Ladder-Type Filter Layout for Miniaturization Without Power Loss
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Solution Overview
Problem
Miniaturization of ladder-type filters for mobile communication terminals is required while maintaining power durability, as existing techniques face challenges in reducing size without compromising performance due to stress migration issues and increased complexity.
Innovation Solution
The design incorporates a combination of series and parallel arms, where one parallel arm without resonance properties is used between series arm resonators, and an inductor is added in series to improve attenuation and isolation characteristics, allowing for miniaturization without reducing power durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the ladder-type filter is miniaturized by reducing SAW resonator size, then the filter size is reduced, but power durability is reduced due to stress migration
Solution Approach 1:
The parallel arm is divided into multiple parallel resonators connected in series. This segmentation allows each individual resonator to have reduced size while the combined structure maintains the necessary electrical characteristics and power handling capability, thus resolving the contradiction between miniaturization and power durability
Solution Approach 2:
The invention changes the electrical parameters by configuring multiple parallel resonators with specific impedance values (e.g., 50Ω each) connected in series to achieve an equivalent 25Ω impedance. This parameter transformation allows the use of smaller resonators while maintaining the required electrical performance and power durability
2Manufacturing precision
If the number of ladder stages is increased to keep the floor level low, then the floor level is improved, but the filter size is enlarged
Solution Approach 1:
The invention achieves low floor level with fewer stages by optimizing the impedance parameters of the parallel arm resonators. By setting each parallel resonator to 50Ω and connecting them in series to achieve 25Ω equivalent impedance, the filter maintains excellent floor level characteristics without requiring an increased number of stages, thus preventing size enlargement
3Volume of moving object
If a simple configuration with fewer elements is used for miniaturization, then the filter size is reduced, but the floor level cannot be kept low
Solution Approach 1:
The invention uses precise impedance parameter design of the parallel resonators (50Ω each, series-connected to achieve 25Ω equivalent) to maintain low floor level with a reduced number of elements. This parameter optimization allows fewer elements to be used while still achieving the desired floor level performance
Solution Approach 2:
The invention uses multiple identical parallel resonators with the same impedance characteristics (50Ω) connected in series. This copying approach simplifies the design process and allows predictable floor level performance with fewer elements, as the identical configurations can be optimized together rather than individually
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 enables the maintenance of a low floor level while ensuring miniaturization and power durability, preventing issues like stress migration and size enlargement, and improving the filter's performance in communication systems.
Implementation Method 1
the size of a surface acoustic wave (SAW) resonator must be miniaturized
Implementation Method 2
one of the parallel arms does not have resonance characteristic is arranged in parallel between 2 series arm resonators
Data Source
AI summary
A ladder-type filter includes a plurality of series arms and a plurality of parallel arms, in which one of the parallel arms does not have resonance characteristic is arranged in parallel between two series arm resonators of the plurality of series arms. The ladder-type filter may be included in a duplexer and/or a module.