Waveguide Band-Pass Filter Layout for Broadband Spurious Rejection
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Solution Overview
Problem
Existing waveguide band-pass filters are unable to provide continuous broadband rejection of unwanted frequencies for all waveguide modes, often requiring cascaded filters, which increases size, weight, and cost, while also having high in-band insertion loss and low power handling.
Innovation Solution
A waveguide band-pass filter design using a sequence of rectangular resonators with the same fundamental resonance frequency but different spurious frequency responses, where spurious frequencies are scattered across the stopband, allowing for high power handling, reduced size, and mass, and improved manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If evanescent-mode operation is used to provide compact and light filters, then size and mass are reduced, but in-band insertion loss increases and power handling decreases
Solution Approach 1:
The patent transitions from evanescent-mode operation to resonant-mode operation by changing the operational parameters of the waveguide filter. This involves designing resonators that operate at their fundamental resonant frequency rather than relying on evanescent wave decay, thereby reducing insertion loss while maintaining compact dimensions through optimized resonator geometry and coupling mechanisms.
2Reliability
If cascaded filters are used to provide broadband rejection, then frequency rejection performance is improved, but size, weight, and cost increase
Solution Approach 1:
The patent merges multiple filter functions into a single integrated waveguide filter structure. By designing resonators with specific quality factors and coupling them through optimized irises, the filter achieves broadband frequency rejection (stopband) and passband characteristics simultaneously within one compact assembly, eliminating the need for cascaded filter configurations.
Solution Approach 2:
The waveguide filter is designed to perform multiple functions simultaneously: it provides bandpass filtering, broadband stopband rejection, and maintains low insertion loss all within a single device. The resonator design and coupling scheme enable the filter to handle multiple frequency ranges effectively without requiring separate filter stages.
3Measurement precision
If resonators with the same fundamental resonance frequency are used, then frequency selection is improved, but spurious frequency responses create interference
Solution Approach 1:
The patent applies local quality by introducing variations in resonator geometry and coupling characteristics at specific locations within the filter. Each resonator is designed with slight dimensional differences or different coupling iris configurations, which causes spurious frequency responses to be scattered across different frequency points in the stopband rather than appearing as concentrated interference near the passband.
Solution Approach 2:
The patent introduces asymmetry in the resonator designs by varying the dimensions and coupling configurations of individual resonators. This asymmetric design ensures that while all resonators share the same fundamental resonant frequency for the passband, their spurious mode frequencies are distributed differently, scattering harmful spurious responses across the stopband spectrum.
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 design achieves broadband rejection of unwanted frequencies, high power handling, and reduced size and mass, while maintaining low insertion loss and cost, making it suitable for wide-band applications such as satellite communication.
Implementation Method 1
a plurality of rectangular waveguide cavities defining waveguide resonators, each resonant cavity configured to define the same fundamental resonant frequency
Implementation Method 2
each resonant cavity includes a capacitive iris positioned coupling the cavity sections to one another
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
A bandpass filter has a plurality of resonant cavities. The plurality of resonant cavities are arranged into a sequence of adjacent resonant cavities. Each resonant cavity is configured to define the same fundamental resonant frequency. The filter includes a plurality of coupling irises, with one of the coupling irises positioned between each pair of adjacent resonant cavities. Each resonant cavity includes a plurality of cavity sections. Each resonant cavity includes a capacitive iris positioned coupling the cavity sections to one another. The frequency of secondary resonance modes varies amongst the resonant cavities in the plurality of resonant cavities.