Capacitively-coupled resonator for improvement in upper band edge steepness
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Solution Overview
Problem
Current radio frequency (RF) filters face challenges in achieving improved steepness at the upper band edge without increasing the number of stages or die size, which affects their performance in communications systems.
Innovation Solution
The implementation of a filter device that includes a series connection of bulk acoustic resonators with a capacitor connected between ground and a node between the resonators, creating an additional pole at the upper band edge, thereby enhancing the steepness of the high edge passband without increasing the filter's complexity or size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of stages or die size is increased to improve upper band edge steepness, then the filter performance is enhanced, but the device complexity and size increase
Solution Approach 1:
The patent changes the electrical parameters of the existing filter stages by introducing capacitive coupling between series-connected bulk acoustic resonators. This modifies the pole-zero distribution in the s-plane, specifically creating an additional pole near the jω axis that enhances the upper band edge steepness without requiring additional resonator stages.
Solution Approach 2:
The patent introduces capacitive coupling as an intermediary mechanism between existing resonators. This capacitive coupling acts as a mediator that creates additional poles and modifies the frequency response characteristics, achieving improved steepness without directly adding more resonator stages.
2Manufacturing precision
If the number of stages or die size is increased to improve upper band edge steepness, then the filter performance is enhanced, but the die size increases
Solution Approach 1:
The patent achieves improved upper band edge steepness by modifying the electrical parameters through capacitive coupling rather than adding physical resonator stages. This parameter-based approach allows achieving better frequency selectivity within the existing die area, avoiding the need to increase die size.
3Manufacturing precision
If additional poles are added to improve upper band edge steepness, then the filter selectivity is enhanced, but the device complexity increases
Solution Approach 1:
The patent uses capacitive coupling as an intermediary to generate additional poles in the transfer function. This approach creates the necessary poles for improved selectivity through electrical coupling rather than additional mechanical resonator structures, simplifying the overall device architecture.
Solution Approach 2:
The patent achieves enhanced frequency selectivity by changing the electrical parameters of the filter through capacitive coupling. This modifies the pole locations in the s-plane to provide steeper roll-off characteristics without requiring a more complex physical structure.
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 improves the filter's ability to maintain resonant frequency over a wider range of loads and stresses, resulting in a more robust and stable frequency response without increasing the number of stages or die size, thus enhancing system performance.
Implementation Method 1
each of the first and second bulk acoustic resonators comprising a piezoelectric layer; and an interdigital transducer (IDT) having a plurality of interleaved fingers at a surface of the piezoelectric layer; and a capacitor connected between ground and a node between the first bulk acoustic resonator and the second bulk acoustic resonator. In this aspect, the piezoelectric layer and the IDT are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the piezoelectric layer.
Implementation Method 2
a first bulk acoustic resonator and a second bulk acoustic resonator connected in series between the first port and the second port
Data Source
AI summary
A filter is provided that includes resonators connected in series between first and second ports. Each of the resonators includes a piezoelectric layer; and an interdigital transducer (IDT) having a plurality of interleaved fingers at a surface of the piezoelectric layer. The piezoelectric layer and the IDT are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the piezoelectric layer. The filter includes a capacitor connected between ground and a node between the first bulk acoustic resonator and the second bulk acoustic resonator.