Switchable RF Filter Topology for Pass-Band Tuning and Lower Edge Loss
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Solution Overview
Problem
Existing tunable radio-frequency filters face challenges in changing the frequencies of pass bands and attenuation poles while minimizing loss at the edges of the pass band, as the anti-resonant frequency remains largely unchanged, leading to increased insertion loss.
Innovation Solution
A radio-frequency filter design incorporating a series arm circuit and a parallel arm circuit with multiple resonators and switches, allowing for independent control of resonant and anti-resonant frequencies through switch states, enabling changes in pass band and attenuation pole frequencies while reducing edge loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the resonant frequency is changed to adjust the attenuation pole frequency, then the attenuation pole frequency can be changed, but the anti-resonant frequency remains unchanged causing increased insertion loss at the pass band edge
Solution Approach 1:
The parallel arm circuit is segmented into multiple independent resonators (first parallel arm resonator, second parallel arm resonator, third parallel arm resonator), each with different resonant and anti-resonant frequencies. This segmentation allows selective control of different frequency characteristics through individual switches, enabling independent adjustment of attenuation poles and pass bands without compromising each other.
Solution Approach 2:
The patent introduces switches that can dynamically change the circuit configuration by connecting or disconnecting specific resonators. This dynamic reconfiguration allows the filter to adaptively adjust both resonant and anti-resonant frequencies in response to switching operations, maintaining optimal performance across different operating conditions and frequency adjustments.
2Adaptability or versatility
If multiple resonators with different resonant and anti-resonant frequencies are used, then both pass band and attenuation pole frequencies can be changed, but the device complexity increases
Solution Approach 1:
Each resonator in the parallel arm circuit serves multiple functions: the first parallel arm resonator provides both a pass band and an attenuation pole, the second parallel arm resonator provides another pass band and attenuation pole, and the third parallel arm resonator provides an additional attenuation pole. This multi-functionality allows the circuit to achieve complex frequency selection capabilities while maintaining a relatively compact structure.
Solution Approach 2:
The patent combines multiple resonators in a parallel configuration where they share common connection points and control switches. This merging approach allows the resonators to work together synergistically, achieving sophisticated frequency tuning capabilities through a unified circuit structure rather than separate independent circuits, thereby managing 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
The design effectively changes both pass band and attenuation pole frequencies, reducing loss at the edges of the pass band by varying resonant and anti-resonant frequencies in response to switch states, thereby improving filter performance.
Implementation Method 1
a resonant frequency that is a singular point at which the impedance of the parallel arm circuit is minimum changes in response to switching between an on state (conductive state) and off state (nonconductive state) of the switch. Therefore, the frequency of an attenuation pole that is provided by the resonant frequency can be changed. However, an anti-resonant frequency that provides a pass band and that is a singular point at which the impedance of the parallel arm circuit is maximum remains almost unchanged.
Data Source
AI summary
A filter (10) includes a series arm circuit (11) and a parallel arm circuit (12). The parallel arm circuit (12) includes a parallel arm resonator (p1), a variable frequency circuit (12T), and a parallel arm resonator (p2) connected in parallel with a circuit in which the parallel arm resonator (p1) and the variable frequency circuit (12T) are connected in series. The variable frequency circuit (12T) includes a parallel arm resonator (p3) and a switch (SW) connected in parallel with the parallel arm resonator (p3), and is configured to change frequencies of a pass band and a frequency of an attenuation pole by switching between an on state and off state of the switch (SW). A resonant frequency and anti-resonant frequency of the parallel arm resonator (p1) are respectively different from a resonant frequency and anti-resonant frequency of the parallel arm resonator (p2).