Elastic Wave Multiplexer Segmentation for Compact Low-Loss Front Ends
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Solution Overview
Problem
In multiplexers with multiple filters connected to a single antenna terminal, the filter characteristics of one filter are significantly affected by the others, leading to increased insertion loss due to reflection characteristics, making it challenging to reduce propagation loss while maintaining a compact size.
Innovation Solution
A multiplexer configuration with a common terminal and multiple input/output terminals, where the first filter includes at least two elastic wave resonators between the common and first input/output terminals, and a second filter between the common and second input/output terminals, with a reflection coefficient of the initial-stage filter section being larger than the subsequent-stage filter section, reducing connection loss and overall insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multiple filters are connected in parallel at a single antenna terminal to reduce device size, then the multiplexer becomes compact, but the insertion loss increases due to reflection characteristics of other filters affecting the pass band
Solution Approach 1:
The first filter is segmented into an initial-stage filter section and a subsequent-stage filter section. The initial-stage filter section includes at least one elastic wave resonator and is configured to provide a large reflection coefficient in the second pass band, while the subsequent-stage filter section provides the main filtering function. This segmentation allows the first filter to simultaneously achieve compact size and reduced insertion loss by reflecting signals in the second pass band before they reach the subsequent-stage filter section.
Solution Approach 2:
Different sections of the first filter are assigned different local qualities: the initial-stage filter section is designed with high reflection characteristics specifically for the second pass band, while the subsequent-stage filter section is optimized for the first pass band filtering. This local quality differentiation allows each section to perform its specific function optimally, resolving the contradiction between compact size and insertion loss.
2Adaptability or versatility
If filters are connected in parallel at a single antenna terminal to handle multiple frequency bands, then multiband capability is achieved, but the filter characteristics are greatly affected by other filters leading to increased propagation loss
Solution Approach 1:
The initial-stage filter section of the first filter is designed to preemptively reflect signals in the second pass band before these signals can pass through to affect the second filter's performance. By applying preliminary anti-action (reflection) in the second pass band, the harmful effect of filter interaction is prevented before it can cause increased propagation loss, while still maintaining multiband capability.
3Loss of energy
If the reflection coefficient of a filter in another pass band is increased to reduce connection loss, then the insertion loss of other filters is reduced, but the return loss in that pass band increases
Solution Approach 1:
The first filter is divided into two sections with different functions: the initial-stage filter section handles reflection in the second pass band to reduce connection loss, while the subsequent-stage filter section maintains proper filtering characteristics for the first pass band. This segmentation allows the system to tolerate higher return loss in the second pass band (generated by the initial-stage section) while still achieving reduced connection loss and maintaining performance in the first pass band.
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 significantly reduces connection loss and insertion loss, enabling smaller multiplexers with improved high-frequency signal propagation characteristics.
Implementation Method 1
a first filter that includes at least two elastic wave resonators between the common terminal and the first input/output terminal, the first filter including a first pass band
Implementation Method 2
A reflection coefficient of the initial-stage filter section in the second pass band when the initial-stage filter section is viewed from the common terminal side as a single component is larger than a reflection coefficient of the subsequent-stage filter section in the second pass band
Data Source
AI summary
A multiplexer includes filters connected to each other at a common terminal, a low-frequency filter with a first pass band, and a high-frequency filter with a second pass band that is higher than the first pass band. The low-frequency filter includes an initial-stage filter section including at least one first elastic wave resonator located on the common terminal side among at least two elastic wave resonators, and a subsequent-stage filter section that includes a second elastic wave resonator other than the at least one first elastic wave resonator. A reflection coefficient in the second pass band when the initial-stage filter section is viewed from the common terminal side as a single component is larger than a reflection coefficient in the second pass band when the subsequent-stage filter section is viewed from the common terminal side as a single component.