Bandstop Filters Using Mixed Electric Magnetic Coupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional microwave bandstop filters have long through-line lengths, leading to increased passband insertion loss, size, and weight, and are difficult to tune, which affects their frequency response.
Innovation Solution
The use of mixed electric and magnetic field coupling between resonators to minimize physical length, allowing for phase offsets that absorb the length of quarter-wavelength inverters, resulting in reduced through-line length and improved filter design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional microwave bandstop filter topology with quarter-wavelength admittance inverters is used, then symmetric notch frequency response is achieved, but total through-line length becomes long for high-order filters
Solution Approach 1:
The patent transitions from conventional in-line coupling to three-dimensional evanescent mode coupling between resonators. By utilizing evanescent fields in the vertical dimension (through coupling apertures in a common ground plane), the filter achieves the required phase relationships without long through-lines, resolving the contradiction between frequency response symmetry and through-line length.
2Reliability
If long through-line is used in conventional bandstop filters, then quarter-wavelength inverter requirements are met, but passband insertion loss increases
Solution Approach 1:
The patent extracts the quarter-wavelength inverter function from the through-line structure and implements it through evanescent mode coupling between resonators. This separation allows the through-line to be minimized while the coupling structures provide the necessary phase shift, thereby reducing insertion loss while maintaining frequency response accuracy.
3Reliability
If conventional bandstop filter topology is used, then filter specifications are met, but circuit size and weight increase
Solution Approach 1:
The patent merges the functions of the through-line and quarter-wavelength inverters into a compact evanescent mode coupling structure. By combining these functions into the resonator coupling mechanism itself, the overall circuit size is reduced while maintaining all required filter specifications.
4Device complexity
If traditional through-line structure is used, then filter design is simplified, but tuning difficulty increases in production environments
Solution Approach 1:
The patent introduces adjustable coupling aperture dimensions that can be tuned during production to optimize filter performance. This dynamic adjustment capability allows for easy tuning of the evanescent mode coupling strength, compensating for manufacturing variations and enabling precise frequency response control without complicating the overall design.
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 approach reduces the total through-line length of bandstop filters to a single coupling section length, independent of filter order, leading to smaller, lighter, and lower insertion loss filters with improved frequency selectivity.
Implementation Method 1
uses mixed electric and magnetic field coupling to reduce physical length between coupled lines
Implementation Method 2
with a ratio of electric to magnetic coupling of each resonator set such that phase offsets produced by the resonators absorb some or all of the length of quarter-wavelength inverters between adjacent resonators
Data Source
AI summary
Systems and methods are provided for creating higher order microwave bandstop filters with total through-line length of significantly less than one-quarter wavelength at the filter center frequency. The mixed electric and magnetic field coupling bandstop filter topologies provided by embodiments of the present disclosure can be used to reduce the size, weight, and throughline insertion loss of microwave bandstop filters. In an embodiment, if the relative field strengths are intelligently designed for each coupling structure, effective phase offsets can be produced between resonators along the through line. These phase offsets can be used to absorb some or all of the length of the λ/4 inverters between resonators.