SAW Duplexer Resonator Layout for High Isolation and Low Loss
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Solution Overview
Problem
Mobile communications terminals face challenges in reducing size and weight while maintaining low loss and good out-of-band attenuation characteristics, particularly with the increasing complexity of RF front-end components, and existing duplexers struggle to improve isolation characteristics without increasing insertion loss.
Innovation Solution
A duplexer design incorporating a piezoelectric substrate with a transmitting filter and a receiving filter, featuring a ladder configuration with specific resonator arrangements and inductors to enhance attenuation characteristics, where the resonance frequency of the closest resonator is set lower than the transmission passband to improve signal attenuation in the vicinity of the passband.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of components in the RF front end is increased to meet multi-functional and multi-banded requirements, then the functionality and adaptability are improved, but the size and weight of the mobile communications terminal increase
Solution Approach 1:
The patent combines multiple filter functions (transmit filter and receive filter) into a single duplexer component. The duplexer integrates both filtering paths with different frequency passbands into one unified structure, reducing the total number of separate components while maintaining multi-functional capability.
Solution Approach 2:
The duplexer is designed to handle both transmission and reception functions simultaneously with different frequency passbands. By making the duplexer universal for both transmit and receive operations, the patent eliminates the need for separate filters for each function, thereby reducing overall device size and weight.
2Volume of stationary object
If a surface acoustic wave filter is used to reduce device size, then the volume is reduced, but the isolation characteristics and insertion loss performance deteriorate
Solution Approach 1:
The patent applies different design characteristics to different parts of the filter system. The transmit filter and receive filter have different frequency passbands and are optimized for their specific functions. The receive filter is specifically designed with resonators positioned to provide strong attenuation in the transmit frequency band, while the transmit filter is optimized for low insertion loss in its passband.
Solution Approach 2:
The patent changes the resonance frequency parameters of the receive filter's resonators to be lower than the transmit passband frequency. This parameter adjustment creates a frequency separation that improves isolation characteristics while maintaining compact size through surface acoustic wave technology.
3Reliability
If the resonance frequency of receive filter resonators is lowered to improve attenuation in the transmit band, then the isolation characteristics are improved, but the passband of the receive filter may be affected
Solution Approach 1:
The patent segments the filter design into distinct transmit and receive paths with independent optimization. The receive filter's resonators are positioned and frequency-tuned to provide attenuation only in the transmit frequency band, while the receive passband remains unaffected. This segmentation allows each filter to be optimized for its specific function without compromising the other.
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 duplexer achieves high attenuation characteristics in frequency ranges outside the passband, particularly in the lower vicinity of the transmission passband, while maintaining small size and reducing signal loss, thereby supporting compact and high-quality communications equipment.
Implementation Method 1
a piezoelectric substrate, a transmitting filter (F1), and a receiving filter (F2)
Implementation Method 2
the duplexer is recently manufactured by using a surface acoustic wave filter
Implementation Method 3
a resonator at a first stage of a transmitting filter formed of a ladder filter is configured as a parallel resonator
Data Source
AI summary
A duplexer includes a piezoelectric substrate, a transmitting filter, and a receiving filter. A transmitting filter includes a ladder filter having a first resonator group which has one or more resonators in one or more series arms and one or more resonators in one or more parallel arms. A receiving filter has a passband higher than that of the transmitting filter, and includes a second resonator group which has one or more resonators in one or more series arms and one or more resonators in one or more parallel arms. A node connects both the transmitting filter and the receiving filter. The receive-side closest resonator closest to the node in the parallel arm is closer to the node than a resonator which is closest to the node in the series arm, and a resonance frequency of the receive-side closest resonator is lower than the passband of the transmitting filter.