Tunable RF Filter with Variable Non-Resonant Elements
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Solution Overview
Problem
Current microwave band-pass filters face challenges in achieving low insertion loss while maintaining high selectivity and tunability, especially in wide frequency ranges, leading to increased size and cost due to the need for multiple resonators and inefficient tuning methods.
Innovation Solution
The design incorporates a signal transmission path with resonant and non-resonant elements, where non-resonant elements with adjustable susceptance values create transmission and reflection zeros to form pass bands within sub-bands, allowing for tunability without significantly adjusting resonant elements, thus minimizing insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional filter designs use multiple resonators to achieve high selectivity and wide frequency range, then selectivity and frequency range are improved, but insertion loss increases and device size increases
Solution Approach 1:
The patent changes the fundamental design parameter from using multiple resonators to using a single resonator with non-resonant elements. This parameter change allows achieving high selectivity through the interaction between the resonant element and non-resonant coupling elements, rather than through multiple resonators, thereby reducing insertion loss while maintaining selectivity.
Solution Approach 2:
The patent extracts the resonant function to a single resonant element and separates the frequency selection function to non-resonant coupling elements. This extraction allows the resonant element to operate at a fixed frequency with high Q-factor, while the non-resonant elements provide the frequency selectivity, reducing overall insertion loss.
2Adaptability or versatility
If conventional filter designs use multiple resonators to cover wide frequency ranges, then frequency range is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the single resonant element universal by enabling it to operate at a fixed frequency while the non-resonant coupling elements provide the frequency tuning capability. This multi-functionality allows one resonator to replace multiple resonators, covering wide frequency ranges through the non-resonant elements without increasing device complexity.
Solution Approach 2:
The patent introduces dynamic tuning capability through non-resonant coupling elements that can be adjusted to change the operating frequency. This dynamic adjustment allows the filter to cover wide frequency ranges without requiring multiple fixed-frequency resonators, thereby reducing device complexity.
3Adaptability or versatility
If conventional filter designs adjust resonant frequencies to achieve tuning, then tunability is improved, but insertion loss increases due to resistance introduction
Solution Approach 1:
The patent extracts the tuning function from the resonant element and places it in the non-resonant coupling elements. This separation allows frequency tuning to be achieved by adjusting the non-resonant elements, which do not introduce significant resistance, thereby maintaining low insertion loss while achieving tunability.
Solution Approach 2:
The patent inverts the conventional approach by making the resonant element fixed-frequency and using non-resonant elements for tuning. This inversion allows tuning to be achieved without modifying the resonant element, avoiding the introduction of resistance and maintaining low insertion loss.
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 enables quick tuning with reduced insertion loss, allowing the filter to operate across a wide frequency range with fewer resonators, improving selectivity and sensitivity while reducing size and cost.
Implementation Method 1
a plurality of resonant elements disposed along the signal transmission path between the input and the output... The resonant elements are coupled together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements
Implementation Method 2
The non-resonant elements have susceptance values that locate at least one reflection zero within the stop band to create a pass band in one of the at least one sub-bands
Data Source
AI summary
A tunable radio frequency (RF) filter is provided. The RF filter comprises a signal transmission path having an input and an output, a plurality of resonant elements disposed along the signal transmission path between the input and the output, and a plurality of non-resonant elements coupling the resonant elements together. The resonant elements are coupled together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements, and at least one sub-band between the transmission zeroes. The non-resonant elements comprise at least one variable non-resonant element for selectively introducing at least one reflection zero within the stop band to create a pass band in one of the sub-bands(s). The variable non-resonant element(s) may be configured for displacing the reflection zero(es) along the stop band to selectively move the pass band within the one sub-band or within selected ones of the sub-bands.