Balanced Filter Resonator Layout for Compact Multiplexers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing balanced filters face challenges in reducing size while maintaining filter characteristics, particularly in portable communication devices where space and thickness are critical.
Innovation Solution
The proposed filter device incorporates a combination of short-circuited and open-type resonators, where a short-circuited resonator is used on the unbalanced terminal side and an open-type resonator is used on the balanced terminal side, achieving a reduction in size while maintaining favorable balance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If open-type resonators are used in balanced filters, then favorable balance characteristics and high Q factor are achieved, but the line length increases to λ/2 causing larger device size
Solution Approach 1:
The resonator is divided into two distinct types: short-circuited resonators for the unbalanced terminal side and open-type resonators for the balanced terminal side. This segmentation allows each resonator type to be optimized for its specific function, with short-circuited resonators providing compact size (λ/4 length) and open-type resonators providing excellent balance characteristics (λ/2 length) where needed.
Solution Approach 2:
Different resonator structures are applied to different locations within the filter: short-circuited resonators are used where size reduction is critical (unbalanced terminal side), while open-type resonators are used where balance characteristics are critical (balanced terminal side). This local differentiation optimizes overall filter performance by placing the right structure in the right position.
2Length of stationary object
If short-circuited resonators are used, then the line length is reduced to λ/4 achieving compact size, but balance characteristics and Q factor deteriorate compared to open-type resonators
Solution Approach 1:
The filter is segmented into two functional zones with different resonator types. Short-circuited resonators are deployed in zones where size is the primary concern, while open-type resonators are deployed in zones where balance characteristics are paramount. This spatial segmentation resolves the contradiction by allowing each resonator type to excel in its designated area.
Solution Approach 2:
The filter employs an asymmetric configuration where not all resonators are of the same type. Instead, the design deliberately uses different resonator structures (short-circuited and open-type) in different positions, creating an asymmetric layout that optimizes both size and performance characteristics simultaneously.
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
This configuration allows for a reduction in the size of the balanced filter while preventing degradation in filter characteristics, making it suitable for use in portable communication devices.
Implementation Method 1
a resonator connected to an unbalanced terminal and a resonator connected to a balanced terminal are electromagnetically coupled to transmit signals
Data Source
AI summary
A filter device includes an unbalanced terminal, balanced terminals, and first and second resonant circuits. The first resonant circuit is connected to the unbalanced terminal. The second resonant circuit is connected to the balanced terminals and electromagnetically coupled with the first resonant circuit. The first resonant circuit includes a resonator in which an inductor and a capacitor are connected in parallel between the unbalanced terminal and a reference potential. The second resonant circuit includes a resonator including an inductor connected between the balanced terminals and capacitors connected in series between the balanced terminals.