Multi-Path Acoustic Wave Filter for Wideband RF Rejection
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Solution Overview
Problem
Current filter designs face challenges in achieving wide bandwidth and high out-of-band rejection, particularly in 5G frequency bands, due to limitations in electromechanical coupling coefficients of bulk acoustic wave (BAW) resonators, leading to high insertion loss and difficulty in meeting stringent intermodulation distortion (IMD) specifications.
Innovation Solution
A multi-path filter design incorporating a band pass section and an extractor section with series and shunt acoustic wave resonators, along with a phase shifter, which combines impedance responses to create a wide passband and significant rejection, overcoming the limitations of BAW resonators by achieving impedance cancellation outside the passband.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional acoustic wave ladder filters are used, then the filter structure is simple, but the bandwidth is limited and out-of-band rejection is insufficient
Solution Approach 1:
The filter is divided into multiple independent signal paths (first signal path with series resonator, second signal path with shunt resonator and phase shifter), each handling specific frequency ranges. This segmentation enables the filter to achieve wide bandwidth (at least 800 MHz) and high out-of-band rejection (at least 50 dB) by combining the frequency responses of different paths, while maintaining a manageable structure through modular design
Solution Approach 2:
The invention introduces a new dimension to the traditional ladder filter by adding multiple signal paths with different topologies (series and shunt configurations) and incorporating phase shifters. This multi-dimensional approach allows the filter to achieve superior performance in both bandwidth and rejection characteristics that cannot be obtained with conventional single-path ladder structures
2Object-affected harmful factors
If more acoustic wave resonators are added to increase rejection, then out-of-band rejection improves, but insertion loss increases
Solution Approach 1:
Phase shifters are introduced as intermediary components in the second signal path to control the phase relationship between different resonators. This allows for precise impedance cancellation at specific frequency bands (achieving at least 50 dB rejection at Wi-Fi frequencies) while maintaining low insertion loss in the passband, as the phase shifters enable constructive interference for desired signals and destructive interference for unwanted signals without requiring excessive resonators
Solution Approach 2:
The invention changes the electrical parameters (impedance, phase) of the signal paths dynamically across different frequency ranges. By adjusting the phase shift and impedance values in different paths, the filter achieves high rejection at specific out-of-band frequencies while maintaining low insertion loss in the passband, optimizing the trade-off between rejection and loss
3Volume of moving object
If BAW resonators with limited electromechanical coupling coefficients are used, then the filter is compact, but the bandwidth is constrained
Solution Approach 1:
The invention merges multiple signal paths with different resonator configurations (series and shunt) to achieve wide bandwidth performance. By combining the frequency responses of these paths and using impedance cancellation techniques, the filter achieves a bandwidth of at least 800 MHz (20% of center frequency) while maintaining a compact form factor suitable for 5G applications, overcoming the bandwidth limitations of individual BAW resonators
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 multi-path filter design provides a wider passband and improved rejection at frequencies where traditional ladder designs struggle, such as in 5G Wi-Fi and high band frequencies, while maintaining competitive insertion loss and reducing the number of resonators needed.
Implementation Method 1
In BAW resonators, acoustic waves propagate in a bulk of a piezoelectric layer
Implementation Method 2
An acoustic wave filter can include a plurality of acoustic resonators arranged to filter a radio frequency signal
Implementation Method 3
The multi-path filter can have a passband formed by at least a combined impedance response of the first signal path and the second signal path
Implementation Method 4
Impedances of the first signal path and the second signal path can cancel each other outside of the passband to form rejections
Implementation Method 5
The phase shifter can include a transmission line and a capacitor
Data Source
AI summary
Aspects of this disclosure relate to a multi-path filter for filtering a radio frequency signal. The multi-path filter includes two signal paths from a node to an output port. The first signal path includes a series acoustic wave resonator. The second signal path includes a shunt acoustic wave resonator and a phase shifter. Related multiplexers, radio frequency modules, radio frequency systems, wireless communication devices, and methods are disclosed.