PCB Interconnection via Inset-Fed Patches for Millimeter Wave
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Solution Overview
Problem
Conventional automotive RADAR systems operating at millimeter wave frequencies face high radiation and dielectric loss, absorption loss, and challenges in testing and interconnection due to the separation of antenna and radio frequency chips on different printed circuit boards, which results in costly and bulky solutions.
Innovation Solution
A device and method for interconnecting printed circuit boards at millimeter wave frequencies using a primary and secondary printed circuit board with inset-fed patches and plated through holes, coupled via a metal interconnection module with cut-out sections and slots to efficiently transfer electromagnetic energy, eliminating the need for costly coaxial cables and bulky waveguides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coaxial cable assemblies are used to connect printed circuit boards, then signal transmission is achieved, but loss increases and cost increases at millimeter wave frequencies
Solution Approach 1:
The patent introduces an intermediary coupling structure consisting of facing patches on adjacent PCBs that enables direct electromagnetic coupling between the boards. This intermediary mechanism replaces the traditional coaxial cable connector, allowing signal transfer through capacitive and inductive coupling between the patches, thereby eliminating the high losses associated with coaxial cables at millimeter wave frequencies.
Solution Approach 2:
The patent replaces the mechanical connection system (coaxial cable assemblies with connectors) with an electromagnetic field-based coupling system. The facing patches create an electromagnetic coupling field that transfers signals between PCBs without physical contact, substituting mechanical insertion and connection with field-based energy transfer, which significantly reduces signal loss at millimeter wave frequencies.
2Reliability
If standard waveguides with big flanges are used for interconnection, then signal transmission is achieved, but device size increases
Solution Approach 1:
The patent transitions from three-dimensional waveguide structures with large flanges to a two-dimensional planar coupling interface. The facing patches are positioned on adjacent PCB surfaces, utilizing the space between boards rather than requiring large lateral flanges. This dimensional transformation enables compact integration while maintaining effective signal transmission through electromagnetic coupling.
Solution Approach 2:
The patent extracts the essential function of signal transmission from the bulky waveguide structure and implements it through minimalistic facing patches on PCBs. By taking out only the necessary electromagnetic coupling capability and removing the unnecessary large flanges and waveguide enclosure, the solution achieves signal transmission with dramatically reduced device volume.
3Reliability
If conventional connectors with precise cavities are used, then connection is achieved, but manufacturing complexity increases and cost increases
Solution Approach 1:
The patent employs simple, inexpensive facing patches that can be manufactured using standard PCB fabrication processes rather than requiring complex precision-machined connectors. These patches are essentially copper traces on the PCB surface, which are created during normal PCB manufacturing, eliminating the need for separate precision connector fabrication and assembly steps.
Solution Approach 2:
The facing patches serve multiple functions: they act as signal transmission elements, provide impedance matching, and enable mechanical alignment between PCBs. This multi-functionality consolidates what would otherwise require separate components (connectors, alignment features, signal paths) into a single integrated structure, thereby reducing manufacturing complexity.
4Ease of manufacture
If plated copper thickness inside PCB cavity is not controlled, then manufacturing is simplified, but resonance frequency shifts and signal loss increases
Solution Approach 1:
The patent utilizes precisely controlled parameters of the facing patches including their dimensions, spacing, and position relative to ground planes. By carefully designing these geometric parameters, the solution achieves impedance matching and resonant frequency control without requiring variable plated copper thickness. The parameters are optimized during design to work with standard PCB manufacturing tolerances.
Solution Approach 2:
The patent replaces the mechanical control method of adjusting plated copper thickness with an electromagnetic design approach using patch geometry and positioning. Instead of relying on precise metal deposition control, the solution uses precisely calculated patch dimensions and spacing to achieve the desired electrical characteristics, which are more easily controlled during standard PCB fabrication.
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 solution achieves low-loss, efficient signal propagation and interconnection between printed circuit boards, reducing size and cost while maintaining high-frequency performance, with insertion loss as low as 0.20 dB across a wide bandwidth.
Implementation Method 1
an interconnection module for coupling an electromagnetic energy from the primary printed circuit board to the secondary printed circuit board
Implementation Method 2
a first arrangement of plated through holes (ground vias) surrounding the primary high frequency transmission line, a second arrangement of plated through holes (ground vias) surrounding the first inset-fed patch. Further, the first arrangement of plated through holes (ground vias), and the second arrangement of plated through holes (ground vias) form a ground connection
Data Source
AI summary
Disclosed is a method and device for interconnection of printed circuit boards operating at millimeter wave frequency band. The device comprises a primary printed circuit board, a secondary printed circuit board, an interconnection module for coupling electromagnetic energy from the primary printed circuit board to the secondary printed circuit board. The primary printed circuit board further comprising a primary top dielectric layer, specific via arrangements, a radio frequency chip, a primary high frequency transmission line connected to the radio frequency chip at one end and other end to a first inset-fed patch. The secondary printed circuit board further comprising a secondary top dielectric layer, specific via arrangements, a printed array antenna, a secondary high frequency transmission line connected to printed array antenna at one end, and other end to a second inset-fed patch. The interconnection module further comprising a first cut-out section, a second cut-out section and a slot.