Parallel DMS SAW Filter Layout for Broad Passband Coverage
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Solution Overview
Problem
Existing filters with broad frequency bands face challenges in achieving minimal insertion loss and sufficient edge steepness, making it difficult to suppress adjacent bands, especially when using filters with large bandwidths for Carrier Aggregation in mobile radio applications.
Innovation Solution
A filter arrangement using two DMS filters connected in parallel with differing center frequencies, combined with a serial resonator and anti-phase coupling converters, and a dielectric covering layer on a lithium niobate substrate to achieve a broad passband with low insertion loss and steep edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a single filter with large bandwidth is used to cover broad frequency bands, then the bandwidth coverage is improved, but the impedance adjustment becomes difficult and insertion loss increases
Solution Approach 1:
The patent divides a single large-bandwidth filter into two separate filters with smaller bandwidths, each optimized for a specific frequency range. This segmentation allows each filter to achieve better impedance matching and lower insertion loss in its respective band, while collectively covering the broader frequency range through parallel connection.
2Area of moving object
If a single filter with large bandwidth is used to cover broad frequency bands, then the bandwidth coverage is improved, but the edge steepness decreases making suppression of adjacent bands difficult
Solution Approach 1:
By segmenting the broad band into two separate filters, each filter can be designed with optimized edge characteristics for its specific frequency range. This enables steeper roll-off and better suppression of adjacent bands, as each filter focuses on providing sharp transitions at its boundaries rather than attempting to maintain edge steepness across the entire broad bandwidth.
3Manufacturing precision
If two filters are used to cover broad frequency bands by dividing into sub-bands, then the impedance adjustment and edge steepness are improved, but the device complexity increases
Solution Approach 1:
The patent combines two separate filters in a parallel configuration to achieve the desired broad bandwidth coverage. This merging approach allows each filter to maintain its optimized edge steepness and impedance characteristics while collectively providing the comprehensive frequency coverage, balancing performance requirements with structural complexity.
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 solution enables the simultaneous coverage of two closely adjacent mobile bands with low insertion loss and effective suppression of adjacent bands, suitable for Carrier Aggregation Mode, while minimizing power losses and reducing geometrical dimensions.
Implementation Method 1
SAW filter with a large bandwidth
Implementation Method 2
two DMS filters connected in parallel
Data Source
AI summary
A filter arrangement with a large bandwidth is specified, wherein a first and a second filter are connected in parallel between a first and a second node. Both filters are configured as DMS filters and both comprise two DMS tracks each, connected in series. The two filters have different center frequencies and create a common passband together.