Multi-Channel SAW Filter Layout for Tunable COMB Frequency Response

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Solution Overview

Problem

Conventional SAW filters have limited frequency tuning range and fixed frequency response shape, resulting in crude filter properties such as rejection, insertion loss, and pass band shape.

Innovation Solution

The development of multi-channel SAW filter devices using a voltage-controlled tunable piezoelectric substrate with parallel input and output sub-transducers, each producing a unique COMB frequency response, allowing for tunable frequency responses and improved filter characteristics like flat passbands and steep rejection skirts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a single input transducer and single output transducer are used in conventional SAW filters, then the device structure is simple, but the frequency tuning range is limited and the frequency response shape is fixed

Engineering Contradiction:

Improvefrequency tuning rangeVSAvoidtransducer structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent divides each transducer into multiple sub-transducers (e.g., first and second input sub-transducers, first and second output sub-transducers). Each sub-transducer has a different number of fingers, creating multiple parallel channels with different frequency responses. This segmentation enables frequency tuning by selectively activating different sub-transducer combinations while maintaining a manageable overall structure.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If voltage controlled velocity tunable piezoelectric substrate is used to produce COMB frequency response, then the frequency tuning range is multiplied, but the filter properties become crude with poor rejection, insertion loss, and fixed pass band shape

Engineering Contradiction:

Improvefrequency tuning rangeVSAvoidfilter performance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies different finger configurations to different sub-transducers, creating localized variations in frequency response characteristics. Each sub-transducer pair forms a channel with specific frequency properties, allowing the overall filter to achieve both wide tuning range and controlled filter performance through selective channel combination.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent enables dynamic control of filter characteristics by applying different voltage levels to different sub-transducers. This allows real-time adjustment of the effective aperture and frequency response shape, transforming the fixed passband shape of conventional COMB filters into a dynamically adjustable parameter while maintaining wide frequency tuning capability.

Inventive Principle:

Principle #15Dynamics

3Reliability

If multiple sub-transducers are used to create parallel channels, then the frequency response becomes tunable with improved filter characteristics, but the device complexity increases

Engineering Contradiction:

Improvefilter characteristicsVSAvoidtransducer configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines multiple sub-transducers into unified input and output transducer assemblies with shared electrode structures. The sub-transducers are electrically connected in parallel configurations, merging their individual frequency responses into a composite filter response that achieves improved characteristics without proportionally increasing device complexity.

Inventive Principle:

Principle #5Merging (Combining)

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 enables a wider frequency range tuning with tunable filter shapes, achieving better sidelobe suppression and adjustable peak frequencies, enhancing filter performance.

Implementation Method 1

a voltage controlled velocity tunable piezoelectric substrate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

The input transducer converts an input electrical signal to a SAW, and the SAW propagates along the surface of the substrate to the output transducer. The output transducer then converts the SAW back into an output electrical signal.

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS7821360B2Multi-channel surface acoustic wave filter device with voltage controlled tunable frequency response

Publication Date: 2010.10.26 NORTHROP GRUMMAN SYSTEMS CORP

AI summary

A multi-channel surface acoustic wave (SAW) filter includes a voltage controlled velocity tunable piezoelectric substrate, an input transducer fabricated on the substrate, and an output transducer fabricated on the substrate. The input transducer further includes multiple input sub-transducers that are electrically and physically connected in parallel. The output transducer further includes multiple output sub-transducers that are electrically and physically connected in parallel. Corresponding pairs of input sub-transducers and output sub-transducers form multiple parallel channels for SAW propagation. The input transducer produces a voltage controlled tunable COMB frequency response that is combined with a voltage controlled tunable COMB frequency response produced by the output transducer to produce a SAW filter voltage controlled tunable frequency response. Further embodiments include a multi-channel SAW resonator, a SAW filter device connecting two novel SAW filters in series, and a SAW filter device connecting two novel SAW resonators in series.