LC Resonator Filter Layout for Spurious Signal Shifting
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Solution Overview
Problem
Unintended spurious signals are generated in the non-pass band of low pass filters due to stray capacitance and structural asymmetry, leading to deterioration of attenuation characteristics, particularly in communication devices using microwave and millimeter wave bands, which can degrade communication quality.
Innovation Solution
A filter device with an LC parallel resonator structure includes a capacitor for spurious adjustment between the inductors and capacitors, with a larger capacitance than stray capacitance, to shift spurious signals out of the target frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low pass filter is constructed with conventional inductor and capacitor elements, then the filter achieves basic frequency selection functionality, but spurious signals are generated in the non-pass band due to stray capacitance and structural asymmetry, causing deterioration of attenuation characteristics
Solution Approach 1:
A ground electrode is introduced as an intermediary element between the signal path elements. This ground electrode serves as a mediator that provides a reference potential and suppresses unwanted electromagnetic fields, thereby reducing spurious signal generation while maintaining the filter's attenuation characteristics in the non-pass band
Solution Approach 2:
The patent applies different structural configurations to different parts of the filter. Specifically, the inductor and capacitor elements are designed with asymmetric structures where certain electrodes are intentionally left unconnected to the insulating substrate, creating local variations in electrical properties that cancel out spurious signals while preserving the desired frequency response
2Ease of manufacture
If the filter structure is simplified for ease of manufacture, then production cost and complexity are reduced, but spurious signals increase due to manufacturing variations and structural asymmetry
Solution Approach 1:
The patent deliberately introduces asymmetric structural elements into the filter design. The inductor and capacitor electrodes are configured with intentional asymmetries that counterbalance manufacturing variations, allowing the filter to maintain consistent performance and reduce spurious signals even when produced with standard manufacturing tolerances
Solution Approach 2:
The patent modifies specific structural parameters of the filter elements, such as the positioning and connection status of electrodes relative to the insulating substrate. By changing these geometric parameters, the filter achieves better suppression of spurious signals without requiring complex manufacturing processes
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 solution effectively prevents or reduces the deterioration of attenuation characteristics by shifting spurious signals to non-pass bands, ensuring consistent performance in microwave and millimeter wave frequency ranges.
Implementation Method 1
unintended spurious may be generated in a non-pass band on a higher frequency side than a pass band by the stray capacitance of an inductor that constitutes a resonance circuit
Implementation Method 2
an inductor that constitutes a resonance circuit
Data Source
AI summary
A filter device includes an input terminal, an output terminal, and a resonator connected to the input terminal and the output terminal. The resonator includes a first terminal connected to the input terminal, a second terminal connected to the output terminal, first and second inductors, and first to third capacitors. A first end of the first inductor is connected to the first terminal. The second inductor has a first end connected to the second terminal and a second end connected to a second end of the second inductor. A first end of the first capacitor is connected to the first terminal. The second capacitor has a first end connected to the second terminal and a second end connected to the second end of the capacitor. The third capacitor is connected between a second end of the first inductor and a second end of the first capacitor.