Hybrid Band-Pass Branching Filter for Sharp Cutoff Separation
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Solution Overview
Problem
Conventional band-pass filters struggle to provide an insertion loss characteristic that abruptly changes near the cut-off frequency, making it difficult to separate signals in closely spaced frequency bands effectively, with LC filters lacking this capability and acoustic wave filters not offering a wide passband.
Innovation Solution
A band-pass filter configuration using an LC resonant circuit and an acoustic wave resonator section, where the resonant frequency is within the passband and anti-resonant frequencies are outside, allowing for abrupt insertion loss changes near the cut-off frequencies, and a branching filter design incorporating these band-pass filters to separate signals in close frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If LC filters are used, then the device structure is simple, but the insertion loss characteristic cannot change abruptly near the cut-off frequency
Solution Approach 1:
The patent combines LC filters and acoustic wave filters into a hybrid filter structure. The LC filter provides the basic frequency selection with simple structure, while the acoustic wave filter component introduces abrupt insertion loss changes near the cut-off frequency through its resonant characteristics, thereby resolving the contradiction between structural simplicity and performance reliability.
Solution Approach 2:
The patent uses a composite filtering approach by integrating two different filter technologies (LC and acoustic wave) with distinct operational characteristics. This composite structure allows the filter to simultaneously achieve the structural advantages of LC filters and the sharp cutoff characteristics of acoustic wave filters, effectively addressing the technical contradiction.
2Reliability
If acoustic wave filters are used, then the insertion loss characteristic changes abruptly near the cut-off frequency, but the passband width is limited
Solution Approach 1:
The hybrid filter structure merges the wide passband capability of LC filters with the sharp cutoff characteristic of acoustic wave filters. The LC filter portion handles the wide frequency range requirement, while the acoustic wave filter portion provides the abrupt insertion loss change, thus resolving the contradiction between passband width and cutoff sharpness.
3Measurement precision
If a branching filter separates closely spaced frequency bands, then signal separation effectiveness improves, but filter design complexity increases
Solution Approach 1:
The patent applies the hybrid LC-acoustic wave filter structure to the branching filter design, where each band-pass filter in the branching configuration benefits from the combined advantages of both filter types. This approach achieves effective separation of closely spaced frequency bands while avoiding the excessive complexity that would result from using only acoustic wave filters or multiple LC filters.
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 provides a branching filter that effectively separates signals in closely spaced frequency bands with an abrupt insertion loss characteristic, achieving miniaturization and improved performance compared to traditional LC filters.
Implementation Method 1
The resonant circuit section includes at least one acoustic wave resonator provided in a path leading from the first port to the second port. The acoustic wave elements include surface acoustic wave elements using surface acoustic waves, and bulk acoustic wave elements using bulk acoustic waves.
Implementation Method 2
The acoustic wave elements include surface acoustic wave elements using surface acoustic waves
Implementation Method 3
The acoustic wave elements include bulk acoustic wave elements using bulk acoustic waves
Implementation Method 4
an LC resonant circuit and a resonant circuit section provided in series between the first port and the second port
Data Source
AI summary
A branching filter includes a first band-pass filter provided between a common port and a first signal port, and a second band-pass filter provided between the common port and a second signal port. The first band-pass filter includes a first LC resonant circuit and a first resonant circuit section. The first resonant circuit section includes a first acoustic wave resonator. The second band-pass filter includes a second LC resonant circuit and a second resonant circuit section. The second resonant circuit section includes a second acoustic wave resonator and an inductor connected in parallel.