Elastic Wave Filter Circuit With Split Inductors for Size and Q Value
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Solution Overview
Problem
Conventional elastic wave devices face challenges in reducing size while maintaining filter characteristics, as replacing surface-mount inductor elements with wiring patterns leads to a degradation of the Q value and filter performance.
Innovation Solution
The elastic wave device incorporates an impedance matching element, a switch, and multiplexers on a substrate, with inductors and capacitors strategically placed to reduce size without deteriorating filter characteristics, including inductors defined by wiring patterns and capacitors connected between switch terminals and multiplexers, and ground potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If surface-mount inductor elements are replaced with wiring patterns to reduce size, then the device size is reduced, but the Q value degrades and filter characteristic deteriorates
Solution Approach 1:
The patent divides the inductor function into two segments: a surface-mount inductor element for impedance matching (maintaining high Q value) and wiring patterns for additional inductance (enabling size reduction). This segmentation allows each component to fulfill its specific role optimally, resolving the contradiction between size reduction and filter characteristic maintenance.
Solution Approach 2:
The patent merges the function of impedance matching (traditionally requiring a single large inductor) with the function of circuit connectivity (wiring patterns). By combining a surface-mount inductor with strategically placed wiring patterns, the design achieves both compact size and high Q value performance, simultaneously addressing size reduction and filter characteristic requirements.
2Reliability
If surface-mount inductor elements are used to maintain Q value, then filter characteristic is maintained, but the device size increases
Solution Approach 1:
The patent segments the inductance requirement into two parts: a small surface-mount inductor for critical impedance matching functions (preserving Q value) and distributed wiring pattern inductance for less critical impedance adjustment (enabling size reduction). This segmentation allows the device to maintain filter characteristics while minimizing overall size.
Solution Approach 2:
The patent changes the parameter distribution of inductance throughout the circuit. Instead of concentrating all inductance in a single large component, it distributes inductance across multiple locations (wiring patterns) and uses a smaller surface-mount inductor with optimized inductance value. This parameter redistribution enables size reduction while maintaining the necessary Q value for 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 allows for a reduction in size without compromising filter characteristics, maintaining excellent impedance matching and Q value performance.
Implementation Method 1
at least one inductor that is provided on the substrate and has an inductance smaller than an inductance of the impedance matching element
Implementation Method 2
The switch includes at least one capacitor that is connected between the first switch terminal and at least one of the multiplexers
Data Source
AI summary
An elastic wave device includes an impedance matching element, a switch that switches a connection state between a first switch terminal connected to the impedance matching element and second switch terminals, multiplexers connected to the second switch terminals, a substrate, and at least one inductor on the substrate and has an inductance smaller than an inductance of the impedance matching element. At least one of the second switch terminals and at least one of the multiplexers are connected with the first inductor interposed therebetween.