Actively Tuned Filter With Variable Capacitance And Coupling Network
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Solution Overview
Problem
Traditional tunable filters face challenges in maintaining constant bandwidth across a wide frequency range due to sensitive and difficult-to-manage coupling between resonators, requiring complex internal coupling networks and active gain elements to compensate for insertion loss.
Innovation Solution
An actively tuned filter design featuring electromagnetically coupled resonators with variable capacitance connected to the shorted end, allowing the resonant frequency to be tuned without adjusting the coupling between resonators, thus maintaining constant bandwidth across a range of frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional varactor or switched capacitor tuned filter approaches are used to achieve tunability, then the filter can cover a larger frequency band, but insertion loss increases and bandwidth varies across the tuning range
Solution Approach 1:
The patent extracts the coupling network from the tuning mechanism. Instead of using traditional varactor or switched capacitor approaches that directly tune the resonators, this invention uses a separate coupling network with switchable capacitors that controls the coupling between resonators. This extraction allows independent control of coupling strength without directly affecting the resonator tuning, thereby reducing insertion loss and maintaining stable bandwidth across the tuning range.
Solution Approach 2:
The patent introduces a coupling network as an intermediary between the resonators. This coupling network, containing switchable capacitors, acts as a mediator that controls the interaction between resonators. By adjusting the coupling strength through this intermediary rather than directly tuning the resonators, the system achieves frequency tuning while maintaining constant bandwidth and reducing insertion loss.
2Stability of the object's composition
If stepped impedance resonant filters use external and internal lumped element networks to vary coupling across the tuning range, then bandwidth variation is eliminated, but active gain elements are required to compensate for loss variation
Solution Approach 1:
The patent implements self-service by designing a coupling network that automatically maintains constant bandwidth across the tuning range without requiring external active gain elements. The switchable capacitors in the coupling network self-adjust the coupling strength to compensate for tuning-induced bandwidth variations, eliminating the need for additional active components and simplifying the overall filter design.
3Stability of the object's composition
If comb-line and inter-digital filters use switchable coupling capacitors to eliminate bandwidth variation, then constant bandwidth is achieved, but the filter structure becomes complicated
Solution Approach 1:
The patent applies segmentation by separating the filter into distinct functional modules: resonators and a coupling network. The coupling network is further segmented into individual switchable capacitor elements that can be independently controlled. This modular segmentation simplifies the overall structure compared to integrated comb-line or inter-digital designs, while maintaining constant bandwidth through independent coupling control.
4Stability of the object's composition
If the coupling between resonators is tuned as the resonant frequency is tuned to achieve constant bandwidth, then bandwidth stability is improved, but manufacturing and yield costs increase due to sensitivity
Solution Approach 1:
The patent implements dynamics by making the coupling network dynamically adjustable through switchable capacitors. The coupling strength can be changed in discrete steps by switching between different capacitor values, allowing the system to adapt to different operating conditions while maintaining constant bandwidth. This dynamic coupling control is less sensitive to manufacturing tolerances than continuous tuning approaches, reducing manufacturing complexity and improving yield.
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 enables continuous tuning with constant bandwidth, reducing the need for complex internal coupling networks and minimizing sensitivity to capacitance values, resulting in a more efficient and cost-effective tunable filter solution.
Implementation Method 1
The filter includes electromagnetically coupled first and second resonators
Implementation Method 2
a variable capacitance allowing selection of a capacitance to be applied to the first and second resonators
Data Source
AI summary
An actively tuned filter providing a constant bandwidth at a plurality of frequencies. The filter includes first and second electromagnetically coupled coiled resonators, each resonator having an open end configured to receive an input and a shorted end configured to connect the resonator to a ground. The filter further includes a variable capacitance allowing selection of a capacitance to be applied to the first and second resonators, each variable capacitance being connected to the shorted end of the first and second resonators between the resonator and the ground where the axes of the coils of the first and second resonators are aligned along a single axis.