Acoustic Wave Filter Multiplexer for Close-Band Isolation
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Solution Overview
Problem
Existing multiband and multimode front-end circuits face challenges in achieving low insertion loss and high isolation while maintaining a compact size, particularly when handling radio-frequency signals with small frequency gaps.
Innovation Solution
The implementation of an acoustic wave filter circuit formed on a piezoelectric substrate, utilizing a multiplexer with co-band filters and switches to manage multiple bands, including a power amplifier and impedance matching circuit, ensures isolation between bands with non-overlapping frequency ranges and supports frequency division and time division duplex communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If individual filters are used for each band to secure sufficient isolation between bands with small frequency gaps, then isolation between bands is improved, but the size of the front-end circuit increases
Solution Approach 1:
The patent combines multiple filter functions into a single acoustic wave filter circuit that handles multiple bands (e.g., Band 13 and Band 14) with a unified structure. The filter uses a single substrate with piezoelectric properties and integrates multiple resonators and transmission lines to achieve band separation without requiring separate filter modules for each band, thereby reducing overall circuit size while maintaining isolation performance.
Solution Approach 2:
The acoustic wave filter circuit is designed to perform multiple functions simultaneously - filtering signals across different frequency bands (uplink and downlink for multiple bands) using a single device. The filter structure supports both FDD and TDD modes and can handle multiple bands through careful design of resonator frequencies and coupling structures, eliminating the need for multiple dedicated filters.
2Reliability
If multiple filters are used to handle multiple bands, then band isolation is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple filter functions into a single integrated acoustic wave filter circuit. The design combines multiple resonators, transmission lines, and coupling structures into one unified device that can filter multiple bands simultaneously, reducing the number of discrete components and simplifying the overall circuit architecture.
Solution Approach 2:
Within the unified filter structure, the patent uses segmentation by creating distinct resonator units and transmission line sections that can be independently designed for specific frequency responses. Each resonator group handles specific bands, but they work together within a single integrated structure rather than as separate filter modules.
3Area of stationary object
If a compact filter design is used to reduce circuit size, then area is reduced, but achieving high isolation between close bands becomes difficult
Solution Approach 1:
The patent applies local quality by designing specific regions within the filter with different characteristics - using different resonator configurations, coupling coefficients, and transmission line impedances in different parts of the filter to optimize isolation for specific band combinations. The filter structure has locally optimized sections that target specific frequency gaps while maintaining overall compactness.
Solution Approach 2:
The patent achieves high isolation in a compact design by carefully adjusting parameters such as resonator frequencies, coupling coefficients, and transmission line lengths. By optimizing these parameters, the filter creates deep attenuation notches at specific frequencies to block adjacent bands while maintaining a small physical footprint through efficient use of the acoustic wave propagation paths.
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 configuration allows for a compact design that maintains high isolation between bands with small frequency gaps, reducing signal distortion and enhancing signal processing efficiency.
Implementation Method 1
The acoustic wave filter circuit is formed in or on a first substrate having piezoelectric properties
Implementation Method 2
acoustic wave filter circuit formed in or on a first substrate having piezoelectric properties
Data Source
AI summary
A frequency division duplex (FDD) first band includes a first downlink operating band and a first uplink operating band. An FDD second band includes a second downlink operating band and a second uplink operating band. In the FDD first band and the FDD second band, (1) the first downlink operating band, second downlink operating band, first uplink operating band, and second uplink operating band are positioned in order from lowest to highest frequency. The frequency range of the first uplink operating band and that of the second uplink operating band do not overlap each other. A filter is formed in or on a first substrate having piezoelectric properties and has a pass band including the first and second uplink operating bands.