DMS Filter Sub-Transducer Spacing for Steeper Upper Edge
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Solution Overview
Problem
DMS filters used in modern communication standards face challenges in achieving high selectivity and bandwidth due to their flat passband edge and minimal selectivity, which is exacerbated by the use of high-coupling piezoelectric substrate materials leading to increased pole-zeroing distance and reduced edge steepness.
Innovation Solution
The DMS filter design involves alternately arranging first and second transducers on a piezoelectric substrate between reflectors, with the transducers being symmetrically divided into sub-transducers spaced less than half a wavelength apart, creating a zero in the transfer function to steepen the right edge without compromising other filter properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If DMS filter is used for broadband filtering, then bandwidth is increased, but edge steepness deteriorates due to flat passband top edge
Solution Approach 1:
The transducers are divided into sub-transducers (first and second sub-transducers) that are spaced apart by a distance D between 0.25λ and 0.5λ. This segmentation creates additional transmission zeros that steepen the passband edge while preserving the broadband characteristics of the DMS filter structure.
2Object-generated harmful factors
If high-coupling piezoelectric substrate materials are used, then coupling is improved, but pole-zeroing distance increases leading to reduced selectivity
Solution Approach 1:
The invention introduces a spatial dimension parameter D (distance between sub-transducers) that is optimized to be between 0.25λ and 0.5λ. This dimensional adjustment creates transmission zeros at specific frequencies, enabling steep edge rolloff and improved selectivity independent of the substrate coupling characteristics.
3Manufacturing precision
If capacitor is connected in parallel to single-gate resonators, then pole-zeroing distance is reduced, but insertion loss increases
Solution Approach 1:
The invention replaces the electrical compensation approach (using parallel capacitors) with a mechanical/spatial arrangement of sub-transducers spaced by distance D. This spatial configuration inherently creates the necessary transmission zeros through interference effects, eliminating the need for additional capacitive elements and their associated losses.
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 design enhances selectivity and bandwidth by steepening the upper passband edge while maintaining filter performance, allowing the DMS filter to meet the requirements of modern communication standards like LTE without additional effort or compensation measures.
Implementation Method 1
high-coupling piezoelectric substrate materials must be used
Implementation Method 2
acoustic wave in the DMS filter
Data Source
AI summary
In an arrangement having a DMS filter, it is provided to symmetrically divide at least one of the transducers (W) of the DMS filter (DMS) into two sub-transducers (T,T′) electrically connected in parallel and to shift them apart from each other by an amount of at least a half wavelength. This results in the signals of the two sub-transducers canceling each other out at a frequency in a stopband and thereby generating an attenuation pole in the upper blocking region.