Tunable Acoustic Filter Passband for Narrow-Band STR RF Modules
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Solution Overview
Problem
Existing RF front-end modules face challenges in supporting simultaneous transmission and reception (STR) in narrow frequency bands like UNII-4 and UNII-5 due to self-interference caused by out-of-band noise, leading to reduced range and throughput, and current solutions are either inefficient or prohibitively expensive.
Innovation Solution
Implementing a tunable acoustic filter assembly with BAW filters that allow for shifting the transition band using reactive elements or RF cancellation techniques to align the transition band with the desired transmission and reception channels, minimizing self-interference while maintaining a 110 MHz transition width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed acoustic filter is used, then the filter structure is simple and cost-effective, but it cannot support simultaneous transmission and reception in narrow frequency bands due to self-interference
Solution Approach 1:
The patent implements a tunable acoustic filter where the transition band can be dynamically shifted between different frequency positions. This is achieved by making the filter characteristics adjustable rather than fixed, allowing the same filter structure to adapt to different operational modes (transmission/reception) and frequency bands, thereby enabling simultaneous transmission and reception without requiring multiple fixed filters
Solution Approach 2:
The patent changes the frequency parameter of the acoustic filter by shifting the transition band position. By adjusting the transition band width and position, the filter can accommodate different frequency allocations for transmission and reception channels, resolving the self-interference issue while maintaining a single filter structure
2Reliability
If the transition band is made wider to reduce self-interference, then signal quality improves, but the available frequency bandwidth for communication decreases
Solution Approach 1:
The patent makes the transition band width dynamic rather than fixed. The transition band can be adjusted to be wider when needed for filtering performance and narrower when bandwidth is required for communication, allowing the system to optimize between signal quality and available bandwidth based on operational requirements
Solution Approach 2:
The patent employs periodic switching between different transition band configurations, alternating between wider transition bands for interference reduction and narrower transition bands for bandwidth efficiency, depending on whether the system is in transmission or reception mode
3Adaptability or versatility
If multiple fixed filters are used to support multiple bands, then all frequency bands can be supported, but the device complexity and cost increase significantly
Solution Approach 1:
The patent designs a single acoustic filter that can perform multiple functions by tuning the transition band to different positions. This universal filter replaces what would otherwise require multiple fixed filters for different frequency bands, reducing device complexity and cost while maintaining multi-band support capability
Solution Approach 2:
By making the filter characteristics dynamic and tunable, a single filter structure can adapt to serve multiple frequency bands and operational modes, eliminating the need for multiple dedicated filters and thereby reducing overall system complexity
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
Enables efficient use of both UNII-4 and UNII-5 channels with reduced interference, improving signal quality and throughput without increasing costs or complexity.
Implementation Method 1
a first filter configured to allow signals received via an antenna node to pass at a first band; a second filter configured to allow the signals received via the antenna node to pass at a second band
Implementation Method 2
each of the first filter and the second filter includes at least one resonator, which is selectively connected with a reactive element by the control signal to adjust a resonance frequency or an anti-resonance frequency of the resonator
Implementation Method 3
a location of the transition band is shifted using a RF cancellation that involves adding a phase-inverted signal according to the control signal
Data Source
AI summary
An acoustic filter assembly for operating at a target band including multiple spaced sub-target bands. The filter assembly includes a first filter that passes a first band and a second filter that passes a second band. The first filter and the second filter have a transition band between the first band and the second band that is wider than the spacing between the sub-target bands. An interface receives a control signal that controls the transition band to be shifted between a first position and a second position, such that an upper part of a lower sub-target band is covered by the first band in the first position, and a lower part of an upper sub-target band is covered by the second band in the second position.