Extractor Inductance Gradient for Filter Isolation
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Solution Overview
Problem
In extractors with a combination of band pass filters and band elimination filters, harmonic waves generated by the band pass filter degrade isolation between the filters in frequency bands higher than the stop band of the band elimination filter, leading to increased insertion loss.
Innovation Solution
The extractor design includes a band elimination filter connected between a common terminal and a first input-output terminal, with a band pass filter connected between the common terminal and a second input-output terminal, featuring series arm resonators, parallel arm resonators, and inductors. The inductance values of inductors nearest to the common terminal are smaller than those further away, optimizing impedance and reducing reflection coefficients in higher frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a band pass filter and band elimination filter are connected to a common terminal, then multiple frequency bands can be handled by a single antenna, but harmonic waves from the band pass filter degrade isolation and increase insertion loss in the band elimination filter
Solution Approach 1:
The patent applies local quality by making the inductance values of inductors non-uniform in the band pass filter circuit. Specifically, inductors closer to the common terminal have smaller inductance values while those farther away have larger inductance values. This localized variation in inductance optimizes the impedance characteristics at different positions, suppressing harmonic wave generation and improving isolation between the band pass filter and band elimination filter.
Solution Approach 2:
The patent changes the inductance parameter values of the inductors in the band pass filter to resolve the contradiction. By setting specific inductance values where L1 < L3 (comparing inductors at different positions), the filter characteristics are optimized to reduce harmonic waves in frequency bands higher than the stop band, thereby improving isolation without sacrificing multi-frequency band handling capability.
2Reliability
If inductance values of inductors are made non-uniform with smaller values near the common terminal, then isolation between filters is improved, but device complexity increases
Solution Approach 1:
The patent resolves this contradiction by systematically changing the inductance parameters of existing inductors in the band pass filter rather than adding new components. The inductance values are assigned based on their position relative to the common terminal, creating a gradient structure that improves isolation while maintaining the original filter topology and not significantly increasing device 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
This configuration reduces the insertion loss of the band elimination filter in frequency bands higher than its stop band, improving signal quality and isolation between filters.
Implementation Method 1
series arm resonators that include an acoustic wave resonator and that are disposed on a series arm that connects the common terminal and the second input-output terminal to each other
Implementation Method 2
a band pass filter that is connected between the common terminal and the second input-output terminal and that has a pass band equal or substantially equal to a second frequency band
Data Source
AI summary
An extractor includes a band elimination filter that is connected between a common terminal and a first input-output terminal and that has a stop band equal or substantially equal to a first frequency band, and a band pass filter that is connected between the common terminal and a second input-output terminal and that has a pass band equal or substantially equal to a second frequency band that overlaps the first frequency band. The band pass filter includes, series arm resonators, three or more parallel arm resonators, and three or more inductors that are connected between the ground and the parallel arm resonators. The L value of a first inductor that is connected and nearest to the common terminal is smaller than the L value of a third inductor, and the L value of a second inductor that is connected and second-nearest to the common terminal is smaller than the L value of the third inductor.