RF Filter Using Hybrid Coupler and Open-Circuit Resonators
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Solution Overview
Problem
Existing RF filters face challenges such as high path loss, limited ability to reject wide frequency bands, and difficulties in improving band edge characteristics, particularly in Band Rejection Filters (BRFs) designed with 50-ohm lines, which require complex structures and lengthened lines for notch characteristics.
Innovation Solution
The integration of a hybrid coupler with a filter unit, allowing for signal division, phase adjustment, and combination, enables the creation of a 'chameleon filter' that can invert signal characteristics, reduce path loss, and facilitate wide frequency band rejection, while also simplifying the design of notch characteristics by dynamically adjusting phase variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a BRF is designed by connecting resonators using a 50-ohm line, then the filter structure is simple, but path loss increases as the number of resonators increases
Solution Approach 1:
The patent inverts the conventional BRF design approach by using open-circuit resonators instead of short-circuit resonators, and connecting them through a hybrid coupler instead of 50-ohm lines. This inversion allows the resonators to be coupled through evanescent fields rather than long transmission lines, significantly reducing path loss while maintaining structural simplicity.
Solution Approach 2:
The hybrid coupler serves as an intermediary element that couples the resonators together, replacing the need for long 50-ohm transmission lines. This intermediary structure enables efficient energy transfer between resonators with minimal loss, solving the path loss problem while keeping the overall structure compact and simple.
2Adaptability or versatility
If the number of resonators is increased to reject a wider frequency band, then frequency band rejection improves, but path loss increases
Solution Approach 1:
By inverting the resonator configuration to use open circuits and coupling them through a hybrid coupler, the patent enables wider frequency band rejection with fewer resonators. The evanescent field coupling mechanism provides broader bandwidth performance compared to traditional 50-ohm line connections, achieving the dual goal of wide rejection and low loss.
Solution Approach 2:
The patent introduces phase shifters that can dynamically adjust the phase of signals coupled between resonators. This dynamic control allows the filter to adaptively optimize its frequency rejection characteristics and maintain low path loss across varying operating conditions and bandwidth requirements.
3Manufacturing precision
If a BRF selectively rejects low or high frequency bands, then specific frequency rejection is achieved, but band edge characteristics deteriorate
Solution Approach 1:
The inverted resonator design with open circuits and hybrid coupler coupling fundamentally changes the frequency response characteristics. This inversion produces superior band edge characteristics with steeper roll-off and better selectivity compared to conventional designs, simultaneously achieving precise frequency rejection and improved band edge performance.
Solution Approach 2:
The patent employs periodic structures in the resonator design and coupling mechanism that create well-defined frequency selectivity. The periodic nature of the evanescent field coupling and phase shifter arrangement produces consistent and reliable band edge characteristics across different frequency bands.
4Adaptability or versatility
If filter replacement is performed to change characteristics, then frequency pass or rejection characteristics can be changed, but communication disconnection occurs and cost increases
Solution Approach 1:
The patent implements a dynamically reconfigurable filter using phase shifters and switching mechanisms that allow real-time adjustment of filter characteristics without physical replacement. The phase shifters can electronically tune the resonator coupling and phase relationships, enabling the filter to adapt its frequency pass or rejection characteristics on-demand, eliminating communication disconnection and replacement costs.
Solution Approach 2:
The hybrid coupler-based resonator structure serves multiple functions simultaneously: it couples resonators, provides phase control, enables frequency selection, and allows dynamic reconfiguration. This multi-functionality replaces what would traditionally require multiple different filter designs, enabling a single filter structure to perform various filtering functions without physical replacement.
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 configuration reduces path loss, enhances band edge characteristics, and allows for easy inversion of signal characteristics, effectively rejecting wide frequency bands and improving notch characteristics, making it suitable for various RF filter applications.
Implementation Method 1
a coupler for receiving an input signal through a first port, dividing the input signal, outputting the divided signals through second and third ports, combining signals received through the second and third ports according to phases of the signals, and outputting the combined signal through the first port or as an output signal of the RF filter through a fourth port
Implementation Method 2
a phase shifter having one end connected to another end of the second filter and having another end that is opened, wherein the phase shifter dynamically adjusts phase variation of a signal through the second filter
Implementation Method 3
a first filter unit has a first port connected to the second port of the coupler and a second port connected to the third port of the coupler, for having a predetermined frequency filtering characteristic
Data Source
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AI summary
The present invention relates to a radio frequency filter comprising a coupler (310) for receiving an input signal through a first port, dividing the input signal, outputting the divided signals through second and third ports, combining signals received through the second and third ports according to phases of the signals, and outputting the combined signal through the first port or as an output signal of the RF filter through a fourth port; and a first filter unit (320) having a first port connected to the second port of the coupler and a second port connected to the third port of the coupler, for having a predetermined frequency filtering characteristic, wherein the first filter unit comprises a first filter (3210) having one end connected to the first port of the first filter unit and the other end that is opened, a second filter (3220) having one end connected to the second port of the first filter unit and a phase shifter (3230) having one end connected to the other end of the second filter and the other end that is opened.