RF Filter Passband Switching With Synchronized Impedance Matching
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Solution Overview
Problem
Tunable filters face challenges in switching frequencies of pass bands or attenuation poles without increasing insertion loss within the pass band, as existing technologies often result in higher insertion loss when changing impedance characteristics.
Innovation Solution
A radio-frequency filter device with a switch element that synchronizes with an impedance matching circuit to maintain impedance matching, using a control line for both circuits to adjust switch states and element values, allowing frequency switching while minimizing insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the frequencies of pass band or attenuation pole are changed in a tunable filter, then frequency switching capability is improved, but insertion loss within the pass band increases
Solution Approach 1:
The patent applies dynamics by making the impedance matching circuit adjustable rather than fixed. The impedance matching circuit includes variable elements (such as variable capacitors or inductors) that can be tuned to match the impedance of the filter circuit across different frequency bands. This dynamic adjustment allows the system to maintain low insertion loss while switching between different pass bands or attenuation pole frequencies, resolving the contradiction between frequency adaptability and energy loss.
2Ease of operation
If impedance matching is not maintained during frequency switching, then frequency switching is simplified, but insertion loss increases due to impedance mismatch
Solution Approach 1:
The patent employs feedback mechanisms where the impedance matching circuit is designed to automatically or controllably adjust its parameters based on the operating frequency. Control signals are provided to the impedance matching circuit to adjust its impedance characteristics in response to the selected frequency band. This feedback-based approach ensures impedance matching is maintained during frequency switching, preventing insertion loss while keeping the switching process manageable through automated control.
3Measurement precision
If separate control circuits are used for filter and impedance matching, then control precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the control functions by providing a unified control mechanism that simultaneously manages both the filter circuit and the impedance matching circuit. A single control signal or control unit adjusts both circuits in coordination, ensuring they work together harmoniously during frequency switching. This merging approach maintains control precision by coordinating both circuits while reducing overall device complexity by eliminating the need for completely separate control systems.
Data Source
AI summary
A filter module (20) includes a filter circuit (22) that includes switches (221SW and 224SW), a pass band of the filter circuit (22) being switched in accordance with switching between ON and OFF of the switches (221SW and 224SW); and an impedance matching circuit (21) that is disposed in at least one of a preceding stage and a subsequent stage of the filter circuit (22) and that includes a switch (212SW), an element value for achieving impedance matching being switched in the impedance matching circuit (21) in accordance with switching between ON and OFF of the switch (212SW). The switches (221SW and 224SW) and the switch (212SW) synchronize with each other regarding timing of switching between ON and OFF.