Lamb Wave Loop Circuit for Acoustic Filter Isolation
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Solution Overview
Problem
Current acoustic wave filters, such as SAW and BAW filters, face challenges in achieving effective transmit/receive isolation and attenuation due to their large physical footprint and external implementation of LC circuits, which limits their integration and efficiency in radio frequency systems.
Innovation Solution
The integration of a Lamb wave loop circuit with bulk acoustic wave filters, utilizing an aluminum nitride Lamb wave element, which generates an anti-phase signal to cancel target frequencies, enhancing isolation and attenuation within a smaller physical footprint and improving integration with CMOS process technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional SAW and BAW filters are used, then filtering function is achieved, but transmit/receive isolation and attenuation are insufficient
Solution Approach 1:
The patent combines the filter and loop circuit into a single integrated device, where the loop circuit is formed using the same piezoelectric substrate and IDT structures as the filter. This merging eliminates the need for separate external LC circuits, improving transmit/receive isolation while reducing the overall physical footprint.
Solution Approach 2:
The invention uses aluminum nitride piezoelectric material for both the filter and loop circuit structures, creating a composite acoustic wave device. This composite approach enables both filtering and signal cancellation functions within the same material system, enhancing isolation performance without increasing size.
2Reliability
If external LC circuits are implemented, then isolation improvement is achieved, but integration with CMOS process is limited
Solution Approach 1:
The patent replaces traditional electrical LC circuits with acoustic wave-based loop circuit structures made from piezoelectric materials. This substitution allows the loop circuit to be fabricated using the same CMOS-compatible piezoelectric deposition processes as the main filter, significantly improving integration and reducing device complexity.
Solution Approach 2:
The aluminum nitride piezoelectric substrate serves multiple functions: it acts as the acoustic waveguide for the filter, provides the piezoelectric coupling for the IDTs, and forms the structural basis for the loop circuit. This multi-functionality enables both filtering and isolation enhancement within a single integrated structure compatible with CMOS manufacturing.
3Reliability
If larger physical footprint is used, then isolation performance is improved, but power consumption increases
Solution Approach 1:
The loop circuit operates by generating acoustic waves at the target frequency that interfere destructively with unwanted signals. This mechanical vibration-based approach uses the inherent acoustic resonance of the piezoelectric structure to achieve signal cancellation without requiring additional power-hungry electronic amplification stages, thus improving isolation while maintaining low power consumption.
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 Lamb wave loop circuit effectively improves transmit/receive isolation and attenuation in acoustic wave filters, reducing power consumption and manufacturing costs while enabling more efficient integration with other circuits, thus enhancing the performance of radio frequency systems.
Implementation Method 1
The Lamb wave element can include an interdigital transducer electrode on a piezoelectric layer
Implementation Method 2
The Lamb wave element can include an interdigital transducer electrode on a piezoelectric layer, in which the interdigital transducer electrode has free edges
Data Source
AI summary
Aspects of this disclosure relate to an acoustic wave filter configured to filter a radio frequency signal and a loop circuit coupled to the acoustic wave filter. The loop circuit is configured to generate an anti-phase signal to a target signal at a particular frequency. The loop circuit includes a Lamb wave element. Related radio frequency modules and wireless communication devices are disclosed.