Acoustic Wave Tunable Filter With Switched Resonator Bands
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Solution Overview
Problem
Tunable filters with acoustic wave resonators and variable capacitors face limitations in their frequency range adaptability, making it difficult to cover various communication bands as the difference in frequency between resonant and anti-resonant points is not adequately tunable.
Innovation Solution
A tunable filter design incorporating a ladder network of series-arm and parallel-arm resonant circuits with multiple acoustic wave resonators and a switching circuit that connects these resonators to a variable capacitor, allowing for broader frequency tuning by adjusting capacitance and selecting different resonant circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single acoustic wave resonator and variable capacitor are used in a ladder network, then the circuit structure is simple, but the tunable frequency range is limited due to the fixed difference between resonant and anti-resonant points
Solution Approach 1:
The patent divides the acoustic wave resonant circuit into multiple segments (first and second acoustic wave resonant circuits) with different resonant frequencies. Each segment can be selectively connected to the variable capacitor through switching circuits, allowing the filter to access different frequency ranges by switching between segments rather than relying on a single resonator's limited tuning range.
Solution Approach 2:
The variable capacitor is designed to serve multiple functions: it can be connected to different acoustic wave resonant circuits through switching circuits, and it can adjust capacitance values to fine-tune the resonant frequencies within each circuit segment. This multi-functional design enables a single component to contribute to extended frequency coverage across multiple communication bands.
2Adaptability or versatility
If the variable capacitor capacitance range is increased to extend tuning range, then the frequency coverage improves, but the difference between resonant and anti-resonant points cannot be adequately adjusted
Solution Approach 1:
By segmenting the resonant circuit into multiple circuits with different base resonant frequencies, the patent enables coarse frequency adjustment through switching between segments. This segmentation allows the variable capacitor to focus on fine-tuning within each segment rather than attempting to cover the entire frequency range alone, improving the precision of resonant and anti-resonant point adjustment.
Solution Approach 2:
The patent introduces switching circuits that dynamically reconfigure the connection between the variable capacitor and different acoustic wave resonant circuits based on the desired frequency range. This dynamic reconfiguration allows the system to adaptively select the appropriate resonant circuit segment, enabling precise control over the difference between resonant and anti-resonant points across different operating conditions.
3Adaptability or versatility
If multiple acoustic wave resonant circuits with different resonant frequencies are introduced, then the pass-band frequency can be tuned over a broader range, but the device complexity increases
Solution Approach 1:
The patent combines multiple acoustic wave resonant circuits with different resonant frequencies into a single filter structure, where switching circuits selectively connect these circuits to the variable capacitor. This merging approach allows the filter to achieve broad frequency tuning capability while maintaining a relatively compact and integrated design, rather than requiring separate filter modules for different frequency ranges.
Solution Approach 2:
The switching circuits provide dynamic reconfiguration capability, allowing the filter to adapt its resonant characteristics by connecting different acoustic wave resonant circuits to the variable capacitor based on the desired pass-band frequency. This dynamic switching mechanism enables broad frequency coverage without requiring all resonant circuits to be simultaneously active, thereby managing device complexity effectively.
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 extends the tunable frequency range, enabling the filter to adapt to multiple communication bands with improved attenuation and bandpass characteristics, reducing insertion loss and enhancing communication signal transmission while suppressing unwanted frequencies.
Implementation Method 1
a tunable filter including a ladder connection of a series-arm resonant circuit and a parallel-arm resonant circuit, each having an acoustic wave resonator
Implementation Method 2
a variable capacitor that selectively connects the first acoustic wave resonant circuit and the second acoustic wave resonant circuit
Data Source
AI summary
A tunable filter includes a series-arm resonant circuit, and a parallel-arm resonant circuit. The series-arm resonant circuit includes a group of acoustic wave resonant circuits that have different resonant frequencies, a variable capacitor, and switching circuits. The parallel-arm resonant circuit includes another group of acoustic wave resonant circuits that have different resonant frequencies, a variable capacitor, and switching circuits. For example, the difference in pass-band frequency caused by the difference in resonant frequency between the acoustic wave resonant circuit in the group and the acoustic wave resonant circuit in the other group is greater than the maximum difference in pass-band frequency resulting from the variable range of capacitance of the variable capacitor.