FBAR Filter With Integrated Lamb Wave Loop for RF Isolation
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Solution Overview
Problem
Acoustic wave filters, particularly film bulk acoustic resonator (FBAR) filters, face challenges in achieving effective transmit/receive isolation and attenuation due to the large physical footprint and external implementation of LC circuits used in loop cancellation circuits, which limits their integration and efficiency.
Innovation Solution
The integration of a Lamb wave loop circuit with FBAR filters, utilizing a piezoelectric layer with free edges to suppress or scatter reflections, allows for improved isolation and attenuation characteristics within a smaller physical footprint, combining features of SAW and BAW resonators to enhance RF signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external LC circuits are used for loop cancellation, then transmit/receive isolation and attenuation are improved, but the physical footprint increases and integration is limited
Solution Approach 1:
The patent merges the loop cancellation function with the FBAR filter structure by integrating a Lamb wave resonator directly into the filter circuit. This consolidation eliminates the need for external LC circuits, achieving the desired transmit/receive isolation while significantly reducing the physical footprint through monolithic integration on the same substrate.
Solution Approach 2:
The patent replaces the traditional electrical LC circuit with a mechanical acoustic resonance system based on Lamb wave resonators. This substitution enables loop cancellation functionality to be achieved through acoustic wave interference rather than electrical components, allowing for compact integration while maintaining isolation performance.
2Area of stationary object
If Lamb wave resonator is integrated with FBAR filter, then isolation and attenuation are improved within smaller footprint, but device complexity increases
Solution Approach 1:
The Lamb wave resonator serves multiple functions simultaneously: it acts as both the cancellation element for loop suppression and as a functional resonator within the filter structure. This multi-functionality reduces the need for separate components, thereby managing device complexity while achieving compact integration and improved isolation performance.
Solution Approach 2:
The patent utilizes changes in acoustic wave parameters (frequency, phase, propagation mode) to achieve cancellation functionality. By controlling the Lamb wave resonator to generate anti-phase signals at specific frequencies, the system achieves loop cancellation through parameter manipulation rather than complex circuit topology, simplifying the overall device 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
The Lamb wave loop circuit enhances transmit/receive isolation and attenuation, offering a cost-effective and efficient solution by reducing power consumption and manufacturing costs, while overcoming limitations of SAW and BAW resonators, and improving the frequency range capabilities of acoustic wave filters.
Implementation Method 1
an edge of the piezoelectric layer configured to one of suppress or scatter reflections of acoustic waves generated by the interdigital transducer electrode from the edge of the piezoelectric layer
Implementation Method 2
a Lamb wave resonator having a piezoelectric layer and an interdigital transducer electrode disposed on the piezoelectric layer
Data Source
AI summary
An acoustic wave device includes 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 resonator having a piezoelectric layer and an interdigital transducer electrode disposed on the piezoelectric layer. The piezoelectric layer includes free edges. An edge of the piezoelectric layer is configured to one of suppress or scatter reflections of acoustic waves generated by the interdigital transducer electrode from the edge of the piezoelectric layer.