Band-Pass Filter Topology for Harmonic Attenuation and Sharp Cutoff
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Solution Overview
Problem
Existing band pass filters face challenges in downsizing and achieving excellent cut-off characteristics for frequency bands adjacent to the main frequency band, particularly in harmonic frequency attenuation, due to the increasing and diversifying frequency bands used in electronic devices.
Innovation Solution
A band pass filter design incorporating a resonator with series and parallel inductors and capacitors, including a low pass filter function through capacitors connected to ground, and a band stop filter function using inductors and capacitors in series, to effectively cut off adjacent low and high frequency bands and reduce harmonic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional band pass filter designs are used, then the filter can pass the main frequency band, but the cut-off characteristics for adjacent frequency bands and harmonic attenuation are insufficient
Solution Approach 1:
The patent combines multiple filter functions (band pass, low pass, band stop) into a single integrated filter structure. The resonator circuit incorporates capacitors connected to ground for low pass filtering and series LC combinations for band stop filtering, all within one unified circuit topology that processes the RF signal through a single path.
Solution Approach 2:
The filter structure performs multiple functions simultaneously: it passes the main frequency band (band pass), attenuates adjacent low frequency bands (low pass), and rejects specific harmonic frequencies (band stop). This multi-functionality is achieved through the strategic placement of capacitors and inductors that create different filtering effects at different frequency ranges within the same circuit.
2Volume of moving object
If the filter structure is simplified for downsizing, then the device size is reduced, but the harmonic frequency attenuation characteristic deteriorates
Solution Approach 1:
The filter is segmented into distinct functional sections within the circuit: the resonator section for band pass filtering, capacitors connected to ground nodes for low pass filtering, and series LC combinations for band stop filtering. This segmentation allows each component to contribute specifically to different aspects of signal filtering, achieving comprehensive frequency selection in a compact arrangement.
Solution Approach 2:
Different parts of the circuit are designed with specific local characteristics: capacitors are strategically placed at specific nodes to provide low pass filtering at those locations, while series LC combinations are positioned to target specific harmonic frequencies. This local optimization of filtering properties throughout the circuit enables effective harmonic attenuation without requiring a large overall structure.
3Reliability
If additional filter components are added to improve cut-off characteristics, then the filtering performance is enhanced, but the device complexity increases
Solution Approach 1:
The patent merges multiple filtering mechanisms into a single integrated circuit topology where capacitors and inductors work together in unified configurations. Rather than adding separate filter modules, the design incorporates low pass and band stop functions directly into the resonator circuit structure, sharing common components and signal paths.
Solution Approach 2:
The filter circuit is designed to perform multiple filtering operations through a single unified structure. The same capacitors and inductors that provide band pass characteristics also contribute to low pass and band stop filtering, allowing one circuit to replace what would traditionally require multiple separate filter stages.
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 proposed filter design enhances cut-off characteristics for both low and high frequency bands adjacent to the main frequency band, improving harmonic attenuation and maintaining symmetric impedance, thus addressing the need for downsizing and advanced filtering in electronic devices.
Implementation Method 1
a resonator including a first inductor and a first capacitor coupled in series between a first port and a second port, a second inductor coupled in parallel with the resonator
Implementation Method 2
a resonator including a first inductor and a first capacitor coupled in series between an input port and an output port of the band pass filter
Implementation Method 3
a third capacitor coupled between one end of the second capacitor and the ground to perform a low pass filter function
Implementation Method 4
a third capacitor and the third inductor may be configured to perform a band stop filter function
Data Source
AI summary
A band pass filter includes a resonator including a first inductor and a first capacitor coupled in series between a first port and a second port, a second inductor coupled in parallel with the resonator, a second capacitor coupled in parallel with the resonator, and a third capacitor coupled between one end of the second capacitor and the ground to perform a low pass filter function.