Ladder Filter Resonator Isolation Design
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Solution Overview
Problem
Existing signal separation devices face challenges in achieving improved isolation characteristics when the passbands of transmission and reception filters are adjacent to each other, as they often result in degraded isolation characteristics and increased device size due to restrictive ground electrode arrangements and sub-resonant response suppression.
Innovation Solution
A signal separation device with a ladder filter configuration, featuring a series arm and parallel arms with resonators, where the parallel arm resonators have lower capacitance and higher resonant frequencies than the series arm resonators, and are connected between the series arm and ground, enhancing isolation characteristics in the high-frequency passband without altering the reception filter design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ground potential isolation is implemented to improve isolation characteristics, then isolation characteristics are improved, but device size increases due to routing wiring lines and restricting ground electrode arrangement
Solution Approach 1:
The patent extracts the ground isolation function from the physical ground electrode arrangement and relocates it to the resonator circuit design. By incorporating isolation functionality into the resonator's electrical characteristics rather than physical ground separation, the device achieves isolation without requiring additional wiring space or ground electrode restrictions.
Solution Approach 2:
The patent changes the electrical parameters of the resonator (capacitance and resonant frequency) to achieve isolation characteristics. By adjusting the resonator's capacitance value and resonant frequency to be higher than the passband frequency, the system achieves ground isolation effects through parameter optimization rather than physical structural changes.
2Object-generated harmful factors
If a single parallel-arm resonator is used as a notch filter to suppress sub-resonant response, then sub-resonant response is suppressed, but isolation characteristics are degraded when passbands are close to each other
Solution Approach 1:
The patent applies local quality by designing different resonator characteristics for different frequency regions. The resonator is specifically tuned with capacitance and resonant frequency parameters that are higher than the passband frequency, creating localized suppression effects precisely where needed (in the passband region) without affecting other frequency regions.
Solution Approach 2:
The patent uses dynamic resonator design where the resonator's electrical characteristics (capacitance and resonant frequency) are made adjustable or optimizable. This allows the system to dynamically adapt to different passband configurations, maintaining isolation characteristics even when passbands are close together, unlike fixed single-point suppression.
3Productivity
If transmission filter and reception filter passbands are placed adjacent to each other to reduce frequency spacing, then frequency utilization is improved, but isolation characteristics are degraded
Solution Approach 1:
The patent achieves adjacent passband configuration with maintained isolation by changing the resonator's electrical parameters. Specifically, the resonator is designed with capacitance and resonant frequency values higher than the passband frequency, creating a filtering effect that maintains isolation even when transmission and reception passbands are closely spaced.
Solution Approach 2:
The patent replaces physical ground isolation mechanisms with electrical resonator-based isolation. Instead of using physical distance or ground electrode arrangements to achieve isolation, the system uses the resonator's electrical characteristics (impedance, resonant frequency, capacitance) to provide isolation, allowing closer passband spacing without compromising isolation performance.
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 effectively improves isolation characteristics in the high-frequency passband while reducing the device size by adjusting the number and width of electrode fingers in the transmission filter's circuit, without changing the ground patterns or increasing connection vias, thus maintaining transmission and reception filter performance.
Implementation Method 1
The series arm includes at least one series arm resonator, and the plurality of parallel arms each include at least one parallel arm resonator
Data Source
AI summary
A signal separation device is a duplexer in which a reception frequency band is located at higher frequencies than a transmission frequency band. A series arm of a ladder transmission filter includes a plurality of series arm resonators, and parallel arms respectively include parallel arm resonators. The parallel arm resonators include the parallel arm resonators having resonant frequencies lower than those of the series arm resonators and the parallel arm resonator that has a resonant frequency which is located within the reception frequency band and which is higher than the resonant frequency of the series arm resonators and that has a lower capacitance than the series arm resonators and the parallel arm resonators.