RF Low-Pass Filter Using Ground Via Inductance to Cut Cost
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Solution Overview
Problem
The high cost of inductor components in low-pass filters used in wireless communication systems to suppress harmonics, particularly second and third harmonics, is a significant challenge, as the cost of cascading inductors is higher than capacitors, and existing solutions are costly and inefficient.
Innovation Solution
Replacing the filter inductor component with a ground via, which generates parasitic inductance, and adjusting its parameters to achieve equivalent inductive effects, thereby reducing the number of inductor components and costs while maintaining filtering performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional inductor components are used in low-pass filters, then filtering performance can be achieved, but the cost and area of the filter increase significantly
Solution Approach 1:
The patent replaces expensive inductor components with ground vias that have parasitic inductance. The ground via is a simple, low-cost structure consisting of a conductive pad connected to the ground plane through a via hole, eliminating the need for costly discrete inductor components while maintaining the necessary inductive effect for filtering performance
Solution Approach 2:
The patent substitutes the mechanical inductor component with an electrical structure (ground via) that exhibits parasitic inductance. Instead of using a dedicated inductor component, the design utilizes the inherent parasitic inductance of the ground via and its connection path to achieve the same filtering function, thereby reducing cost and complexity
2Measurement precision
If multiple inductor components are used to achieve desired resonance frequencies, then filtering accuracy improves, but the device complexity and cost increase
Solution Approach 1:
The ground via serves multiple functions simultaneously: it provides the necessary ground connection, introduces parasitic inductance for resonance frequency control, and eliminates the need for separate inductor components. This multi-functionality reduces the overall component count while maintaining filtering accuracy
Solution Approach 2:
The patent controls resonance frequency by adjusting parameters of the ground via structure, such as via hole dimensions, pad size, and distance from the capacitor, rather than changing the number of components. This allows precise tuning of resonance frequencies using a minimal component set
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 approach reduces the area and cost of filter components, maintains filtering performance, and allows for flexible adjustment of parasitic inductance to effectively filter out harmonics in radio frequency signals, improving the efficiency and cost-effectiveness of the filtering process.
Implementation Method 1
The first ground via generates a parasitic inductance effect, that is, is equivalent to a parasitic inductor, and a conducting wire between the first ground via and the first filter capacitor also generates a parasitic inductor. These parasitic inductors may be used as inductors during resonance.
Data Source
AI summary
A filter includes: an input terminal configured to receive a radio frequency signal, and an output terminal of the filter configured to output the radio frequency signal obtained after filtering. The filter further includes a first filter capacitor and a first ground via. The first filter capacitor is disposed in a substrate or on a surface of a substrate. A first terminal of the first filter capacitor is coupled to the input terminal or the output terminal of the filter, a second terminal of the first filter capacitor is coupled to a terminal of the first ground via disposed in the substrate, and another terminal of the first ground via is coupled to a ground.