute value of a temperature coefficient of frequency (TCF) of the transmission filter is smaller than an absolute value of a TCF of the reception filter, and a distance between the transmission filter and the power amplifier is shorter than a distance between the reception filter and the power amplifier.