RF Filter Module Resonator Layout for Second Harmonic Suppression
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Solution Overview
Problem
Current RF filter modules face linearity issues, particularly in generating second harmonic signals, which are exacerbated by the stringent requirements of 5G NR, while also needing to be compact and cost-effective.
Innovation Solution
Incorporating a resonating structure with anti-series or anti-parallel connected resonators on a c-axis oriented piezoelectric film, where the polarity directions of the resonators oppose each other, to improve linearity response by suppressing second harmonic signals, and optionally including additional acoustic filters for specific frequency detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional filter designs are used, then the filter module is simple and cost-effective, but the linearity response deteriorates due to second harmonic signal generation
Solution Approach 1:
The filter structure is segmented into multiple resonators (first resonator, second resonator, third resonator) with different connectivity configurations. Each resonator handles specific frequency components, with the first resonator connected to the input node, the second resonator connected to both input and output nodes, and the third resonator connected to the output node. This segmentation allows selective suppression of second harmonic signals while maintaining fundamental signal transmission.
Solution Approach 2:
Different resonators are assigned different connectivity qualities and configurations tailored to their specific functions. The first resonator has a specific connectivity pattern optimized for fundamental signal handling, while the second and third resonators have different connectivity patterns optimized for harmonic suppression. This local differentiation of resonator properties enables targeted linearity improvement without uniformly complicating the entire filter structure.
2Reliability
If additional resonators and harmonic signal paths are added to suppress second harmonic signals, then linearity response improves, but device complexity increases
Solution Approach 1:
The resonators are designed to perform multiple functions simultaneously. The second resonator, for example, is connected to both the input node and output node, allowing it to influence both the fundamental signal path and the second harmonic signal path. This multi-functionality enables the filter to suppress second harmonic signals while maintaining fundamental signal transmission using the same resonating structures, rather than requiring separate dedicated components for each function.
Solution Approach 2:
The harmonic signal path is merged with the fundamental signal path through strategic node sharing. The second resonator connects both input and output nodes, creating a shared pathway that allows a single resonating structure to affect both signal types. This merging reduces the need for completely separate harmonic suppression circuits, thereby limiting the increase in device complexity while still achieving improved linearity response.
3Reliability
If resonators are configured with opposite polarity directions, then second harmonic signals are suppressed improving linearity, but manufacturing precision requirements increase
Solution Approach 1:
The resonators are configured with asymmetric polarity directions relative to each other. The first resonator has a polarity direction from first electrode to second electrode, while the second resonator has an opposite polarity direction from third electrode to fourth electrode. This asymmetric configuration is deliberately designed to create destructive interference for second harmonic signals while preserving fundamental signal transmission. The asymmetry, while requiring precise manufacturing, provides a clear design target that can be achieved through standard fabrication processes.
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 significantly improves linearity response by suppressing second harmonic signals, achieving a 50 dB improvement over conventional designs, while maintaining a compact and cost-effective filter module suitable for 5G NR applications.
Implementation Method 1
a plurality of resonators that are electrically connected to each other in anti-series or anti-parallel and disposed on a piezoelectric film
Implementation Method 2
at least one resonating structure configured to improve a linearity response of the filter module
Data Source
AI summary
Aspects and embodiments disclosed herein include filter module comprising an input port to receive a radio frequency signal, a first output port connected to an antenna, a filter disposed along a fundamental signal path from the input port to the first output port, and a second output port to output a harmonic signal generated in response to the RF signal, the second output port being electrically connected to a node on the fundamental signal path via a harmonic signal path including a resonating structure configured to improve a linearity response of the filter module, the resonating structure including resonators electrically connected to each other in anti-series or anti-parallel and disposed on a piezoelectric film, a polarity direction of a first half of the resonators opposite to a polarity direction of a second half of the resonators when a voltage is applied across the piezoelectric film.