Multiplexer Filter Topology for Wide Bandwidth and Steep Attenuation
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Solution Overview
Problem
Current multiplexers face challenges in achieving a wide pass band, small insertion loss, and steep attenuation characteristics at the end of the pass band, particularly with the increasing narrow gaps between frequency bands.
Innovation Solution
A filter design incorporating a series arm resonant circuit with an LC series resonant circuit and a parallel arm resonator, where the series arm resonant circuit lacks an anti-resonant frequency and has gentle resonance characteristics, combined with a parallel arm resonator that provides steep attenuation by sharp impedance fall near the resonant frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an elastic wave resonator is used in the series arm resonant circuit, then the filter can provide steep attenuation at the end of the pass band, but the pass band becomes narrow and insertion loss increases
Solution Approach 1:
The filter is divided into multiple resonant circuits with different functions: the series arm uses an LC series resonant circuit for wide bandwidth and low loss, while the parallel arm uses an elastic wave resonator for steep attenuation. This segmentation allows each part to optimize its specific function without compromising the overall performance.
Solution Approach 2:
Different regions of the filter are assigned different resonant circuit types based on their specific requirements. The series arm region uses LC circuits with gentle resonance characteristics suitable for wide bandwidth, while the parallel arm region uses elastic wave resonators with sharp impedance characteristics suitable for steep attenuation at the pass band edge.
2Adaptability or versatility
If an LC series resonant circuit is used in the series arm, then the pass band width increases and insertion loss decreases, but the attenuation characteristic at the end of the pass band becomes less steep
Solution Approach 1:
The filter merges two different resonant circuit types (LC series resonant circuit and elastic wave resonator) into a single system. The LC series resonant circuit provides wide bandwidth and low insertion loss, while the parallel-connected elastic wave resonator adds the steep attenuation characteristic, combining the advantages of both circuit types.
Solution Approach 2:
The parallel arm elastic wave resonator acts as an intermediary element that modifies the overall frequency characteristic of the filter. It introduces sharp impedance changes near its resonant frequency, which creates the steep attenuation characteristic at the pass band edge without significantly affecting the wide bandwidth provided by the series arm LC circuit.
3Adaptability or versatility
If the gap between frequency bands is narrowed to support more bands, then multi-band capability improves, but filter performance (pass band width, insertion loss, attenuation) deteriorates
Solution Approach 1:
The filter design allows for dynamic adjustment of resonant frequencies and impedance characteristics by selecting appropriate LC component values and elastic wave resonator parameters. This enables the filter to be optimized for different frequency band configurations, maintaining high performance even when bands are closely spaced.
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 enhances matching within a wide pass band, reduces insertion loss, and achieves a steep attenuation characteristic at the end of the pass band, resulting in a filter with improved performance for multiplexers.
Implementation Method 1
The series arm resonant circuit is an LC series resonant circuit in which a third inductor and a capacitor are connected in series with each other
Implementation Method 2
a parallel arm resonator in which one end is grounded
Data Source
AI summary
A filter includes a resonant circuit defining at least a portion of a signal path connected between a first terminal and a second terminal, an elastic wave resonator including one end that is grounded, a first inductor including one end connected to one end of the resonant circuit and another end connected to another end of the elastic wave resonator, and a second inductor including one end connected to another end of the resonant circuit and another end connected to the other end of the elastic wave resonator. The resonant circuit is an LC series resonant circuit in which a third inductor and first and second capacitors are connected in series with each other.