Rotating Dielectric Microwave Filter Tuning
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Solution Overview
Problem
Existing frequency-tunable bandpass filters in the microwave domain face challenges such as complex designs, high electrical energy consumption, unreliability, limited power handling, and significant degradation of quality factor Q and RF losses due to frequency tunability, especially in satellite applications.
Innovation Solution
A tunable bandpass filter design featuring a resonator with a cylindrical conductive wall and a dielectric element that rotates between two positions, altering its orientation to change the central resonant frequency, maintaining high quality factor and power handling capabilities while minimizing RF losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If passive semiconductor components or MEMS are used for frequency tuning, then frequency tunability is achieved, but device complexity, energy consumption, and unreliability increase
Solution Approach 1:
The patent applies the dynamics principle by making the dielectric element rotatable within the resonator cavity. The dielectric element can be positioned at different angular orientations (e.g., 0° for first frequency, 90° for second frequency) to dynamically change the resonant frequency without requiring complex semiconductor components or MEMS structures. This mechanical rotation provides simple yet effective frequency tuning.
Solution Approach 2:
The patent changes the physical orientation parameter of the dielectric element to achieve frequency tuning. By rotating the dielectric element to different positions within the cavity, the electromagnetic field distribution and resonant characteristics are modified, enabling frequency adjustment from first frequency to second frequency without changing the fundamental structure or material properties.
2Adaptability or versatility
If frequency tuning is implemented using conventional methods, then central frequency adjustment is achieved, but quality factor Q and RF losses are significantly degraded
Solution Approach 1:
The patent applies local quality by strategically positioning the dielectric element at specific locations within the resonator cavity where it interacts with the electromagnetic field in a controlled manner. The dielectric element is placed at positions that minimally disrupt the overall field distribution, thereby maintaining high quality factor while enabling frequency tuning through orientation changes rather than position changes.
Solution Approach 2:
The dynamic rotation of the dielectric element allows frequency tuning without introducing lossy components. The dielectric material itself remains stationary in terms of its material properties, and only its orientation changes, avoiding the introduction of switches, varactors, or other components that would degrade Q factor and increase RF losses.
3Measurement precision
If metal screws are used to adjust resonance frequencies, then precise central frequency value is obtained, but manufacturing time and cost increase significantly
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-positioning the dielectric element at specific angular orientations that correspond to desired resonant frequencies. During manufacturing, the dielectric element is simply installed at the predetermined orientation (e.g., aligned with specific cavity axes), eliminating the need for time-consuming empirical adjustments with metal screws while ensuring precise frequency values are achieved.
Solution Approach 2:
The patent utilizes the asymmetric interaction between the dielectric element and the electromagnetic field modes of the resonator. By orienting the dielectric element at specific asymmetric positions (e.g., 0° vs 90° orientations), distinct resonant frequencies are achieved. This asymmetric positioning provides precise frequency control through simple geometric arrangement rather than complex mechanical adjustments.
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 precise frequency tunability with reduced sensitivity to temperature and mechanical adjustments, maintaining high quality factor and power handling, and is more compact and efficient compared to traditional solutions.
Implementation Method 1
each resonator comprising: a cavity having a substantially cylindrical conductive wall along an axis Z... at least one dielectric element arranged inside the cavity, said resonator resonating according to a mode
Data Source
Figure 1
Figure 2a~3b
Figure 4a~4b
AI summary
A frequency tunable microwave bandpass filter comprises a resonator, including: a cavity with conducting wall substantially cylindrical with axis Z having height H, and partially closed at both ends; and a dielectric element inside the cavity. The resonator resonates at two perpendicular polarizations having distributions of electromagnetic field in the cavity deduced from eachother by 90° rotation. The element rotates about an axis substantially perpendicular to axis Z, between a first and second position. The element comprises a first end wherein: in a first position the element is disposed substantially in a plane perpendicular to axis Z and the center of the first end is disposed at a height in the cavity corresponding substantially to an electric field minimum; and in a second position the element is substantially parallel to Z and the first end is disposed in a plane corresponding to an electric field maximum within +/−30%.