Filtering Circuit Cross-Coupling Sideband Interference Suppression
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Solution Overview
Problem
Conventional high-frequency filters in communication systems face challenges in effectively suppressing sideband interferences and maintaining low power loss, particularly due to limitations in reducing gap width between coupled lines, which affects signal coupling and increases fabrication complexity and cost.
Innovation Solution
A filtering circuit structure with a resonant circuit and cross-coupling portions that transmit signals through cross-coupling, allowing for the production of transmission zeros around the operation band to suppress sideband interferences, while maintaining a simple structure and low fabrication costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gap width between coupled lines is reduced to increase signal coupling, then the coupling efficiency is improved, but the fabrication precision requirement increases and process variation sensitivity increases
Solution Approach 1:
The patent introduces cross-coupling between non-adjacent resonators (e.g., 1st and 3rd resonators) that are separated by at least one intermediate resonator. This spatial dimensionality change allows signal coupling without requiring small gap widths between adjacent lines, thereby maintaining coupling efficiency while avoiding fabrication precision issues.
Solution Approach 2:
The patent uses intermediate resonators as mediators in the cross-coupling structure. The cross-coupling portions connect non-adjacent resonators through the intermediate resonator system, enabling signal transmission while maintaining larger, more manufacturable gap widths between coupled lines.
2Reliability
If the line widths of coupled lines are reduced to increase coupling, then the coupling efficiency is improved, but the quality factor of resonators decreases and transmission loss increases
Solution Approach 1:
Instead of reducing line widths to improve coupling, the patent employs cross-coupling between non-adjacent resonators. This approach maintains standard line widths and resonator quality factors while achieving the desired coupling effect through the alternative coupling path.
3Reliability
If the substrate thickness is increased to improve coupling, then the coupling efficiency is improved, but the device complexity and cost increase
Solution Approach 1:
The patent achieves improved coupling through cross-coupling architecture rather than increasing substrate thickness. This maintains a standard, simple substrate structure while obtaining the desired coupling performance through the innovative connection topology between non-adjacent resonators.
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 proposed filtering circuit achieves improved sideband interference suppression and reduced power loss, enhancing communication quality and yield in mass production with a cost-effective and easy-to-implement design.
Implementation Method 1
the coupled lines 130_1 ̃130_N are all microstrips of quarter wavelength, wherein one terminals of the coupled lines 130_1 ̃130_N are grounded, and the other terminals thereof are open. Since the coupled lines 130_1 ̃130_N are equivalent to resonators composed of capacitors and inductors
Implementation Method 2
a first coupling portion coupled to the ith resonator, and a second coupling portion coupled to the jth resonator... a part of the input signal received by the input terminal is transmitted from the 1st resonator to the ith resonator and then transmitted to the second coupling portion via the first coupling portion through cross-coupling
Data Source
AI summary
A filtering circuit and a structure thereof are provided. The filtering circuit includes an input terminal, an output terminal, a resonant circuit, a first coupling portion, and a second coupling portion. The resonant circuit is coupled between the input terminal and the output terminal and includes M resonators which are arranged in sequence. A signal received by the input terminal can be transmitted to the output terminal by the resonant circuit through inter-coupling between adjacent resonators. The first coupling portion and the second coupling portion are respectively coupled to non-adjacent resonators. A part of the signal received by the input terminal is transmitted to the second coupling portion via the first coupling portion through cross-couple. Thereby, sideband interference can be further suppressed.