PCB Resistive Patch Geometry for Stable Millimeter-Wave Impedance
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Solution Overview
Problem
Conventional resistive devices for millimeter-wave applications face challenges due to parasitic capacitance and inductance, which lead to frequency-dependent impedance and signal mismatch at high frequencies, limiting their operational range and efficiency.
Innovation Solution
The use of novel geometrical shapes for printed resistive patches, such as elliptical, circular, and polygonal shapes, to balance parasitic reactance, thereby increasing the frequency range and reducing parasitic effects, which are absorbed into the circuit design rather than canceled out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional planar film resistors are used in PCBs, then manufacturing is simple and cost-effective, but parasitic capacitance and inductance increase at high frequencies, causing frequency-dependent impedance and signal mismatch
Solution Approach 1:
The patent applies curvature by replacing conventional rectangular planar resistive traces with circular or annular geometries. This curved configuration redistributes the current flow path and reduces the effective area for parasitic capacitance formation between adjacent trace sections, thereby improving frequency response stability while maintaining PCB integration benefits
Solution Approach 2:
The patent introduces asymmetric spacing and positioning of resistive elements within the circular/annular pattern, optimizing the distribution of parasitic effects. By strategically placing resistive sections at specific angular positions and varying their dimensions asymmetrically, the design compensates for parasitic inductance and capacitance variations across the frequency range
2Power
If the physical length of resistive elements is increased to achieve desired resistance values, then power handling improves, but distributed inductance increases, degrading high-frequency performance
Solution Approach 1:
The patent divides the total resistive path into multiple discrete resistive sections arranged in series around the circular or annular structure. Each segment contributes to the total resistance while the distributed geometry reduces the cumulative parasitic inductance compared to a single continuous linear trace of equivalent length
Solution Approach 2:
The patent transitions from a one-dimensional linear resistive trace to a two-dimensional circular or annular configuration. This dimensional change allows the resistive path to be distributed over a larger area with optimized current distribution, reducing the effective inductance per unit resistance while maintaining power handling capability
3Reliability
If discrete resistive components are used to achieve precise resistance values, then frequency response improves, but device complexity and space requirements increase at millimeter-wave frequencies
Solution Approach 1:
The patent merges multiple resistive functions into a single integrated PCB-trace-based structure with circular or annular geometry. This unified design provides precise resistance values and improved frequency response that would otherwise require multiple discrete components, thereby reducing device complexity and space requirements at millimeter-wave frequencies
Data Source
AI summary
According to an aspect, there is provided a printed circuit board-based resistive device. The resistive device comprises, arranged on a substrate of the printed circuit board of the printed circuit board: a first conductive pad; a second conductive pad; a resistive patch having a first longitudinal end connected to the first conductive pad and a second longitudinal end connected to the second conductive pad, wherein a width of the resistive patch varies along a length of the resistive patch and has a maximum at a point between the first and second longitudinal ends.