Microwave Filter Dielectric Element Geometry
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Solution Overview
Problem
Conventional microwave filters suffer from high dielectric and metallic losses, leading to a non-optimal quality factor and poor isolation, especially when operating at higher frequencies, making them unsuitable for applications like the Ku band where parasitic modes are not effectively suppressed.
Innovation Solution
A microwave filter design featuring a cylindrical cavity with a dielectric element having a polygonal section and pyramidal portions, where the vertices are short-circuited to the conductive walls, optimizing the electromagnetic field distribution to minimize losses and enhance isolation, allowing for improved performance across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dielectric resonator is used in a microwave filter, then the resonance frequency can be controlled, but dielectric losses increase leading to reduced quality factor
Solution Approach 1:
The dielectric element is designed with non-uniform geometry (pyramidal portions with vertices short-circuited to cavity walls) to create localized regions of different dielectric properties. This allows the electric field to be concentrated in specific areas with lower loss, while other regions provide mechanical support and frequency control, thus resolving the contradiction between resonance control and loss reduction.
2Length of moving object
If the filter operates at higher frequencies (e.g., Ku band), then the filter dimensions can be reduced, but the quality factor degrades due to increased losses
Solution Approach 1:
The cavity is designed with a cylindrical shape and the dielectric element incorporates pyramidal portions with curved transitions. This curvature reduces electromagnetic field concentration at sharp edges and corners, thereby reducing parasitic modes and losses at high frequencies. The rounded geometry maintains resonance control while minimizing energy loss, enabling high quality factor operation in the Ku band.
3Manufacturing precision
If vertices of the dielectric element are short-circuited to cavity walls, then mechanical positioning precision is improved, but electrical contact losses may increase
Solution Approach 1:
The vertices of the dielectric element are pre-shaped (truncated or rounded) during manufacturing to match the cavity wall geometry. This preliminary preparation ensures optimal mechanical contact and electrical connection when the filter is assembled, achieving both precise positioning and minimal contact losses without requiring complex adjustment mechanisms.
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 filter achieves a high quality factor of at least 18000 and a spurious-free range of 500 MHz on either side of the resonance frequency, with a power handling of 300 W per channel, effectively suppressing parasitic modes and maintaining optimal performance in the Ku band.
Implementation Method 1
A microwave filter having at least one resonant mode comprising at least one cavity at least partially closed with the aid of conductive walls
Implementation Method 2
at least one dielectric element disposed in said cavity and comprising: a first portion having a thickness along said longitudinal axis and a section along a plane perpendicular to said longitudinal axis
Implementation Method 3
at least two vertices are short-circuited together by the conductive walls of the cavity, via an electrical or microwave contact between the vertices and the walls
Implementation Method 4
The mechanical contact allows exact and reproducible positioning of the resonant element in the cavity and the heat transfer between the resonator element and the walls is markedly improved
Data Source
Figure 1a~1b
Figure 1c~2
Figure 3a~3b
AI summary
The invention relates to a microwave filter (10) having at least one resonant mode comprising: - at least one cavity (11) at least partially closed by means of conductive walls (12) and, - having a cylindrical outer surface defined by a direction curve (C) described by a generatrix and having a point of symmetry (Sy), an axis passing through a point of symmetry and parallel to said generatrix being called the longitudinal axis (z) of said cavity (11) and, - at least one dielectric element (13) disposed in said cavity and comprising: - a first portion (131) having a thickness (e) along said longitudinal axis (z) and a cross-section along a plane perpendicular to said longitudinal axis (z) whose vertices (s1, s2, s3, s4) are distributed according to a polygon, and of which at least two vertices are short-circuited together by said conductive walls (12) of said cavity,via electrical or microwave contact between said vertices and said walls, -at least one pyramidal portion (132, 133) comprising an apex (Asup) and a base coinciding with an extremal section of said first portion (131).