Phase-Weighted Band-Pass Filter for Steep Edges and Low Loss
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Solution Overview
Problem
Existing broadband filters with FAN transducers face limitations in achieving high edge steepness without increasing transducer length, which also leads to higher insertion loss and temperature drift issues.
Innovation Solution
The implementation of phase weighting in partial acoustic tracks, where cells of different lengths within each track cause varying phase rotations, allowing for a higher edge steepness and improved filter selection, even with shorter transducer lengths, by adjusting the distribution of excitation and reflection centers across the transducer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the transducer length is increased to achieve higher edge steepness, then the edge steepness is improved, but the insertion loss increases and temperature drift worsens
Solution Approach 1:
The transducer is divided into multiple partial tracks, each with different phase weightings. This segmentation allows independent optimization of each partial track's contribution to the overall frequency response, enabling high edge steepness through constructive interference at the band edges without requiring increased transducer length.
Solution Approach 2:
Different phase weightings are applied to different partial tracks based on their specific frequency characteristics. The partial tracks with extreme center frequencies (lowest and highest) are given different phase weightings to optimize the edge steepness at respective band edges, while intermediate partial tracks are optimized for their local frequency regions.
2Manufacturing precision
If the transducer length is increased to achieve higher edge steepness, then the edge steepness is improved, but the temperature drift increases
Solution Approach 1:
By segmenting the transducer into partial tracks with independent phase control, the system achieves high edge steepness through phase interference effects rather than increased physical length. This reduces the overall transducer length and associated temperature drift while maintaining spectral selectivity.
Solution Approach 2:
The phase weightings of partial tracks are adjusted as a design parameter to optimize edge steepness. By changing the phase weighting parameters rather than physical dimensions, the system achieves high selectivity with a compact structure that has reduced temperature sensitivity.
3Loss of energy
If the transducer length is reduced to lower insertion loss, then the insertion loss is improved, but the edge steepness decreases
Solution Approach 1:
The transducer is segmented into partial tracks that are shorter than a conventional transducer would need to be. Through phase weighting, these shorter partial tracks collectively achieve high edge steepness via constructive and destructive interference, maintaining spectral selectivity without requiring long physical dimensions.
Solution Approach 2:
Instead of achieving edge steepness through increased length in one dimension, the invention uses phase weighting to create spectral selectivity in the frequency domain. This dimensional transformation allows compact physical size while maintaining high edge steepness through phase interference effects.
4Stability of the object's composition
If the transducer length is reduced to minimize temperature drift, then the temperature stability is improved, but the edge steepness decreases
Solution Approach 1:
Segmenting the transducer into phase-weighted partial tracks enables high edge steepness with reduced physical length. This segmentation approach decouples the relationship between physical size and spectral selectivity, allowing compact design with improved temperature stability while maintaining high edge steepness through phase interference.
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 approach enables the creation of broadband band pass filters with enhanced edge steepness and reduced insertion loss, while maintaining a compact design and minimizing temperature-related performance degradation.
Implementation Method 1
The transducers each may have two busbars, to which the electrode fingers are connected. The electrode fingers connected to different electric potentials are interdigitated. This structure is arranged on a piezoelectric substrate and is used for the electroacoustic transformation of a (high-frequency) electronic signal into an acoustic wave and vice versa.
Implementation Method 2
The directional beaming comes about thanks to the constructive superpositioning of the excited and the reflected wave in one direction and destructive superpositioning of the excited and the reflected wave in the opposite direction.
Implementation Method 3
As it travels through a cell, a wave undergoes a phase rotation, which is proportional to the cell length, normalized to the wavelength. In one embodiment, partial tracks are each phase-weighted, i.e., they each have cells of different length. By phase weighting in a partial track is meant here that a wave with a wavelength corresponding to the center frequency undergoes different phase rotations as it travels through different cells of the partial track.
Data Source
AI summary
A band pass filter includes partial filters, each of which has a pass band. Pass bands of different ones of the partial filters have center frequencies that are different. A partial filter with a lowest center frequency has a pass band with a first low-frequency edge and a first high-frequency edge. The first low-frequency edge is steeper than first high-frequency edge. A partial filter with a highest center frequency has a pass band with a second low-frequency edge and a second high-frequency edge. The second high-frequency edge is steeper than the second low-frequency edge.