Duplexer Tunable HF Filter Impedance Inverter Design
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Solution Overview
Problem
Existing tunable HF filters face challenges in tuning without altering important parameters like insertion loss, input impedance, and output impedance, limiting design flexibility and stability.
Innovation Solution
The duplexer design incorporates impedance converters that are either impedance inverters or admittance inverters, paired with series or parallel resonators, allowing for tunability without significant changes in these parameters, enabling more stable and flexible filter design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If tunable HF filters are used to replace multiple conventional filters, then the number of filters is reduced and design flexibility is improved, but important parameters such as insertion loss, input impedance, and output impedance change during tuning
Solution Approach 1:
Impedance converters are introduced as intermediary components between the resonators and the signal path. These converters act as mediators that isolate the tuning mechanism from the external circuit, preventing tuning-induced changes in insertion loss and impedance while maintaining frequency selectability.
Solution Approach 2:
The patent employs parameter changes by using tunable resonators whose resonant frequencies can be adjusted. By changing the resonant frequency parameter of the resonators while keeping the impedance converters fixed, the filter achieves tunability without affecting other critical parameters like insertion loss and impedance.
2Adaptability or versatility
If multiple conventional HF filters are used for different frequency bands, then each frequency band is covered, but the front-end module becomes large and manufacture is complicated and expensive
Solution Approach 1:
The patent implements a universal filter design where a single filter structure with tunable resonators can operate across multiple frequency bands. The impedance converters and resonator configuration enable the same hardware to be reconfigured for different frequency ranges, eliminating the need for separate filters for each band and reducing overall device complexity.
Solution Approach 2:
The filter incorporates dynamic elements (tunable resonators) that allow the filter characteristics to be changed operationally. This dynamic capability enables a single static physical structure to perform multiple frequency band functions by adjusting the resonant frequencies, thereby reducing the number of discrete filter components needed.
3Device complexity
If conventional HF filters are used, then the structure is simple, but the filter flanks are not steep and design freedom is limited
Solution Approach 1:
The filter is segmented into distinct functional components: impedance converters and resonators. This segmentation allows independent optimization of each component - the impedance converters provide the steep roll-off characteristics while the resonators provide frequency selectivity. The modular segmented structure maintains relative simplicity while achieving superior filter flank steepness.
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 approach allows for better tunability of HF filters, resulting in improved duplexer performance with steeper filter flanks and increased design freedom, suitable for various frequency band arrangements.
Implementation Method 1
each with an electroacoustic resonator
Implementation Method 2
Document US6404302B1 relates to a surface acoustic wave (SAW) filter
Implementation Method 3
The impedance converters in the Tx filter are impedance inverters
Implementation Method 4
The impedance converters in the Rx filter are admittance inverters
Data Source
Figure 1~3
Figure 4~6
Figure 7~8
AI summary
The invention relates to a duplexer with HF filters having reduced dependency on characteristic filter variables when tuning. According to the invention, a filter comprises base elements which are connected in series, and electroacoustic resonators which are connected in series between the base elements.