Differential SAW Ladder Filter Layout for Wider Passbands
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wireless communication devices face challenges in widening the pass band of surface acoustic wave devices used for filtering high-power differential signals, resulting in increased signal loss due to the limited configuration of ladder filters defined only by resonators.
Innovation Solution
A filter device configuration that includes two ladder filters with inductors connected between parallel arm resonators and ground, allowing for a widened pass band and increased electric power handling capability by distributing the input signal across multiple filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the pass band of a surface acoustic wave device is widened by using a ladder filter configuration, then the frequency range is expanded, but signal loss increases
Solution Approach 1:
The filter is divided into multiple ladder filters (first ladder filter and second ladder filter) with different pass bands. Each ladder filter handles a specific frequency range, allowing the overall system to achieve a wider total pass band while maintaining low signal loss in each segment. The segmentation of the filter structure enables independent optimization of each section's characteristics.
Solution Approach 2:
Multiple ladder filters with different pass bands are combined in parallel to form a composite filter system. The first ladder filter and second ladder filter are connected to the same input and output terminals, merging their filtering capabilities to achieve a wider overall pass band while maintaining low signal loss through the combination of multiple specialized sections.
2Device complexity
If a single ladder filter is used for high-power differential signals, then the circuit is simple, but electric power handling capability is limited
Solution Approach 1:
The high-power filtering task is segmented across multiple ladder filters operating in parallel. The first ladder filter and second ladder filter each handle portions of the differential signal, distributing the power handling burden and enabling the system to process higher total power while maintaining circuit simplicity through modular repetition of the ladder filter structure.
Solution Approach 2:
Different ladder filters are configured with optimized characteristics for their specific roles in the differential signal path. The first ladder filter and second ladder filter may have different component values and configurations tailored to their respective functions, allowing each section to operate optimally under high-power conditions while contributing to the overall power handling capability.
3Adaptability or versatility
If the pass band is widened in existing surface acoustic wave devices, then frequency range is expanded, but signal loss and heat generation increase
Solution Approach 1:
The filtering function is segmented into multiple specialized ladder filters, each optimized for specific frequency ranges. This segmentation allows each filter section to operate more efficiently with lower losses, reducing overall heat generation while achieving a wider combined pass band. The modular structure enables better thermal management through distributed power dissipation.
Solution Approach 2:
Multiple low-loss ladder filters are merged in parallel to create a wide pass band system. By combining filters that each maintain low signal loss and heat generation in their respective frequency ranges, the overall system achieves wide frequency coverage without the excessive heat generation that would result from attempting to widen a single filter's 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
The proposed filter device achieves a wider pass band while enhancing electric power handling capability, reducing signal loss and heat generation, and maintaining signal balance across the filters.
Implementation Method 1
an inductor connected between a ground terminal and a parallel arm resonator included in at least one parallel arm
Implementation Method 2
a surface acoustic wave device in which two ladder filters each including a plurality of SAW resonators
Implementation Method 3
two ladder filters each including a plurality of SAW resonators connected in series are disposed on a piezoelectric substrate
Data Source
AI summary
A filter device includes a first filter including a first input terminal, a first output terminal, a first series arm including first series arm resonators, and first parallel arms connected to the first series arm and each including a first parallel arm resonator, the first filter having a pass band in a predetermined frequency band, a second filter including a second input terminal, a second output terminal, a second series arm including second series arm resonators, and second parallel arms connected to the second series arm and each including a second parallel arm resonator, the second filter having a pass band in the predetermined frequency band, a substrate including the first and second filters, and an inductor connected between a ground terminal and a parallel arm resonator included in at least one parallel arm of the first and second parallel arms.