Switchable RF Filter Multiplexer for Wideband and Multiband Paths
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Solution Overview
Problem
Existing frequency-tunable filter devices require a large circuit scale to switch between a filter with a wide passband and a multiplexer that demultiplexes or multiplexes multiple narrow passbands, which is inefficient and increases complexity.
Innovation Solution
A filter device configuration using two filters with non-overlapping frequency bands and two switch elements that can be switched between conducting and non-conducting states to form either a wide passband filter or a multiplexer, optimizing circuit size and performance by controlling off-capacitance and phase shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a frequency-tunable filter and other filters are connected to a common terminal to switch between wide passband and narrow passband modes, then the system can achieve multi-band functionality, but the circuit scale increases due to requiring three filters
Solution Approach 1:
The patent combines two narrow passband filters into a multiplexer structure that shares a common terminal. The multiplexer uses switch elements to selectively connect different filter paths, allowing the system to achieve both wide passband filtering and multi-band narrow passband filtering without requiring three separate filters. This merging reduces the overall filter count while maintaining multi-band adaptability.
Solution Approach 2:
The multiplexer structure serves multiple functions: it acts as a signal router to direct signals to different narrow passband filters, and simultaneously provides the narrow passband filtering function itself. This multi-functionality allows the system to achieve both wide passband and narrow passband modes using fewer components, reducing circuit scale while maintaining versatility.
2Device complexity
If switch elements are used to switch between conducting and non-conducting states to form wide passband filter or multiplexer, then the circuit size is optimized, but insertion loss and attenuation characteristics must be carefully controlled
Solution Approach 1:
The patent optimizes the off-capacitance parameter of the switch elements to minimize their impact on filter performance when in the non-conducting state. By carefully controlling the off-capacitance value, the system reduces insertion loss and maintains proper attenuation characteristics while still achieving compact circuit size through the use of switchable configurations.
Solution Approach 2:
The patent includes mechanisms to control and monitor the switch element states and their impact on signal characteristics. Through feedback control of the switch elements, the system maintains optimal insertion loss and attenuation characteristics while dynamically switching between wide passband filter and multiplexer modes, ensuring reliable performance despite the reduced circuit size.
Data Source
AI summary
A filter device includes: a common terminal; a first input/output terminal; a second input/output terminal; a first filter connected to a first path that connects the common terminal and the first input/output terminal, and having a passband that is a first band; a second filter connected to a second path that connects the common terminal and the second input/output terminal, and having a passband that is a second band having a frequency range that is different from and does not overlap a frequency range of the first band; a first switch element connected between a first node on the first path between the first filter and the first input/output terminal and a second node on the second path between the second filter and the second input/output terminal; and a second switch element on the second path, which is connected between the second node and the second input/output terminal.