Acoustic Wave Multiplexer Trap Circuit for Low-Loss H2 Suppression
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Solution Overview
Problem
Radio frequency systems face challenges in suppressing harmonic distortion and meeting stringent system level linearity specifications, particularly with bulk acoustic wave filters, where second-order harmonic emissions (H2) are difficult to reduce below -90 dBc using existing techniques.
Innovation Solution
The implementation of an acoustic assisted trap circuit within a multiplexer, which includes a first acoustic wave filter and a second acoustic wave filter with an impedance network, configured to trap harmonics, using an inductor and acoustic wave resonators, effectively reducing H2 emissions by providing a trap for harmonics associated with the first filter, thereby achieving less than -90 dBc.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional filtering techniques are used to suppress harmonic distortion, then the system can maintain basic linearity, but it cannot achieve the stringent specification of less than -90 dBc for second-order harmonic emissions
Solution Approach 1:
The patent converts the harmful harmonic distortion into a beneficial effect by using the harmonic frequency itself as the target for the trap circuit. The acoustic wave resonator is specifically tuned to resonate at the harmonic frequency (e.g., 2f0), creating a high-impedance path that selectively traps and suppresses the harmonic while passing the fundamental frequency unchanged. This transforms the problematic harmonic frequency into the precise target for suppression.
Solution Approach 2:
The patent introduces an intermediary acoustic wave resonator coupled with an impedance network between the bulk acoustic wave filter and the output. This intermediary component acts as a mediator that selectively interacts with the harmonic frequency generated by the BAW filter, providing a controlled impedance path that traps the harmonic without affecting the fundamental signal. The resonator serves as a bridge that separates the fundamental and harmonic frequencies through its resonant properties.
2Object-generated harmful factors
If additional trap circuits or surface mount devices are added to suppress harmonics, then harmonic suppression improves, but device complexity and area consumption increase
Solution Approach 1:
The patent merges the trap circuit functionality directly into the existing multiplexer structure by integrating the acoustic wave resonator and impedance network with the BAW filter. Instead of adding separate surface mount devices or independent trap circuits, the solution combines multiple functions (filtering and harmonic trapping) into a single integrated acoustic wave device, reducing overall device complexity and component count.
Solution Approach 2:
The acoustic wave resonator serves multiple functions simultaneously: it acts as both a filtering element and a harmonic trap. The impedance network coupled with the resonator provides both the trapping mechanism and the necessary impedance transformation. This multi-functionality eliminates the need for separate dedicated trap circuits, reducing device complexity while maintaining effective harmonic suppression.
3Object-generated harmful factors
If a deep trap is created to suppress harmonics effectively, then harmonic suppression improves, but insertion loss increases
Solution Approach 1:
The patent applies local quality by creating a highly selective trap that is effective only at the specific harmonic frequency while maintaining excellent transmission at the fundamental frequency. The acoustic wave resonator is precisely tuned to resonate at the harmonic frequency (e.g., 2f0), creating a localized high-impedance path only at that frequency. This localized effect ensures deep harmonic suppression without introducing significant insertion loss across the entire frequency band.
Solution Approach 2:
The patent uses partial action by implementing a trap circuit that provides excessive suppression specifically at the harmonic frequency while maintaining minimal impact on the fundamental frequency. The impedance network is designed to provide a deep trap (excessive action) at the harmonic frequency, but this excessive suppression is localized only where needed, preventing overall energy loss. The Q-factor of the resonator is optimized to provide strong trapping at the harmonic while allowing full transmission of the fundamental signal.
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 solution effectively reduces H2 emissions in radio frequency systems, meeting stringent specifications by using an acoustic assisted trap circuit that provides a deep trap with minimal loss penalty, avoiding the need for additional surface mount devices and reducing area consumption, while maintaining steepness in frequency response.
Implementation Method 1
an acoustic wave resonator and an impedance network that are together configured to provide a trap for a harmonic associated with the first acoustic wave filter
Implementation Method 2
a first acoustic wave filter and a plurality of additional acoustic wave filters coupled together with the first acoustic wave filter at an antenna node
Implementation Method 3
The impedance network can include an inductor. The acoustic wave resonator can be a shunt resonator that is in series with the inductor
Data Source
AI summary
Aspects of this disclosure relate to a multiplexer with an acoustic assisted trap circuit. The multiplexer includes a first acoustic wave filter and a second acoustic wave filter. The first acoustic wave filter can include a bulk acoustic wave resonator. The second acoustic wave filter can include a surface acoustic wave resonator and an impedance network. The surface acoustic wave resonator and the impedance network can together provide a trap for a harmonic associated with the first acoustic wave filter.