Multilayer RF Filter Substrate Layout to Suppress Stray Capacitance
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Solution Overview
Problem
Conventional multilayer substrates with series LC circuit sections experience stray capacitance issues due to parallel capacitors, which can disrupt desired filter characteristics in radio-frequency applications.
Innovation Solution
The multilayer substrate design includes a specific arrangement of first and second capacitor electrodes and inductors on a dielectric substrate, where the second capacitor electrodes overlap the first electrodes, and inductors are connected in series with capacitors to minimize stray capacitance, allowing for effective suppression of stray capacitance and achieving desired filter characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If parallel capacitors are disposed in a multilayer substrate, then filter characteristics can be achieved, but stray capacitance arises between the additional parallel capacitor and ground
Solution Approach 1:
The patent transitions from planar capacitor arrangement to three-dimensional stacking, where capacitor electrodes are arranged in multiple layers along the thickness direction of the substrate. This vertical arrangement allows capacitors to be positioned above each other rather than side-by-side, reducing lateral proximity to ground planes and minimizing stray capacitance while preserving filtering functionality.
Solution Approach 2:
The patent implements nested capacitor structures where capacitor electrodes are embedded within the substrate layers, with inner capacitor electrodes surrounded by outer electrodes or ground planes at different vertical levels. This nesting approach allows compact integration while controlling parasitic effects through careful design of the nested geometry and spacing.
2Adaptability or versatility
If additional parallel capacitors are used to block direct current signals, then DC blocking function is achieved, but stray capacitance disrupts desired filter characteristics
Solution Approach 1:
The patent combines the DC blocking function and AC filtering function into a single integrated capacitor structure. By designing capacitors with specific electrode configurations and dielectric materials, the same capacitor component simultaneously blocks DC signals and provides frequency-selective filtering for AC signals, eliminating the need for separate additional capacitors that would introduce stray capacitance.
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 design effectively suppresses stray capacitance, enabling the multilayer substrate to function as high-pass or low-pass filters with predetermined frequency bands, enhancing the performance of radio-frequency front-end circuits and communication devices.
Implementation Method 1
Electrodes of the pair of first capacitor electrodes constitute a first capacitor electrically connected between the input/output electrode and the ground electrode
Implementation Method 2
a dielectric substrate
Implementation Method 3
The first inductor is electrically connected between the input/output electrode and the ground electrode. The second inductor is connected parallel to the first inductor
Data Source
AI summary
A multilayer substrate includes a pair of first capacitor electrodes, a pair of second capacitor electrodes, and a dielectric substrate. Electrodes of the pair of first capacitor electrodes are disposed in dielectric substrate so as to face each other in a thickness direction of the dielectric substrate. Electrodes of the pair of second capacitor electrodes are disposed in the dielectric substrate so as to face each other in the thickness direction. A first element and a second element that are disposed in or on the dielectric substrate, and the pair of second capacitor electrodes, the pair of first capacitor electrodes, and a ground electrode that are disposed in the dielectric substrate are arranged in the stated order in the thickness direction. The pair of second capacitor electrodes at least partially overlaps the pair of first capacitor electrodes when viewed in plan in the thickness direction.