Tunable RF Bandpass Filter With Variable Cross-Coupling Zeros
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Solution Overview
Problem
Existing RF filtering technologies are large, lack high power handling, slow in tuning speed, and limited in selectivity, failing to support newer waveforms with improved tuning speeds and wider bandwidths.
Innovation Solution
A tunable RF bandpass filter with variable cross-coupling using GaN switches and tunable capacitors, allowing for agile co-location filter performance in a small form factor, featuring four shunt resonators, inductive and capacitive coupling elements, and two cross-coupling circuits to generate transmission zeros for improved selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional RF filtering technologies are used, then the filter can provide basic frequency selection, but the filter size becomes large and power handling capability is limited
Solution Approach 1:
The patent employs GaN (gallium nitride) technology to fundamentally change the material parameters of the filter components. GaN switches and tunable capacitors enable high power handling capability while maintaining a compact form factor, directly resolving the contradiction between power handling and filter size.
Solution Approach 2:
The filter utilizes composite construction combining GaN switches, tunable capacitors, inductive coupling elements, and capacitive coupling elements in an integrated circuit design. This composite approach enables simultaneous achievement of high power handling, compact size, and agile tuning performance.
2Speed
If traditional filter designs are used, then the structure is simple, but the tuning speed is slow and bandwidth support is limited
Solution Approach 1:
The patent implements dynamic tuning capability through GaN switches and tunable capacitors that can rapidly adjust the filter's center frequency and bandwidth. The cross-coupling circuits with variable coupling coefficients enable real-time adaptation to different waveform requirements, achieving fast tuning speeds despite increased structural complexity.
Solution Approach 2:
The filter design incorporates multiple functions within a single device: frequency selection, agile tuning, bandwidth adjustment, and high power handling. The cross-coupling circuits serve dual purposes of frequency synthesis and selectivity enhancement, reducing the need for separate components and mitigating complexity concerns.
3Reliability
If basic filter design is used, then the device is compact, but the selectivity and rejection performance are insufficient
Solution Approach 1:
The patent introduces cross-coupling circuits as intermediary elements between the resonators. These circuits generate transmission zeros in both low and high rejection bands, significantly enhancing selectivity and rejection performance. The cross-coupling acts as a mediator that improves filter performance without requiring additional external components.
Solution Approach 2:
The filter is segmented into multiple functional blocks: shunt resonators for frequency selection, inductive coupling elements for energy transfer, capacitive coupling elements for impedance matching, and cross-coupling circuits for selectivity enhancement. This segmentation allows each component to be optimized independently while contributing to overall high selectivity performance.
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
Enables high power handling, fast tuning speeds, and consistent selectivity across a wide frequency range, supporting newer waveforms with a compact design.
Implementation Method 1
a plurality of shunt resonators coupled in series and configured to allow signals within a range of frequencies to pass
Implementation Method 2
a cross-coupling circuit connected to the plurality of shunt resonators and configured to generate a first transmission zero in a low rejection band of the bandpass filter and generate a second transmission zero in a high rejection band of the bandpass filter
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A bandpass filter comprising: a plurality of shunt resonators connected in series and configured to allow signals within a range of frequencies to pass; and a cross-coupling circuits connected to the plurality of shunt resonators and configured to generate a first transmission zeros in a low rejection band of the bandpass filter and generate a second transmission zero in a high rejection band of the bandpass filter.