Multimode SAW Balance Filter for Opposite-Phase Power Handling
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Solution Overview
Problem
Existing balance filters lack power durability and face challenges in maintaining opposite-phase signal output after packaging, which affects amplitude and phase balance characteristics and pass band performance.
Innovation Solution
A balance filter design featuring first and second multimode surface acoustic wave filters connected in parallel, with specific configurations of IDTs and reflection electrodes to distribute power and maintain opposite-phase signal transmission, allowing for easy phase adjustment post-packaging and improved bandpass characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If all input power is applied to a single input SAW filter, then the balance filter can be configured simply, but the power durability deteriorates
Solution Approach 1:
The input filter is divided into multiple input SAW filters (first input SAW filter and second input SAW filter) that are connected in parallel. This segmentation distributes the input power across multiple filters, improving power durability while maintaining the overall balance filter functionality through parallel configuration.
2Reliability
If the number of IDTs in the input SAW filter is increased to improve power durability, then power durability improves, but the pass band characteristics deteriorate
Solution Approach 1:
Instead of increasing the number of IDTs in a single filter, the solution segments the filter into multiple parallel input SAW filters. Each filter maintains its original IDT configuration and pass band characteristics, while the parallel structure collectively handles higher power inputs without degrading individual filter performance.
3Manufacturing precision
If the input SAW filter is adjusted to maintain opposite-phase output, then amplitude and phase balance characteristics improve, but the adjustment difficulty increases due to the opposite-phase output requirement
Solution Approach 1:
A phase inversion circuit is introduced as an intermediary component connected to one of the output terminals. This circuit inverts the phase of the signal from one output, automatically maintaining the opposite-phase relationship between outputs without requiring complex adjustments to the input SAW filter itself, thereby simplifying the adjustment process.
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 design enhances power durability, facilitates easy balance adjustment, and improves amplitude and phase balance characteristics, while also achieving better bandpass performance and higher output impedance, reducing crosstalk and enhancing package layout flexibility.
Implementation Method 1
a first filter (40) that includes first multimode surface acoustic wave (SAW) filters (40a, 40b) connected in parallel; a second filter (60) that is connected to the first filter (40) and includes a second multimode SAW filter (60a)
Data Source
AI summary
A balance filter includes a first filter having first multimode surface acoustic wave (SAW) filters connected in parallel, a second filter that is connected to the first filter and includes a second multimode SAW filter, a first terminal connected to the first filter, and second terminals connected to the second filter. An input terminal of the balance filter is one of the first and second terminals, and an output terminal thereof is the other. Electric signals transmitted from the first to second filters or vice versa are in opposite phase. Electric signals are input or output via the second terminals in opposite phase.