Elongated Resonator Coaxial Filter Cross-Coupling
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Solution Overview
Problem
Existing microwave filters require cross-coupling probes to achieve transmission zeros, which introduce unwanted resonances, complicate tuning, and increase size and cost, while also facing structural constraints with input and output connectors on opposite sides.
Innovation Solution
A microwave filter design utilizing elongated resonators within a coaxial housing, where the elongated resonators are cross-coupled without the need for cross-coupling probes, allowing for transmission zeros in both lower and upper stopbands, and enabling band-pass filtering without additional structural components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cross-coupling probes are used to achieve transmission zeros, then the filter can suppress unwanted frequencies, but the filter size increases and tuning becomes more complex
Solution Approach 1:
The patent removes the cross-coupling probe structure entirely from the filter design. Instead of using probes to achieve cross-coupling between resonators, the invention uses the inherent coupling through the common ground plane and cavity structure, thereby eliminating the need for additional tuning components and reducing overall device complexity while maintaining the ability to create transmission zeros for frequency suppression
Solution Approach 2:
The ground plane and cavity structure serve multiple functions simultaneously: they provide mechanical support, establish electromagnetic coupling between resonators, and enable transmission zero formation. This multi-functionality eliminates the need for separate cross-coupling probes, reducing the number of components and simplifying the overall filter structure
2Reliability
If cross-coupling probes are used to achieve transmission zeros, then the filter can suppress unwanted frequencies, but the filter size increases
Solution Approach 1:
By removing the cross-coupling probe structure, the patent eliminates the additional space required for probe installation, adjustment mechanisms, and associated mounting hardware. The filter achieves the same frequency suppression function using the existing resonator and cavity structure, thereby reducing the overall filter volume
3Strength
If traditional filter structures are used with connectors on opposite sides, then structural integrity is maintained, but cross-coupling requires additional components
Solution Approach 1:
The patent makes the cavity structure perform multiple functions: it maintains structural integrity as the housing while simultaneously providing the coupling mechanism between resonators. The ground plane serves both as a structural element and as the coupling path, eliminating the need for separate cross-coupling probes and reducing component quantity
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 design enhances filter performance by eliminating probe-related issues, simplifying tuning, reducing size, and maintaining structural integrity with connectors on opposite sides, while achieving desired frequency responses without increasing complexity or cost.
Implementation Method 1
A microwave filter is an electromagnetic device that can be tuned to pass energy within bands of frequencies (i.e. the passband) encompassing resonant frequencies of the filter, while substantially suppressing unwanted frequencies (i.e. the stopband)
Implementation Method 2
The first resonator and the third resonator are cross-coupled
Data Source
AI summary
A microwave filter has a housing defining an inner cavity. A first resonator is positioned in a first portion of the inner cavity. A second resonator is positioned in a second portion of the inner cavity. A third resonator is positioned in a third portion of the inner cavity. The first resonator and the third resonator are cross-coupled via an iris. The second resonator is elongated and is coupled to the first resonator and the third resonator. The resulting microwave filter has a frequency response having a transmission zero in the lower stopband. A high-pass filter is realized without the use of a cross-coupling probe.