RF Filter Circuit With Switchable Passband for Dual-Band Duplexing
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Solution Overview
Problem
Conventional radio frequency front end circuits require complex configurations and large sizes due to the need for multiple duplexers and switches to switch between two frequency bands, leading to increased circuit complexity and size.
Innovation Solution
A radio frequency filter circuit utilizing a series-arm resonator and parallel-arm resonators with a switch element that allows for adjustable passband by switching between different resonant frequencies, enabling exclusive selection between two frequency bands using a simplified and compact SPST-type configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple duplexers and SPDT switches are used to switch between two frequency bands, then frequency band switching capability is achieved, but circuit complexity and device size increase
Solution Approach 1:
The patent merges the functions of multiple duplexers and SPDT switches into a single BPF with adjustable passband. By using a single resonator circuit whose resonant frequency can be tuned, the patent combines frequency selection and band switching functions that previously required separate components, thereby reducing circuit complexity while maintaining frequency band switching capability
Solution Approach 2:
The BPF with adjustable passband serves multiple functions simultaneously: it acts as a frequency selector, a band switch, and a filter. By making the passband adjustable through resonator frequency tuning, a single device performs the work of multiple specialized components (duplexers and switches), achieving multi-functionality that reduces overall system complexity
2Adaptability or versatility
If multiple duplexers and SPDT switches are used to switch between two frequency bands, then frequency band switching capability is achieved, but device size increases
Solution Approach 1:
The patent merges the physical presence of multiple duplexers and switches into a single compact BPF structure. By integrating frequency selection and band switching functions into one resonator-based filter, the device occupies less space while maintaining the ability to switch between frequency bands, directly addressing the size reduction requirement
3Device complexity
If a simplified filter circuit configuration is used, then device complexity and size are reduced, but frequency band switching capability may be compromised
Solution Approach 1:
The patent introduces dynamic adjustability to the BPF passband through resonator frequency tuning. This dynamic capability allows the simplified filter circuit to adapt and switch between different frequency bands, ensuring that frequency band switching capability is maintained despite the reduction in circuit complexity. The dynamic resonant frequency adjustment compensates for the simplified structure
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 solution simplifies and miniaturizes the filter circuit, allowing for efficient switching between two frequency bands while maintaining low loss characteristics and adjustable bandwidth, suitable for multimode/multiband communication systems.
Implementation Method 1
acoustic wave filters that use acoustic waves have been widely used as band pass filters
Implementation Method 2
acoustic wave filters that use acoustic waves have been widely used
Data Source
AI summary
A radio frequency filter circuit (22A) includes a series-arm resonator (22s), a parallel-arm resonator (22p1), a parallel-arm resonator (22p2) that is connected between a node x1 and a ground terminal, a switch (22SW) that is arranged between the node x1 and the ground terminal and switches between electrical connection and electrical non-connection of a path connecting the node x1, the parallel-arm resonator (22p2), and the ground terminal. The parallel-arm resonator (22p1) and a series circuit in which the parallel-arm resonator (22p2) and the switch (22SW) are connected in series are connected in parallel between the node x1 and the ground terminal. A resonant frequency (frp) of the parallel-arm resonator (22p1) is lower than a resonant frequency (frs) of the series-arm resonator (22s). A resonant frequency (frp2) of the parallel-arm resonator (22p2) is higher than the resonant frequency (frp) of the parallel-arm resonator (22p1).