Hybrid Diplex Filter Tuning for Re-Resonance Control
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Solution Overview
Problem
Existing diplex bandstop filters in CATV systems face challenges in achieving a flat upper passband due to large capacitors and coils, leading to multiple re-resonances in the highpass leg, resulting in poor return loss and increased delay.
Innovation Solution
A hybrid diplex bandstop filter design that includes a lowpass filter circuit, a bandstop circuit, and a highpass filter circuit, with a tuning circuit that relocates at least one re-resonance within the lowpass range to either within the blocked frequency range or outside the industry-specified upper limit in the highpass range, using inductors and capacitors in specific configurations to minimize parasitics and improve bandwidth utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If typical minimum inductor or capacitor design techniques are used in the lowpass leg, then the filter structure is simple, but multiple re-resonances occur in the upper passband causing poor return loss and increased delay
Solution Approach 1:
The patent applies parameter changes by modifying the inductor and capacitor values in the lowpass filter section. Specifically, it uses a minimum inductor design with a carefully selected inductance value (e.g., 5.6 µH) and compensating capacitor values to push re-resonances above the upper passband frequency range, thereby eliminating the harmful re-resonances while maintaining a relatively simple filter structure.
Solution Approach 2:
The patent introduces tuning capability to dynamically adjust the filter characteristics. Variable capacitors or adjustable inductors are incorporated to allow the filter to be tuned for different frequency ranges and impedance values, enabling the system to adapt to varying conditions and eliminate re-resonances in different operating scenarios.
2Device complexity
If typical minimum inductor or capacitor design techniques are used in the lowpass leg, then the filter structure is simple, but delay is increased
Solution Approach 1:
The patent optimizes the inductor and capacitor parameter values to minimize signal delay. By selecting specific inductance values (e.g., 5.6 µH) and corresponding capacitor values that push re-resonances above the passband, the filter achieves faster response times and reduced group delay while maintaining structural simplicity.
3Reliability
If large capacitors and coils are used to make up the low frequency lowpass filter, then the filter can block the desired frequency range, but multiple re-resonances are created in the upper passband
Solution Approach 1:
The patent changes the parameter values of inductors and capacitors to eliminate harmful re-resonances. Instead of using arbitrarily large values, it specifies optimized values (e.g., 5.6 µH inductors with specific capacitor values) that push the re-resonance frequencies above the upper passband, thereby blocking the desired frequency range without creating harmful resonances in the operational band.
Solution Approach 2:
The patent converts the potentially harmful re-resonances into beneficial characteristics by positioning them above the upper passband. The re-resonances that would normally cause problems in the passband are deliberately shifted to frequencies beyond the operational range, where they can serve as additional stopband rejection without interfering with signal transmission.
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 hybrid filter design effectively reduces re-resonances, enhancing return loss and reducing delay by relocating resonances outside the usable bandwidth, thereby improving the filter's performance and adaptability to varying industry standards.
Implementation Method 1
a lowpass filter circuit which allows a first range of frequencies to pass through the filter from an input to an output
Implementation Method 2
a bandstop circuit which blocks a second range of frequencies from passing through the filter from the input to an output
Implementation Method 3
a highpass filter circuit which allows a third range of frequencies to pass through the filter from the input to an output
Implementation Method 4
a tuning circuit which tunes at least one re-resonance of a frequency within the first range of frequencies to either within the second range of frequencies or outside an industry specified upper limit within the third range of frequencies
Data Source
AI summary
A hybrid diplex bandstop filter includes a lowpass filter circuit which passes a first range of frequencies and a highpass filter circuit passes a third range of frequencies. The filter blocks a second range of frequencies. The third range of frequencies is higher than the second range and the first range. A tuning circuit tunes at least one re-resonance of a frequency inside the first range of frequencies to either within the second range of frequencies or outside an industry specified upper limit which is in the third range of frequencies.